// SPDX-License-Identifier: GPL-2.0
#include <linux/ceph/ceph_debug.h>

#include <linux/backing-dev.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/writeback.h>    /* generic_writepages */
#include <linux/slab.h>
#include <linux/pagevec.h>
#include <linux/task_io_accounting_ops.h>
#include <linux/signal.h>
#include <linux/iversion.h>
#include <linux/ktime.h>

#include "super.h"
#include "mds_client.h"
#include "cache.h"
#include "metric.h"
#include <linux/ceph/osd_client.h>
#include <linux/ceph/striper.h>

/*
 * Ceph address space ops.
 *
 * There are a few funny things going on here.
 *
 * The page->private field is used to reference a struct
 * ceph_snap_context for _every_ dirty page.  This indicates which
 * snapshot the page was logically dirtied in, and thus which snap
 * context needs to be associated with the osd write during writeback.
 *
 * Similarly, struct ceph_inode_info maintains a set of counters to
 * count dirty pages on the inode.  In the absence of snapshots,
 * i_wrbuffer_ref == i_wrbuffer_ref_head == the dirty page count.
 *
 * When a snapshot is taken (that is, when the client receives
 * notification that a snapshot was taken), each inode with caps and
 * with dirty pages (dirty pages implies there is a cap) gets a new
 * ceph_cap_snap in the i_cap_snaps list (which is sorted in ascending
 * order, new snaps go to the tail).  The i_wrbuffer_ref_head count is
 * moved to capsnap->dirty. (Unless a sync write is currently in
 * progress.  In that case, the capsnap is said to be "pending", new
 * writes cannot start, and the capsnap isn't "finalized" until the
 * write completes (or fails) and a final size/mtime for the inode for
 * that snap can be settled upon.)  i_wrbuffer_ref_head is reset to 0.
 *
 * On writeback, we must submit writes to the osd IN SNAP ORDER.  So,
 * we look for the first capsnap in i_cap_snaps and write out pages in
 * that snap context _only_.  Then we move on to the next capsnap,
 * eventually reaching the "live" or "head" context (i.e., pages that
 * are not yet snapped) and are writing the most recently dirtied
 * pages.
 *
 * Invalidate and so forth must take care to ensure the dirty page
 * accounting is preserved.
 */

#define CONGESTION_ON_THRESH(congestion_kb) (congestion_kb >> (PAGE_SHIFT-10))
#define CONGESTION_OFF_THRESH(congestion_kb)                            \
        (CONGESTION_ON_THRESH(congestion_kb) -                          \
         (CONGESTION_ON_THRESH(congestion_kb) >> 2))

static inline struct ceph_snap_context *page_snap_context(struct page *page)
{
        if (PagePrivate(page))
                return (void *)page->private;
        return NULL;
}

/*
 * Dirty a page.  Optimistically adjust accounting, on the assumption
 * that we won't race with invalidate.  If we do, readjust.
 */
static int ceph_set_page_dirty(struct page *page)
{
        struct address_space *mapping = page->mapping;
        struct inode *inode;
        struct ceph_inode_info *ci;
        struct ceph_snap_context *snapc;
        int ret;

        if (unlikely(!mapping))
                return !TestSetPageDirty(page);

        if (PageDirty(page)) {
                dout("%p set_page_dirty %p idx %lu -- already dirty\n",
                     mapping->host, page, page->index);
                BUG_ON(!PagePrivate(page));
                return 0;
        }

        inode = mapping->host;
        ci = ceph_inode(inode);

        /* dirty the head */
        spin_lock(&ci->i_ceph_lock);
        BUG_ON(ci->i_wr_ref == 0); // caller should hold Fw reference
        if (__ceph_have_pending_cap_snap(ci)) {
                struct ceph_cap_snap *capsnap =
                                list_last_entry(&ci->i_cap_snaps,
                                                struct ceph_cap_snap,
                                                ci_item);
                snapc = ceph_get_snap_context(capsnap->context);
                capsnap->dirty_pages++;
        } else {
                BUG_ON(!ci->i_head_snapc);
                snapc = ceph_get_snap_context(ci->i_head_snapc);
                ++ci->i_wrbuffer_ref_head;
        }
        if (ci->i_wrbuffer_ref == 0)
                ihold(inode);
        ++ci->i_wrbuffer_ref;
        dout("%p set_page_dirty %p idx %lu head %d/%d -> %d/%d "
             "snapc %p seq %lld (%d snaps)\n",
             mapping->host, page, page->index,
             ci->i_wrbuffer_ref-1, ci->i_wrbuffer_ref_head-1,
             ci->i_wrbuffer_ref, ci->i_wrbuffer_ref_head,
             snapc, snapc->seq, snapc->num_snaps);
        spin_unlock(&ci->i_ceph_lock);

        /*
         * Reference snap context in page->private.  Also set
         * PagePrivate so that we get invalidatepage callback.
         */
        BUG_ON(PagePrivate(page));
        page->private = (unsigned long)snapc;
        SetPagePrivate(page);

        ret = __set_page_dirty_nobuffers(page);
        WARN_ON(!PageLocked(page));
        WARN_ON(!page->mapping);

        return ret;
}

/*
 * If we are truncating the full page (i.e. offset == 0), adjust the
 * dirty page counters appropriately.  Only called if there is private
 * data on the page.
 */
static void ceph_invalidatepage(struct page *page, unsigned int offset,
                                unsigned int length)
{
        struct inode *inode;
        struct ceph_inode_info *ci;
        struct ceph_snap_context *snapc = page_snap_context(page);

        inode = page->mapping->host;
        ci = ceph_inode(inode);

        if (offset != 0 || length != PAGE_SIZE) {
                dout("%p invalidatepage %p idx %lu partial dirty page %u~%u\n",
                     inode, page, page->index, offset, length);
                return;
        }

        ceph_invalidate_fscache_page(inode, page);

        WARN_ON(!PageLocked(page));
        if (!PagePrivate(page))
                return;

        dout("%p invalidatepage %p idx %lu full dirty page\n",
             inode, page, page->index);

        ceph_put_wrbuffer_cap_refs(ci, 1, snapc);
        ceph_put_snap_context(snapc);
        page->private = 0;
        ClearPagePrivate(page);
}

static int ceph_releasepage(struct page *page, gfp_t g)
{
        dout("%p releasepage %p idx %lu (%sdirty)\n", page->mapping->host,
             page, page->index, PageDirty(page) ? "" : "not ");

        /* Can we release the page from the cache? */
        if (!ceph_release_fscache_page(page, g))
                return 0;

        return !PagePrivate(page);
}

/*
 * Read some contiguous pages.  If we cross a stripe boundary, shorten
 * *plen.  Return number of bytes read, or error.
 */
static int ceph_sync_readpages(struct ceph_fs_client *fsc,
                               struct ceph_vino vino,
                               struct ceph_file_layout *layout,
                               u64 off, u64 *plen,
                               u32 truncate_seq, u64 truncate_size,
                               struct page **pages, int num_pages,
                               int page_align)
{
        struct ceph_osd_client *osdc = &fsc->client->osdc;
        struct ceph_osd_request *req;
        int rc = 0;

        dout("readpages on ino %llx.%llx on %llu~%llu\n", vino.ino,
             vino.snap, off, *plen);
        req = ceph_osdc_new_request(osdc, layout, vino, off, plen, 0, 1,
                                    CEPH_OSD_OP_READ, CEPH_OSD_FLAG_READ,
                                    NULL, truncate_seq, truncate_size,
                                    false);
        if (IS_ERR(req))
                return PTR_ERR(req);

        /* it may be a short read due to an object boundary */
        osd_req_op_extent_osd_data_pages(req, 0,
                                pages, *plen, page_align, false, false);

        dout("readpages  final extent is %llu~%llu (%llu bytes align %d)\n",
             off, *plen, *plen, page_align);

        rc = ceph_osdc_start_request(osdc, req, false);
        if (!rc)
                rc = ceph_osdc_wait_request(osdc, req);

        ceph_update_read_latency(&fsc->mdsc->metric, req->r_start_latency,
                                 req->r_end_latency, rc);

        ceph_osdc_put_request(req);
        dout("readpages result %d\n", rc);
        return rc;
}

/*
 * read a single page, without unlocking it.
 */
static int ceph_do_readpage(struct file *filp, struct page *page)
{
        struct inode *inode = file_inode(filp);
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
        int err = 0;
        u64 off = page_offset(page);
        u64 len = PAGE_SIZE;

        if (off >= i_size_read(inode)) {
                zero_user_segment(page, 0, PAGE_SIZE);
                SetPageUptodate(page);
                return 0;
        }

        if (ci->i_inline_version != CEPH_INLINE_NONE) {
                /*
                 * Uptodate inline data should have been added
                 * into page cache while getting Fcr caps.
                 */
                if (off == 0)
                        return -EINVAL;
                zero_user_segment(page, 0, PAGE_SIZE);
                SetPageUptodate(page);
                return 0;
        }

        err = ceph_readpage_from_fscache(inode, page);
        if (err == 0)
                return -EINPROGRESS;

        dout("readpage inode %p file %p page %p index %lu\n",
             inode, filp, page, page->index);
        err = ceph_sync_readpages(fsc, ceph_vino(inode),
                                  &ci->i_layout, off, &len,
                                  ci->i_truncate_seq, ci->i_truncate_size,
                                  &page, 1, 0);
        if (err == -ENOENT)
                err = 0;
        if (err < 0) {
                SetPageError(page);
                ceph_fscache_readpage_cancel(inode, page);
                if (err == -EBLACKLISTED)
                        fsc->blacklisted = true;
                goto out;
        }
        if (err < PAGE_SIZE)
                /* zero fill remainder of page */
                zero_user_segment(page, err, PAGE_SIZE);
        else
                flush_dcache_page(page);

        SetPageUptodate(page);
        ceph_readpage_to_fscache(inode, page);

out:
        return err < 0 ? err : 0;
}

static int ceph_readpage(struct file *filp, struct page *page)
{
        int r = ceph_do_readpage(filp, page);
        if (r != -EINPROGRESS)
                unlock_page(page);
        else
                r = 0;
        return r;
}

/*
 * Finish an async read(ahead) op.
 */
static void finish_read(struct ceph_osd_request *req)
{
        struct inode *inode = req->r_inode;
        struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
        struct ceph_osd_data *osd_data;
        int rc = req->r_result <= 0 ? req->r_result : 0;
        int bytes = req->r_result >= 0 ? req->r_result : 0;
        int num_pages;
        int i;

        dout("finish_read %p req %p rc %d bytes %d\n", inode, req, rc, bytes);
        if (rc == -EBLACKLISTED)
                ceph_inode_to_client(inode)->blacklisted = true;

        /* unlock all pages, zeroing any data we didn't read */
        osd_data = osd_req_op_extent_osd_data(req, 0);
        BUG_ON(osd_data->type != CEPH_OSD_DATA_TYPE_PAGES);
        num_pages = calc_pages_for((u64)osd_data->alignment,
                                        (u64)osd_data->length);
        for (i = 0; i < num_pages; i++) {
                struct page *page = osd_data->pages[i];

                if (rc < 0 && rc != -ENOENT) {
                        ceph_fscache_readpage_cancel(inode, page);
                        goto unlock;
                }
                if (bytes < (int)PAGE_SIZE) {
                        /* zero (remainder of) page */
                        int s = bytes < 0 ? 0 : bytes;
                        zero_user_segment(page, s, PAGE_SIZE);
                }
                dout("finish_read %p uptodate %p idx %lu\n", inode, page,
                     page->index);
                flush_dcache_page(page);
                SetPageUptodate(page);
                ceph_readpage_to_fscache(inode, page);
unlock:
                unlock_page(page);
                put_page(page);
                bytes -= PAGE_SIZE;
        }

        ceph_update_read_latency(&fsc->mdsc->metric, req->r_start_latency,
                                 req->r_end_latency, rc);

        kfree(osd_data->pages);
}

/*
 * start an async read(ahead) operation.  return nr_pages we submitted
 * a read for on success, or negative error code.
 */
static int start_read(struct inode *inode, struct ceph_rw_context *rw_ctx,
                      struct list_head *page_list, int max)
{
        struct ceph_osd_client *osdc =
                &ceph_inode_to_client(inode)->client->osdc;
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct page *page = lru_to_page(page_list);
        struct ceph_vino vino;
        struct ceph_osd_request *req;
        u64 off;
        u64 len;
        int i;
        struct page **pages;
        pgoff_t next_index;
        int nr_pages = 0;
        int got = 0;
        int ret = 0;

        if (!rw_ctx) {
                /* caller of readpages does not hold buffer and read caps
                 * (fadvise, madvise and readahead cases) */
                int want = CEPH_CAP_FILE_CACHE;
                ret = ceph_try_get_caps(inode, CEPH_CAP_FILE_RD, want,
                                        true, &got);
                if (ret < 0) {
                        dout("start_read %p, error getting cap\n", inode);
                } else if (!(got & want)) {
                        dout("start_read %p, no cache cap\n", inode);
                        ret = 0;
                }
                if (ret <= 0) {
                        if (got)
                                ceph_put_cap_refs(ci, got);
                        while (!list_empty(page_list)) {
                                page = lru_to_page(page_list);
                                list_del(&page->lru);
                                put_page(page);
                        }
                        return ret;
                }
        }

        off = (u64) page_offset(page);

        /* count pages */
        next_index = page->index;
        list_for_each_entry_reverse(page, page_list, lru) {
                if (page->index != next_index)
                        break;
                nr_pages++;
                next_index++;
                if (max && nr_pages == max)
                        break;
        }
        len = nr_pages << PAGE_SHIFT;
        dout("start_read %p nr_pages %d is %lld~%lld\n", inode, nr_pages,
             off, len);
        vino = ceph_vino(inode);
        req = ceph_osdc_new_request(osdc, &ci->i_layout, vino, off, &len,
                                    0, 1, CEPH_OSD_OP_READ,
                                    CEPH_OSD_FLAG_READ, NULL,
                                    ci->i_truncate_seq, ci->i_truncate_size,
                                    false);
        if (IS_ERR(req)) {
                ret = PTR_ERR(req);
                goto out;
        }

        /* build page vector */
        nr_pages = calc_pages_for(0, len);
        pages = kmalloc_array(nr_pages, sizeof(*pages), GFP_KERNEL);
        if (!pages) {
                ret = -ENOMEM;
                goto out_put;
        }
        for (i = 0; i < nr_pages; ++i) {
                page = list_entry(page_list->prev, struct page, lru);
                BUG_ON(PageLocked(page));
                list_del(&page->lru);

                dout("start_read %p adding %p idx %lu\n", inode, page,
                     page->index);
                if (add_to_page_cache_lru(page, &inode->i_data, page->index,
                                          GFP_KERNEL)) {
                        ceph_fscache_uncache_page(inode, page);
                        put_page(page);
                        dout("start_read %p add_to_page_cache failed %p\n",
                             inode, page);
                        nr_pages = i;
                        if (nr_pages > 0) {
                                len = nr_pages << PAGE_SHIFT;
                                osd_req_op_extent_update(req, 0, len);
                                break;
                        }
                        goto out_pages;
                }
                pages[i] = page;
        }
        osd_req_op_extent_osd_data_pages(req, 0, pages, len, 0, false, false);
        req->r_callback = finish_read;
        req->r_inode = inode;

        dout("start_read %p starting %p %lld~%lld\n", inode, req, off, len);
        ret = ceph_osdc_start_request(osdc, req, false);
        if (ret < 0)
                goto out_pages;
        ceph_osdc_put_request(req);

        /* After adding locked pages to page cache, the inode holds cache cap.
         * So we can drop our cap refs. */
        if (got)
                ceph_put_cap_refs(ci, got);

        return nr_pages;

out_pages:
        for (i = 0; i < nr_pages; ++i) {
                ceph_fscache_readpage_cancel(inode, pages[i]);
                unlock_page(pages[i]);
        }
        ceph_put_page_vector(pages, nr_pages, false);
out_put:
        ceph_osdc_put_request(req);
out:
        if (got)
                ceph_put_cap_refs(ci, got);
        return ret;
}


/*
 * Read multiple pages.  Leave pages we don't read + unlock in page_list;
 * the caller (VM) cleans them up.
 */
static int ceph_readpages(struct file *file, struct address_space *mapping,
                          struct list_head *page_list, unsigned nr_pages)
{
        struct inode *inode = file_inode(file);
        struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
        struct ceph_file_info *fi = file->private_data;
        struct ceph_rw_context *rw_ctx;
        int rc = 0;
        int max = 0;

        if (ceph_inode(inode)->i_inline_version != CEPH_INLINE_NONE)
                return -EINVAL;

        rc = ceph_readpages_from_fscache(mapping->host, mapping, page_list,
                                         &nr_pages);

        if (rc == 0)
                goto out;

        rw_ctx = ceph_find_rw_context(fi);
        max = fsc->mount_options->rsize >> PAGE_SHIFT;
        dout("readpages %p file %p ctx %p nr_pages %d max %d\n",
             inode, file, rw_ctx, nr_pages, max);
        while (!list_empty(page_list)) {
                rc = start_read(inode, rw_ctx, page_list, max);
                if (rc < 0)
                        goto out;
        }
out:
        ceph_fscache_readpages_cancel(inode, page_list);

        dout("readpages %p file %p ret %d\n", inode, file, rc);
        return rc;
}

struct ceph_writeback_ctl
{
        loff_t i_size;
        u64 truncate_size;
        u32 truncate_seq;
        bool size_stable;
        bool head_snapc;
};

/*
 * Get ref for the oldest snapc for an inode with dirty data... that is, the
 * only snap context we are allowed to write back.
 */
static struct ceph_snap_context *
get_oldest_context(struct inode *inode, struct ceph_writeback_ctl *ctl,
                   struct ceph_snap_context *page_snapc)
{
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_snap_context *snapc = NULL;
        struct ceph_cap_snap *capsnap = NULL;

        spin_lock(&ci->i_ceph_lock);
        list_for_each_entry(capsnap, &ci->i_cap_snaps, ci_item) {
                dout(" cap_snap %p snapc %p has %d dirty pages\n", capsnap,
                     capsnap->context, capsnap->dirty_pages);
                if (!capsnap->dirty_pages)
                        continue;

                /* get i_size, truncate_{seq,size} for page_snapc? */
                if (snapc && capsnap->context != page_snapc)
                        continue;

                if (ctl) {
                        if (capsnap->writing) {
                                ctl->i_size = i_size_read(inode);
                                ctl->size_stable = false;
                        } else {
                                ctl->i_size = capsnap->size;
                                ctl->size_stable = true;
                        }
                        ctl->truncate_size = capsnap->truncate_size;
                        ctl->truncate_seq = capsnap->truncate_seq;
                        ctl->head_snapc = false;
                }

                if (snapc)
                        break;

                snapc = ceph_get_snap_context(capsnap->context);
                if (!page_snapc ||
                    page_snapc == snapc ||
                    page_snapc->seq > snapc->seq)
                        break;
        }
        if (!snapc && ci->i_wrbuffer_ref_head) {
                snapc = ceph_get_snap_context(ci->i_head_snapc);
                dout(" head snapc %p has %d dirty pages\n",
                     snapc, ci->i_wrbuffer_ref_head);
                if (ctl) {
                        ctl->i_size = i_size_read(inode);
                        ctl->truncate_size = ci->i_truncate_size;
                        ctl->truncate_seq = ci->i_truncate_seq;
                        ctl->size_stable = false;
                        ctl->head_snapc = true;
                }
        }
        spin_unlock(&ci->i_ceph_lock);
        return snapc;
}

static u64 get_writepages_data_length(struct inode *inode,
                                      struct page *page, u64 start)
{
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_snap_context *snapc = page_snap_context(page);
        struct ceph_cap_snap *capsnap = NULL;
        u64 end = i_size_read(inode);

        if (snapc != ci->i_head_snapc) {
                bool found = false;
                spin_lock(&ci->i_ceph_lock);
                list_for_each_entry(capsnap, &ci->i_cap_snaps, ci_item) {
                        if (capsnap->context == snapc) {
                                if (!capsnap->writing)
                                        end = capsnap->size;
                                found = true;
                                break;
                        }
                }
                spin_unlock(&ci->i_ceph_lock);
                WARN_ON(!found);
        }
        if (end > page_offset(page) + PAGE_SIZE)
                end = page_offset(page) + PAGE_SIZE;
        return end > start ? end - start : 0;
}

/*
 * do a synchronous write on N pages
 */
static int ceph_sync_writepages(struct ceph_fs_client *fsc,
                                struct ceph_vino vino,
                                struct ceph_file_layout *layout,
                                struct ceph_snap_context *snapc,
                                u64 off, u64 len,
                                u32 truncate_seq, u64 truncate_size,
                                struct timespec64 *mtime,
                                struct page **pages, int num_pages)
{
        struct ceph_osd_client *osdc = &fsc->client->osdc;
        struct ceph_osd_request *req;
        int rc = 0;
        int page_align = off & ~PAGE_MASK;

        req = ceph_osdc_new_request(osdc, layout, vino, off, &len, 0, 1,
                                    CEPH_OSD_OP_WRITE, CEPH_OSD_FLAG_WRITE,
                                    snapc, truncate_seq, truncate_size,
                                    true);
        if (IS_ERR(req))
                return PTR_ERR(req);

        /* it may be a short write due to an object boundary */
        osd_req_op_extent_osd_data_pages(req, 0, pages, len, page_align,
                                false, false);
        dout("writepages %llu~%llu (%llu bytes)\n", off, len, len);

        req->r_mtime = *mtime;
        rc = ceph_osdc_start_request(osdc, req, true);
        if (!rc)
                rc = ceph_osdc_wait_request(osdc, req);

        ceph_update_write_latency(&fsc->mdsc->metric, req->r_start_latency,
                                  req->r_end_latency, rc);

        ceph_osdc_put_request(req);
        if (rc == 0)
                rc = len;
        dout("writepages result %d\n", rc);
        return rc;
}

/*
 * Write a single page, but leave the page locked.
 *
 * If we get a write error, mark the mapping for error, but still adjust the
 * dirty page accounting (i.e., page is no longer dirty).
 */
static int writepage_nounlock(struct page *page, struct writeback_control *wbc)
{
        struct inode *inode;
        struct ceph_inode_info *ci;
        struct ceph_fs_client *fsc;
        struct ceph_snap_context *snapc, *oldest;
        loff_t page_off = page_offset(page);
        int err, len = PAGE_SIZE;
        struct ceph_writeback_ctl ceph_wbc;

        dout("writepage %p idx %lu\n", page, page->index);

        inode = page->mapping->host;
        ci = ceph_inode(inode);
        fsc = ceph_inode_to_client(inode);

        /* verify this is a writeable snap context */
        snapc = page_snap_context(page);
        if (!snapc) {
                dout("writepage %p page %p not dirty?\n", inode, page);
                return 0;
        }
        oldest = get_oldest_context(inode, &ceph_wbc, snapc);
        if (snapc->seq > oldest->seq) {
                dout("writepage %p page %p snapc %p not writeable - noop\n",
                     inode, page, snapc);
                /* we should only noop if called by kswapd */
                WARN_ON(!(current->flags & PF_MEMALLOC));
                ceph_put_snap_context(oldest);
                redirty_page_for_writepage(wbc, page);
                return 0;
        }
        ceph_put_snap_context(oldest);

        /* is this a partial page at end of file? */
        if (page_off >= ceph_wbc.i_size) {
                dout("%p page eof %llu\n", page, ceph_wbc.i_size);
                page->mapping->a_ops->invalidatepage(page, 0, PAGE_SIZE);
                return 0;
        }

        if (ceph_wbc.i_size < page_off + len)
                len = ceph_wbc.i_size - page_off;

        dout("writepage %p page %p index %lu on %llu~%u snapc %p seq %lld\n",
             inode, page, page->index, page_off, len, snapc, snapc->seq);

        if (atomic_long_inc_return(&fsc->writeback_count) >
            CONGESTION_ON_THRESH(fsc->mount_options->congestion_kb))
                set_bdi_congested(inode_to_bdi(inode), BLK_RW_ASYNC);

        set_page_writeback(page);
        err = ceph_sync_writepages(fsc, ceph_vino(inode),
                                   &ci->i_layout, snapc, page_off, len,
                                   ceph_wbc.truncate_seq,
                                   ceph_wbc.truncate_size,
                                   &inode->i_mtime, &page, 1);
        if (err < 0) {
                struct writeback_control tmp_wbc;
                if (!wbc)
                        wbc = &tmp_wbc;
                if (err == -ERESTARTSYS) {
                        /* killed by SIGKILL */
                        dout("writepage interrupted page %p\n", page);
                        redirty_page_for_writepage(wbc, page);
                        end_page_writeback(page);
                        return err;
                }
                if (err == -EBLACKLISTED)
                        fsc->blacklisted = true;
                dout("writepage setting page/mapping error %d %p\n",
                     err, page);
                mapping_set_error(&inode->i_data, err);
                wbc->pages_skipped++;
        } else {
                dout("writepage cleaned page %p\n", page);
                err = 0;  /* vfs expects us to return 0 */
        }
        page->private = 0;
        ClearPagePrivate(page);
        end_page_writeback(page);
        ceph_put_wrbuffer_cap_refs(ci, 1, snapc);
        ceph_put_snap_context(snapc);  /* page's reference */

        if (atomic_long_dec_return(&fsc->writeback_count) <
            CONGESTION_OFF_THRESH(fsc->mount_options->congestion_kb))
                clear_bdi_congested(inode_to_bdi(inode), BLK_RW_ASYNC);

        return err;
}

static int ceph_writepage(struct page *page, struct writeback_control *wbc)
{
        int err;
        struct inode *inode = page->mapping->host;
        BUG_ON(!inode);
        ihold(inode);
        err = writepage_nounlock(page, wbc);
        if (err == -ERESTARTSYS) {
                /* direct memory reclaimer was killed by SIGKILL. return 0
                 * to prevent caller from setting mapping/page error */
                err = 0;
        }
        unlock_page(page);
        iput(inode);
        return err;
}

/*
 * async writeback completion handler.
 *
 * If we get an error, set the mapping error bit, but not the individual
 * page error bits.
 */
static void writepages_finish(struct ceph_osd_request *req)
{
        struct inode *inode = req->r_inode;
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_osd_data *osd_data;
        struct page *page;
        int num_pages, total_pages = 0;
        int i, j;
        int rc = req->r_result;
        struct ceph_snap_context *snapc = req->r_snapc;
        struct address_space *mapping = inode->i_mapping;
        struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
        bool remove_page;

        dout("writepages_finish %p rc %d\n", inode, rc);
        if (rc < 0) {
                mapping_set_error(mapping, rc);
                ceph_set_error_write(ci);
                if (rc == -EBLACKLISTED)
                        fsc->blacklisted = true;
        } else {
                ceph_clear_error_write(ci);
        }

        ceph_update_write_latency(&fsc->mdsc->metric, req->r_start_latency,
                                  req->r_end_latency, rc);

        /*
         * We lost the cache cap, need to truncate the page before
         * it is unlocked, otherwise we'd truncate it later in the
         * page truncation thread, possibly losing some data that
         * raced its way in
         */
        remove_page = !(ceph_caps_issued(ci) &
                        (CEPH_CAP_FILE_CACHE|CEPH_CAP_FILE_LAZYIO));

        /* clean all pages */
        for (i = 0; i < req->r_num_ops; i++) {
                if (req->r_ops[i].op != CEPH_OSD_OP_WRITE)
                        break;

                osd_data = osd_req_op_extent_osd_data(req, i);
                BUG_ON(osd_data->type != CEPH_OSD_DATA_TYPE_PAGES);
                num_pages = calc_pages_for((u64)osd_data->alignment,
                                           (u64)osd_data->length);
                total_pages += num_pages;
                for (j = 0; j < num_pages; j++) {
                        page = osd_data->pages[j];
                        BUG_ON(!page);
                        WARN_ON(!PageUptodate(page));

                        if (atomic_long_dec_return(&fsc->writeback_count) <
                             CONGESTION_OFF_THRESH(
                                        fsc->mount_options->congestion_kb))
                                clear_bdi_congested(inode_to_bdi(inode),
                                                    BLK_RW_ASYNC);

                        ceph_put_snap_context(page_snap_context(page));
                        page->private = 0;
                        ClearPagePrivate(page);
                        dout("unlocking %p\n", page);
                        end_page_writeback(page);

                        if (remove_page)
                                generic_error_remove_page(inode->i_mapping,
                                                          page);

                        unlock_page(page);
                }
                dout("writepages_finish %p wrote %llu bytes cleaned %d pages\n",
                     inode, osd_data->length, rc >= 0 ? num_pages : 0);

                release_pages(osd_data->pages, num_pages);
        }

        ceph_put_wrbuffer_cap_refs(ci, total_pages, snapc);

        osd_data = osd_req_op_extent_osd_data(req, 0);
        if (osd_data->pages_from_pool)
                mempool_free(osd_data->pages, ceph_wb_pagevec_pool);
        else
                kfree(osd_data->pages);
        ceph_osdc_put_request(req);
}

/*
 * initiate async writeback
 */
static int ceph_writepages_start(struct address_space *mapping,
                                 struct writeback_control *wbc)
{
        struct inode *inode = mapping->host;
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
        struct ceph_vino vino = ceph_vino(inode);
        pgoff_t index, start_index, end = -1;
        struct ceph_snap_context *snapc = NULL, *last_snapc = NULL, *pgsnapc;
        struct pagevec pvec;
        int rc = 0;
        unsigned int wsize = i_blocksize(inode);
        struct ceph_osd_request *req = NULL;
        struct ceph_writeback_ctl ceph_wbc;
        bool should_loop, range_whole = false;
        bool done = false;

        dout("writepages_start %p (mode=%s)\n", inode,
             wbc->sync_mode == WB_SYNC_NONE ? "NONE" :
             (wbc->sync_mode == WB_SYNC_ALL ? "ALL" : "HOLD"));

        if (READ_ONCE(fsc->mount_state) == CEPH_MOUNT_SHUTDOWN) {
                if (ci->i_wrbuffer_ref > 0) {
                        pr_warn_ratelimited(
                                "writepage_start %p %lld forced umount\n",
                                inode, ceph_ino(inode));
                }
                mapping_set_error(mapping, -EIO);
                return -EIO; /* we're in a forced umount, don't write! */
        }
        if (fsc->mount_options->wsize < wsize)
                wsize = fsc->mount_options->wsize;

        pagevec_init(&pvec);

        start_index = wbc->range_cyclic ? mapping->writeback_index : 0;
        index = start_index;

retry:
        /* find oldest snap context with dirty data */
        snapc = get_oldest_context(inode, &ceph_wbc, NULL);
        if (!snapc) {
                /* hmm, why does writepages get called when there
                   is no dirty data? */
                dout(" no snap context with dirty data?\n");
                goto out;
        }
        dout(" oldest snapc is %p seq %lld (%d snaps)\n",
             snapc, snapc->seq, snapc->num_snaps);

        should_loop = false;
        if (ceph_wbc.head_snapc && snapc != last_snapc) {
                /* where to start/end? */
                if (wbc->range_cyclic) {
                        index = start_index;
                        end = -1;
                        if (index > 0)
                                should_loop = true;
                        dout(" cyclic, start at %lu\n", index);
                } else {
                        index = wbc->range_start >> PAGE_SHIFT;
                        end = wbc->range_end >> PAGE_SHIFT;
                        if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)
                                range_whole = true;
                        dout(" not cyclic, %lu to %lu\n", index, end);
                }
        } else if (!ceph_wbc.head_snapc) {
                /* Do not respect wbc->range_{start,end}. Dirty pages
                 * in that range can be associated with newer snapc.
                 * They are not writeable until we write all dirty pages
                 * associated with 'snapc' get written */
                if (index > 0)
                        should_loop = true;
                dout(" non-head snapc, range whole\n");
        }

        ceph_put_snap_context(last_snapc);
        last_snapc = snapc;

        while (!done && index <= end) {
                int num_ops = 0, op_idx;
                unsigned i, pvec_pages, max_pages, locked_pages = 0;
                struct page **pages = NULL, **data_pages;
                struct page *page;
                pgoff_t strip_unit_end = 0;
                u64 offset = 0, len = 0;
                bool from_pool = false;

                max_pages = wsize >> PAGE_SHIFT;

get_more_pages:
                pvec_pages = pagevec_lookup_range_nr_tag(&pvec, mapping, &index,
                                                end, PAGECACHE_TAG_DIRTY,
                                                max_pages - locked_pages);
                dout("pagevec_lookup_range_tag got %d\n", pvec_pages);
                if (!pvec_pages && !locked_pages)
                        break;
                for (i = 0; i < pvec_pages && locked_pages < max_pages; i++) {
                        page = pvec.pages[i];
                        dout("? %p idx %lu\n", page, page->index);
                        if (locked_pages == 0)
                                lock_page(page);  /* first page */
                        else if (!trylock_page(page))
                                break;

                        /* only dirty pages, or our accounting breaks */
                        if (unlikely(!PageDirty(page)) ||
                            unlikely(page->mapping != mapping)) {
                                dout("!dirty or !mapping %p\n", page);
                                unlock_page(page);
                                continue;
                        }
                        /* only if matching snap context */
                        pgsnapc = page_snap_context(page);
                        if (pgsnapc != snapc) {
                                dout("page snapc %p %lld != oldest %p %lld\n",
                                     pgsnapc, pgsnapc->seq, snapc, snapc->seq);
                                if (!should_loop &&
                                    !ceph_wbc.head_snapc &&
                                    wbc->sync_mode != WB_SYNC_NONE)
                                        should_loop = true;
                                unlock_page(page);
                                continue;
                        }
                        if (page_offset(page) >= ceph_wbc.i_size) {
                                dout("%p page eof %llu\n",
                                     page, ceph_wbc.i_size);

                                if ((ceph_wbc.size_stable ||
                                    page_offset(page) >= i_size_read(inode)) &&
                                    clear_page_dirty_for_io(page))
                                        mapping->a_ops->invalidatepage(page,
                                                                0, PAGE_SIZE);
                                unlock_page(page);
                                continue;
                        }
                        if (strip_unit_end && (page->index > strip_unit_end)) {
                                dout("end of strip unit %p\n", page);
                                unlock_page(page);
                                break;
                        }
                        if (PageWriteback(page)) {
                                if (wbc->sync_mode == WB_SYNC_NONE) {
                                        dout("%p under writeback\n", page);
                                        unlock_page(page);
                                        continue;
                                }
                                dout("waiting on writeback %p\n", page);
                                wait_on_page_writeback(page);
                        }

                        if (!clear_page_dirty_for_io(page)) {
                                dout("%p !clear_page_dirty_for_io\n", page);
                                unlock_page(page);
                                continue;
                        }

                        /*
                         * We have something to write.  If this is
                         * the first locked page this time through,
                         * calculate max possinle write size and
                         * allocate a page array
                         */
                        if (locked_pages == 0) {
                                u64 objnum;
                                u64 objoff;
                                u32 xlen;

                                /* prepare async write request */
                                offset = (u64)page_offset(page);
                                ceph_calc_file_object_mapping(&ci->i_layout,
                                                              offset, wsize,
                                                              &objnum, &objoff,
                                                              &xlen);
                                len = xlen;

                                num_ops = 1;
                                strip_unit_end = page->index +
                                        ((len - 1) >> PAGE_SHIFT);

                                BUG_ON(pages);
                                max_pages = calc_pages_for(0, (u64)len);
                                pages = kmalloc_array(max_pages,
                                                      sizeof(*pages),
                                                      GFP_NOFS);
                                if (!pages) {
                                        from_pool = true;
                                        pages = mempool_alloc(ceph_wb_pagevec_pool, GFP_NOFS);
                                        BUG_ON(!pages);
                                }

                                len = 0;
                        } else if (page->index !=
                                   (offset + len) >> PAGE_SHIFT) {
                                if (num_ops >= (from_pool ?  CEPH_OSD_SLAB_OPS :
                                                             CEPH_OSD_MAX_OPS)) {
                                        redirty_page_for_writepage(wbc, page);
                                        unlock_page(page);
                                        break;
                                }

                                num_ops++;
                                offset = (u64)page_offset(page);
                                len = 0;
                        }

                        /* note position of first page in pvec */
                        dout("%p will write page %p idx %lu\n",
                             inode, page, page->index);

                        if (atomic_long_inc_return(&fsc->writeback_count) >
                            CONGESTION_ON_THRESH(
                                    fsc->mount_options->congestion_kb)) {
                                set_bdi_congested(inode_to_bdi(inode),
                                                  BLK_RW_ASYNC);
                        }


                        pages[locked_pages++] = page;
                        pvec.pages[i] = NULL;

                        len += PAGE_SIZE;
                }

                /* did we get anything? */
                if (!locked_pages)
                        goto release_pvec_pages;
                if (i) {
                        unsigned j, n = 0;
                        /* shift unused page to beginning of pvec */
                        for (j = 0; j < pvec_pages; j++) {
                                if (!pvec.pages[j])
                                        continue;
                                if (n < j)
                                        pvec.pages[n] = pvec.pages[j];
                                n++;
                        }
                        pvec.nr = n;

                        if (pvec_pages && i == pvec_pages &&
                            locked_pages < max_pages) {
                                dout("reached end pvec, trying for more\n");
                                pagevec_release(&pvec);
                                goto get_more_pages;
                        }
                }

new_request:
                offset = page_offset(pages[0]);
                len = wsize;

                req = ceph_osdc_new_request(&fsc->client->osdc,
                                        &ci->i_layout, vino,
                                        offset, &len, 0, num_ops,
                                        CEPH_OSD_OP_WRITE, CEPH_OSD_FLAG_WRITE,
                                        snapc, ceph_wbc.truncate_seq,
                                        ceph_wbc.truncate_size, false);
                if (IS_ERR(req)) {
                        req = ceph_osdc_new_request(&fsc->client->osdc,
                                                &ci->i_layout, vino,
                                                offset, &len, 0,
                                                min(num_ops,
                                                    CEPH_OSD_SLAB_OPS),
                                                CEPH_OSD_OP_WRITE,
                                                CEPH_OSD_FLAG_WRITE,
                                                snapc, ceph_wbc.truncate_seq,
                                                ceph_wbc.truncate_size, true);
                        BUG_ON(IS_ERR(req));
                }
                BUG_ON(len < page_offset(pages[locked_pages - 1]) +
                             PAGE_SIZE - offset);

                req->r_callback = writepages_finish;
                req->r_inode = inode;

                /* Format the osd request message and submit the write */
                len = 0;
                data_pages = pages;
                op_idx = 0;
                for (i = 0; i < locked_pages; i++) {
                        u64 cur_offset = page_offset(pages[i]);
                        if (offset + len != cur_offset) {
                                if (op_idx + 1 == req->r_num_ops)
                                        break;
                                osd_req_op_extent_dup_last(req, op_idx,
                                                           cur_offset - offset);
                                dout("writepages got pages at %llu~%llu\n",
                                     offset, len);
                                osd_req_op_extent_osd_data_pages(req, op_idx,
                                                        data_pages, len, 0,
                                                        from_pool, false);
                                osd_req_op_extent_update(req, op_idx, len);

                                len = 0;
                                offset = cur_offset; 
                                data_pages = pages + i;
                                op_idx++;
                        }

                        set_page_writeback(pages[i]);
                        len += PAGE_SIZE;
                }

                if (ceph_wbc.size_stable) {
                        len = min(len, ceph_wbc.i_size - offset);
                } else if (i == locked_pages) {
                        /* writepages_finish() clears writeback pages
                         * according to the data length, so make sure
                         * data length covers all locked pages */
                        u64 min_len = len + 1 - PAGE_SIZE;
                        len = get_writepages_data_length(inode, pages[i - 1],
                                                         offset);
                        len = max(len, min_len);
                }
                dout("writepages got pages at %llu~%llu\n", offset, len);

                osd_req_op_extent_osd_data_pages(req, op_idx, data_pages, len,
                                                 0, from_pool, false);
                osd_req_op_extent_update(req, op_idx, len);

                BUG_ON(op_idx + 1 != req->r_num_ops);

                from_pool = false;
                if (i < locked_pages) {
                        BUG_ON(num_ops <= req->r_num_ops);
                        num_ops -= req->r_num_ops;
                        locked_pages -= i;

                        /* allocate new pages array for next request */
                        data_pages = pages;
                        pages = kmalloc_array(locked_pages, sizeof(*pages),
                                              GFP_NOFS);
                        if (!pages) {
                                from_pool = true;
                                pages = mempool_alloc(ceph_wb_pagevec_pool, GFP_NOFS);
                                BUG_ON(!pages);
                        }
                        memcpy(pages, data_pages + i,
                               locked_pages * sizeof(*pages));
                        memset(data_pages + i, 0,
                               locked_pages * sizeof(*pages));
                } else {
                        BUG_ON(num_ops != req->r_num_ops);
                        index = pages[i - 1]->index + 1;
                        /* request message now owns the pages array */
                        pages = NULL;
                }

                req->r_mtime = inode->i_mtime;
                rc = ceph_osdc_start_request(&fsc->client->osdc, req, true);
                BUG_ON(rc);
                req = NULL;

                wbc->nr_to_write -= i;
                if (pages)
                        goto new_request;

                /*
                 * We stop writing back only if we are not doing
                 * integrity sync. In case of integrity sync we have to
                 * keep going until we have written all the pages
                 * we tagged for writeback prior to entering this loop.
                 */
                if (wbc->nr_to_write <= 0 && wbc->sync_mode == WB_SYNC_NONE)
                        done = true;

release_pvec_pages:
                dout("pagevec_release on %d pages (%p)\n", (int)pvec.nr,
                     pvec.nr ? pvec.pages[0] : NULL);
                pagevec_release(&pvec);
        }

        if (should_loop && !done) {
                /* more to do; loop back to beginning of file */
                dout("writepages looping back to beginning of file\n");
                end = start_index - 1; /* OK even when start_index == 0 */

                /* to write dirty pages associated with next snapc,
                 * we need to wait until current writes complete */
                if (wbc->sync_mode != WB_SYNC_NONE &&
                    start_index == 0 && /* all dirty pages were checked */
                    !ceph_wbc.head_snapc) {
                        struct page *page;
                        unsigned i, nr;
                        index = 0;
                        while ((index <= end) &&
                               (nr = pagevec_lookup_tag(&pvec, mapping, &index,
                                                PAGECACHE_TAG_WRITEBACK))) {
                                for (i = 0; i < nr; i++) {
                                        page = pvec.pages[i];
                                        if (page_snap_context(page) != snapc)
                                                continue;
                                        wait_on_page_writeback(page);
                                }
                                pagevec_release(&pvec);
                                cond_resched();
                        }
                }

                start_index = 0;
                index = 0;
                goto retry;
        }

        if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
                mapping->writeback_index = index;

out:
        ceph_osdc_put_request(req);
        ceph_put_snap_context(last_snapc);
        dout("writepages dend - startone, rc = %d\n", rc);
        return rc;
}



/*
 * See if a given @snapc is either writeable, or already written.
 */
static int context_is_writeable_or_written(struct inode *inode,
                                           struct ceph_snap_context *snapc)
{
        struct ceph_snap_context *oldest = get_oldest_context(inode, NULL, NULL);
        int ret = !oldest || snapc->seq <= oldest->seq;

        ceph_put_snap_context(oldest);
        return ret;
}

/*
 * We are only allowed to write into/dirty the page if the page is
 * clean, or already dirty within the same snap context.
 *
 * called with page locked.
 * return success with page locked,
 * or any failure (incl -EAGAIN) with page unlocked.
 */
static int ceph_update_writeable_page(struct file *file,
                            loff_t pos, unsigned len,
                            struct page *page)
{
        struct inode *inode = file_inode(file);
        struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
        struct ceph_inode_info *ci = ceph_inode(inode);
        loff_t page_off = pos & PAGE_MASK;
        int pos_in_page = pos & ~PAGE_MASK;
        int end_in_page = pos_in_page + len;
        loff_t i_size;
        int r;
        struct ceph_snap_context *snapc, *oldest;

        if (READ_ONCE(fsc->mount_state) == CEPH_MOUNT_SHUTDOWN) {
                dout(" page %p forced umount\n", page);
                unlock_page(page);
                return -EIO;
        }

retry_locked:
        /* writepages currently holds page lock, but if we change that later, */
        wait_on_page_writeback(page);

        snapc = page_snap_context(page);
        if (snapc && snapc != ci->i_head_snapc) {
                /*
                 * this page is already dirty in another (older) snap
                 * context!  is it writeable now?
                 */
                oldest = get_oldest_context(inode, NULL, NULL);
                if (snapc->seq > oldest->seq) {
                        ceph_put_snap_context(oldest);
                        dout(" page %p snapc %p not current or oldest\n",
                             page, snapc);
                        /*
                         * queue for writeback, and wait for snapc to
                         * be writeable or written
                         */
                        snapc = ceph_get_snap_context(snapc);
                        unlock_page(page);
                        ceph_queue_writeback(inode);
                        r = wait_event_killable(ci->i_cap_wq,
                               context_is_writeable_or_written(inode, snapc));
                        ceph_put_snap_context(snapc);
                        if (r == -ERESTARTSYS)
                                return r;
                        return -EAGAIN;
                }
                ceph_put_snap_context(oldest);

                /* yay, writeable, do it now (without dropping page lock) */
                dout(" page %p snapc %p not current, but oldest\n",
                     page, snapc);
                if (!clear_page_dirty_for_io(page))
                        goto retry_locked;
                r = writepage_nounlock(page, NULL);
                if (r < 0)
                        goto fail_unlock;
                goto retry_locked;
        }

        if (PageUptodate(page)) {
                dout(" page %p already uptodate\n", page);
                return 0;
        }

        /* full page? */
        if (pos_in_page == 0 && len == PAGE_SIZE)
                return 0;

        /* past end of file? */
        i_size = i_size_read(inode);

        if (page_off >= i_size ||
            (pos_in_page == 0 && (pos+len) >= i_size &&
             end_in_page - pos_in_page != PAGE_SIZE)) {
                dout(" zeroing %p 0 - %d and %d - %d\n",
                     page, pos_in_page, end_in_page, (int)PAGE_SIZE);
                zero_user_segments(page,
                                   0, pos_in_page,
                                   end_in_page, PAGE_SIZE);
                return 0;
        }

        /* we need to read it. */
        r = ceph_do_readpage(file, page);
        if (r < 0) {
                if (r == -EINPROGRESS)
                        return -EAGAIN;
                goto fail_unlock;
        }
        goto retry_locked;
fail_unlock:
        unlock_page(page);
        return r;
}

/*
 * We are only allowed to write into/dirty the page if the page is
 * clean, or already dirty within the same snap context.
 */
static int ceph_write_begin(struct file *file, struct address_space *mapping,
                            loff_t pos, unsigned len, unsigned flags,
                            struct page **pagep, void **fsdata)
{
        struct inode *inode = file_inode(file);
        struct page *page;
        pgoff_t index = pos >> PAGE_SHIFT;
        int r;

        do {
                /* get a page */
                page = grab_cache_page_write_begin(mapping, index, 0);
                if (!page)
                        return -ENOMEM;

                dout("write_begin file %p inode %p page %p %d~%d\n", file,
                     inode, page, (int)pos, (int)len);

                r = ceph_update_writeable_page(file, pos, len, page);
                if (r < 0)
                        put_page(page);
                else
                        *pagep = page;
        } while (r == -EAGAIN);

        return r;
}

/*
 * we don't do anything in here that simple_write_end doesn't do
 * except adjust dirty page accounting
 */
static int ceph_write_end(struct file *file, struct address_space *mapping,
                          loff_t pos, unsigned len, unsigned copied,
                          struct page *page, void *fsdata)
{
        struct inode *inode = file_inode(file);
        bool check_cap = false;

        dout("write_end file %p inode %p page %p %d~%d (%d)\n", file,
             inode, page, (int)pos, (int)copied, (int)len);

        /* zero the stale part of the page if we did a short copy */
        if (!PageUptodate(page)) {
                if (copied < len) {
                        copied = 0;
                        goto out;
                }
                SetPageUptodate(page);
        }

        /* did file size increase? */
        if (pos+copied > i_size_read(inode))
                check_cap = ceph_inode_set_size(inode, pos+copied);

        set_page_dirty(page);

out:
        unlock_page(page);
        put_page(page);

        if (check_cap)
                ceph_check_caps(ceph_inode(inode), CHECK_CAPS_AUTHONLY, NULL);

        return copied;
}

/*
 * we set .direct_IO to indicate direct io is supported, but since we
 * intercept O_DIRECT reads and writes early, this function should
 * never get called.
 */
static ssize_t ceph_direct_io(struct kiocb *iocb, struct iov_iter *iter)
{
        WARN_ON(1);
        return -EINVAL;
}

const struct address_space_operations ceph_aops = {
        .readpage = ceph_readpage,
        .readpages = ceph_readpages,
        .writepage = ceph_writepage,
        .writepages = ceph_writepages_start,
        .write_begin = ceph_write_begin,
        .write_end = ceph_write_end,
        .set_page_dirty = ceph_set_page_dirty,
        .invalidatepage = ceph_invalidatepage,
        .releasepage = ceph_releasepage,
        .direct_IO = ceph_direct_io,
};

static void ceph_block_sigs(sigset_t *oldset)
{
        sigset_t mask;
        siginitsetinv(&mask, sigmask(SIGKILL));
        sigprocmask(SIG_BLOCK, &mask, oldset);
}

static void ceph_restore_sigs(sigset_t *oldset)
{
        sigprocmask(SIG_SETMASK, oldset, NULL);
}

/*
 * vm ops
 */
static vm_fault_t ceph_filemap_fault(struct vm_fault *vmf)
{
        struct vm_area_struct *vma = vmf->vma;
        struct inode *inode = file_inode(vma->vm_file);
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_file_info *fi = vma->vm_file->private_data;
        struct page *pinned_page = NULL;
        loff_t off = vmf->pgoff << PAGE_SHIFT;
        int want, got, err;
        sigset_t oldset;
        vm_fault_t ret = VM_FAULT_SIGBUS;

        ceph_block_sigs(&oldset);

        dout("filemap_fault %p %llx.%llx %llu~%zd trying to get caps\n",
             inode, ceph_vinop(inode), off, (size_t)PAGE_SIZE);
        if (fi->fmode & CEPH_FILE_MODE_LAZY)
                want = CEPH_CAP_FILE_CACHE | CEPH_CAP_FILE_LAZYIO;
        else
                want = CEPH_CAP_FILE_CACHE;

        got = 0;
        err = ceph_get_caps(vma->vm_file, CEPH_CAP_FILE_RD, want, -1,
                            &got, &pinned_page);
        if (err < 0)
                goto out_restore;

        dout("filemap_fault %p %llu~%zd got cap refs on %s\n",
             inode, off, (size_t)PAGE_SIZE, ceph_cap_string(got));

        if ((got & (CEPH_CAP_FILE_CACHE | CEPH_CAP_FILE_LAZYIO)) ||
            ci->i_inline_version == CEPH_INLINE_NONE) {
                CEPH_DEFINE_RW_CONTEXT(rw_ctx, got);
                ceph_add_rw_context(fi, &rw_ctx);
                ret = filemap_fault(vmf);
                ceph_del_rw_context(fi, &rw_ctx);
                dout("filemap_fault %p %llu~%zd drop cap refs %s ret %x\n",
                        inode, off, (size_t)PAGE_SIZE,
                                ceph_cap_string(got), ret);
        } else
                err = -EAGAIN;

        if (pinned_page)
                put_page(pinned_page);
        ceph_put_cap_refs(ci, got);

        if (err != -EAGAIN)
                goto out_restore;

        /* read inline data */
        if (off >= PAGE_SIZE) {
                /* does not support inline data > PAGE_SIZE */
                ret = VM_FAULT_SIGBUS;
        } else {
                struct address_space *mapping = inode->i_mapping;
                struct page *page = find_or_create_page(mapping, 0,
                                                mapping_gfp_constraint(mapping,
                                                ~__GFP_FS));
                if (!page) {
                        ret = VM_FAULT_OOM;
                        goto out_inline;
                }
                err = __ceph_do_getattr(inode, page,
                                         CEPH_STAT_CAP_INLINE_DATA, true);
                if (err < 0 || off >= i_size_read(inode)) {
                        unlock_page(page);
                        put_page(page);
                        ret = vmf_error(err);
                        goto out_inline;
                }
                if (err < PAGE_SIZE)
                        zero_user_segment(page, err, PAGE_SIZE);
                else
                        flush_dcache_page(page);
                SetPageUptodate(page);
                vmf->page = page;
                ret = VM_FAULT_MAJOR | VM_FAULT_LOCKED;
out_inline:
                dout("filemap_fault %p %llu~%zd read inline data ret %x\n",
                     inode, off, (size_t)PAGE_SIZE, ret);
        }
out_restore:
        ceph_restore_sigs(&oldset);
        if (err < 0)
                ret = vmf_error(err);

        return ret;
}

/*
 * Reuse write_begin here for simplicity.
 */
static vm_fault_t ceph_page_mkwrite(struct vm_fault *vmf)
{
        struct vm_area_struct *vma = vmf->vma;
        struct inode *inode = file_inode(vma->vm_file);
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_file_info *fi = vma->vm_file->private_data;
        struct ceph_cap_flush *prealloc_cf;
        struct page *page = vmf->page;
        loff_t off = page_offset(page);
        loff_t size = i_size_read(inode);
        size_t len;
        int want, got, err;
        sigset_t oldset;
        vm_fault_t ret = VM_FAULT_SIGBUS;

        prealloc_cf = ceph_alloc_cap_flush();
        if (!prealloc_cf)
                return VM_FAULT_OOM;

        sb_start_pagefault(inode->i_sb);
        ceph_block_sigs(&oldset);

        if (ci->i_inline_version != CEPH_INLINE_NONE) {
                struct page *locked_page = NULL;
                if (off == 0) {
                        lock_page(page);
                        locked_page = page;
                }
                err = ceph_uninline_data(vma->vm_file, locked_page);
                if (locked_page)
                        unlock_page(locked_page);
                if (err < 0)
                        goto out_free;
        }

        if (off + PAGE_SIZE <= size)
                len = PAGE_SIZE;
        else
                len = size & ~PAGE_MASK;

        dout("page_mkwrite %p %llx.%llx %llu~%zd getting caps i_size %llu\n",
             inode, ceph_vinop(inode), off, len, size);
        if (fi->fmode & CEPH_FILE_MODE_LAZY)
                want = CEPH_CAP_FILE_BUFFER | CEPH_CAP_FILE_LAZYIO;
        else
                want = CEPH_CAP_FILE_BUFFER;

        got = 0;
        err = ceph_get_caps(vma->vm_file, CEPH_CAP_FILE_WR, want, off + len,
                            &got, NULL);
        if (err < 0)
                goto out_free;

        dout("page_mkwrite %p %llu~%zd got cap refs on %s\n",
             inode, off, len, ceph_cap_string(got));

        /* Update time before taking page lock */
        file_update_time(vma->vm_file);
        inode_inc_iversion_raw(inode);

        do {
                lock_page(page);

                if (page_mkwrite_check_truncate(page, inode) < 0) {
                        unlock_page(page);
                        ret = VM_FAULT_NOPAGE;
                        break;
                }

                err = ceph_update_writeable_page(vma->vm_file, off, len, page);
                if (err >= 0) {
                        /* success.  we'll keep the page locked. */
                        set_page_dirty(page);
                        ret = VM_FAULT_LOCKED;
                }
        } while (err == -EAGAIN);

        if (ret == VM_FAULT_LOCKED ||
            ci->i_inline_version != CEPH_INLINE_NONE) {
                int dirty;
                spin_lock(&ci->i_ceph_lock);
                ci->i_inline_version = CEPH_INLINE_NONE;
                dirty = __ceph_mark_dirty_caps(ci, CEPH_CAP_FILE_WR,
                                               &prealloc_cf);
                spin_unlock(&ci->i_ceph_lock);
                if (dirty)
                        __mark_inode_dirty(inode, dirty);
        }

        dout("page_mkwrite %p %llu~%zd dropping cap refs on %s ret %x\n",
             inode, off, len, ceph_cap_string(got), ret);
        ceph_put_cap_refs(ci, got);
out_free:
        ceph_restore_sigs(&oldset);
        sb_end_pagefault(inode->i_sb);
        ceph_free_cap_flush(prealloc_cf);
        if (err < 0)
                ret = vmf_error(err);
        return ret;
}

void ceph_fill_inline_data(struct inode *inode, struct page *locked_page,
                           char *data, size_t len)
{
        struct address_space *mapping = inode->i_mapping;
        struct page *page;

        if (locked_page) {
                page = locked_page;
        } else {
                if (i_size_read(inode) == 0)
                        return;
                page = find_or_create_page(mapping, 0,
                                           mapping_gfp_constraint(mapping,
                                           ~__GFP_FS));
                if (!page)
                        return;
                if (PageUptodate(page)) {
                        unlock_page(page);
                        put_page(page);
                        return;
                }
        }

        dout("fill_inline_data %p %llx.%llx len %zu locked_page %p\n",
             inode, ceph_vinop(inode), len, locked_page);

        if (len > 0) {
                void *kaddr = kmap_atomic(page);
                memcpy(kaddr, data, len);
                kunmap_atomic(kaddr);
        }

        if (page != locked_page) {
                if (len < PAGE_SIZE)
                        zero_user_segment(page, len, PAGE_SIZE);
                else
                        flush_dcache_page(page);

                SetPageUptodate(page);
                unlock_page(page);
                put_page(page);
        }
}

int ceph_uninline_data(struct file *filp, struct page *locked_page)
{
        struct inode *inode = file_inode(filp);
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_fs_client *fsc = ceph_inode_to_client(inode);
        struct ceph_osd_request *req;
        struct page *page = NULL;
        u64 len, inline_version;
        int err = 0;
        bool from_pagecache = false;

        spin_lock(&ci->i_ceph_lock);
        inline_version = ci->i_inline_version;
        spin_unlock(&ci->i_ceph_lock);

        dout("uninline_data %p %llx.%llx inline_version %llu\n",
             inode, ceph_vinop(inode), inline_version);

        if (inline_version == 1 || /* initial version, no data */
            inline_version == CEPH_INLINE_NONE)
                goto out;

        if (locked_page) {
                page = locked_page;
                WARN_ON(!PageUptodate(page));
        } else if (ceph_caps_issued(ci) &
                   (CEPH_CAP_FILE_CACHE|CEPH_CAP_FILE_LAZYIO)) {
                page = find_get_page(inode->i_mapping, 0);
                if (page) {
                        if (PageUptodate(page)) {
                                from_pagecache = true;
                                lock_page(page);
                        } else {
                                put_page(page);
                                page = NULL;
                        }
                }
        }

        if (page) {
                len = i_size_read(inode);
                if (len > PAGE_SIZE)
                        len = PAGE_SIZE;
        } else {
                page = __page_cache_alloc(GFP_NOFS);
                if (!page) {
                        err = -ENOMEM;
                        goto out;
                }
                err = __ceph_do_getattr(inode, page,
                                        CEPH_STAT_CAP_INLINE_DATA, true);
                if (err < 0) {
                        /* no inline data */
                        if (err == -ENODATA)
                                err = 0;
                        goto out;
                }
                len = err;
        }

        req = ceph_osdc_new_request(&fsc->client->osdc, &ci->i_layout,
                                    ceph_vino(inode), 0, &len, 0, 1,
                                    CEPH_OSD_OP_CREATE, CEPH_OSD_FLAG_WRITE,
                                    NULL, 0, 0, false);
        if (IS_ERR(req)) {
                err = PTR_ERR(req);
                goto out;
        }

        req->r_mtime = inode->i_mtime;
        err = ceph_osdc_start_request(&fsc->client->osdc, req, false);
        if (!err)
                err = ceph_osdc_wait_request(&fsc->client->osdc, req);
        ceph_osdc_put_request(req);
        if (err < 0)
                goto out;

        req = ceph_osdc_new_request(&fsc->client->osdc, &ci->i_layout,
                                    ceph_vino(inode), 0, &len, 1, 3,
                                    CEPH_OSD_OP_WRITE, CEPH_OSD_FLAG_WRITE,
                                    NULL, ci->i_truncate_seq,
                                    ci->i_truncate_size, false);
        if (IS_ERR(req)) {
                err = PTR_ERR(req);
                goto out;
        }

        osd_req_op_extent_osd_data_pages(req, 1, &page, len, 0, false, false);

        {
                __le64 xattr_buf = cpu_to_le64(inline_version);
                err = osd_req_op_xattr_init(req, 0, CEPH_OSD_OP_CMPXATTR,
                                            "inline_version", &xattr_buf,
                                            sizeof(xattr_buf),
                                            CEPH_OSD_CMPXATTR_OP_GT,
                                            CEPH_OSD_CMPXATTR_MODE_U64);
                if (err)
                        goto out_put;
        }

        {
                char xattr_buf[32];
                int xattr_len = snprintf(xattr_buf, sizeof(xattr_buf),
                                         "%llu", inline_version);
                err = osd_req_op_xattr_init(req, 2, CEPH_OSD_OP_SETXATTR,
                                            "inline_version",
                                            xattr_buf, xattr_len, 0, 0);
                if (err)
                        goto out_put;
        }

        req->r_mtime = inode->i_mtime;
        err = ceph_osdc_start_request(&fsc->client->osdc, req, false);
        if (!err)
                err = ceph_osdc_wait_request(&fsc->client->osdc, req);

        ceph_update_write_latency(&fsc->mdsc->metric, req->r_start_latency,
                                  req->r_end_latency, err);

out_put:
        ceph_osdc_put_request(req);
        if (err == -ECANCELED)
                err = 0;
out:
        if (page && page != locked_page) {
                if (from_pagecache) {
                        unlock_page(page);
                        put_page(page);
                } else
                        __free_pages(page, 0);
        }

        dout("uninline_data %p %llx.%llx inline_version %llu = %d\n",
             inode, ceph_vinop(inode), inline_version, err);
        return err;
}

static const struct vm_operations_struct ceph_vmops = {
        .fault          = ceph_filemap_fault,
        .page_mkwrite   = ceph_page_mkwrite,
};

int ceph_mmap(struct file *file, struct vm_area_struct *vma)
{
        struct address_space *mapping = file->f_mapping;

        if (!mapping->a_ops->readpage)
                return -ENOEXEC;
        file_accessed(file);
        vma->vm_ops = &ceph_vmops;
        return 0;
}

enum {
        POOL_READ       = 1,
        POOL_WRITE      = 2,
};

static int __ceph_pool_perm_get(struct ceph_inode_info *ci,
                                s64 pool, struct ceph_string *pool_ns)
{
        struct ceph_fs_client *fsc = ceph_inode_to_client(&ci->vfs_inode);
        struct ceph_mds_client *mdsc = fsc->mdsc;
        struct ceph_osd_request *rd_req = NULL, *wr_req = NULL;
        struct rb_node **p, *parent;
        struct ceph_pool_perm *perm;
        struct page **pages;
        size_t pool_ns_len;
        int err = 0, err2 = 0, have = 0;

        down_read(&mdsc->pool_perm_rwsem);
        p = &mdsc->pool_perm_tree.rb_node;
        while (*p) {
                perm = rb_entry(*p, struct ceph_pool_perm, node);
                if (pool < perm->pool)
                        p = &(*p)->rb_left;
                else if (pool > perm->pool)
                        p = &(*p)->rb_right;
                else {
                        int ret = ceph_compare_string(pool_ns,
                                                perm->pool_ns,
                                                perm->pool_ns_len);
                        if (ret < 0)
                                p = &(*p)->rb_left;
                        else if (ret > 0)
                                p = &(*p)->rb_right;
                        else {
                                have = perm->perm;
                                break;
                        }
                }
        }
        up_read(&mdsc->pool_perm_rwsem);
        if (*p)
                goto out;

        if (pool_ns)
                dout("__ceph_pool_perm_get pool %lld ns %.*s no perm cached\n",
                     pool, (int)pool_ns->len, pool_ns->str);
        else
                dout("__ceph_pool_perm_get pool %lld no perm cached\n", pool);

        down_write(&mdsc->pool_perm_rwsem);
        p = &mdsc->pool_perm_tree.rb_node;
        parent = NULL;
        while (*p) {
                parent = *p;
                perm = rb_entry(parent, struct ceph_pool_perm, node);
                if (pool < perm->pool)
                        p = &(*p)->rb_left;
                else if (pool > perm->pool)
                        p = &(*p)->rb_right;
                else {
                        int ret = ceph_compare_string(pool_ns,
                                                perm->pool_ns,
                                                perm->pool_ns_len);
                        if (ret < 0)
                                p = &(*p)->rb_left;
                        else if (ret > 0)
                                p = &(*p)->rb_right;
                        else {
                                have = perm->perm;
                                break;
                        }
                }
        }
        if (*p) {
                up_write(&mdsc->pool_perm_rwsem);
                goto out;
        }

        rd_req = ceph_osdc_alloc_request(&fsc->client->osdc, NULL,
                                         1, false, GFP_NOFS);
        if (!rd_req) {
                err = -ENOMEM;
                goto out_unlock;
        }

        rd_req->r_flags = CEPH_OSD_FLAG_READ;
        osd_req_op_init(rd_req, 0, CEPH_OSD_OP_STAT, 0);
        rd_req->r_base_oloc.pool = pool;
        if (pool_ns)
                rd_req->r_base_oloc.pool_ns = ceph_get_string(pool_ns);
        ceph_oid_printf(&rd_req->r_base_oid, "%llx.00000000", ci->i_vino.ino);

        err = ceph_osdc_alloc_messages(rd_req, GFP_NOFS);

        if (err)
                goto out_unlock;

        wr_req = ceph_osdc_alloc_request(&fsc->client->osdc, NULL,
                                         1, false, GFP_NOFS);
        if (!wr_req) {
                err = -ENOMEM;
                goto out_unlock;
        }

        wr_req->r_flags = CEPH_OSD_FLAG_WRITE;
        osd_req_op_init(wr_req, 0, CEPH_OSD_OP_CREATE, CEPH_OSD_OP_FLAG_EXCL);
        ceph_oloc_copy(&wr_req->r_base_oloc, &rd_req->r_base_oloc);
        ceph_oid_copy(&wr_req->r_base_oid, &rd_req->r_base_oid);

        err = ceph_osdc_alloc_messages(wr_req, GFP_NOFS);
        if (err)
                goto out_unlock;

        /* one page should be large enough for STAT data */
        pages = ceph_alloc_page_vector(1, GFP_KERNEL);
        if (IS_ERR(pages)) {
                err = PTR_ERR(pages);
                goto out_unlock;
        }

        osd_req_op_raw_data_in_pages(rd_req, 0, pages, PAGE_SIZE,
                                     0, false, true);
        err = ceph_osdc_start_request(&fsc->client->osdc, rd_req, false);

        wr_req->r_mtime = ci->vfs_inode.i_mtime;
        err2 = ceph_osdc_start_request(&fsc->client->osdc, wr_req, false);

        if (!err)
                err = ceph_osdc_wait_request(&fsc->client->osdc, rd_req);
        if (!err2)
                err2 = ceph_osdc_wait_request(&fsc->client->osdc, wr_req);

        if (err >= 0 || err == -ENOENT)
                have |= POOL_READ;
        else if (err != -EPERM) {
                if (err == -EBLACKLISTED)
                        fsc->blacklisted = true;
                goto out_unlock;
        }

        if (err2 == 0 || err2 == -EEXIST)
                have |= POOL_WRITE;
        else if (err2 != -EPERM) {
                if (err2 == -EBLACKLISTED)
                        fsc->blacklisted = true;
                err = err2;
                goto out_unlock;
        }

        pool_ns_len = pool_ns ? pool_ns->len : 0;
        perm = kmalloc(sizeof(*perm) + pool_ns_len + 1, GFP_NOFS);
        if (!perm) {
                err = -ENOMEM;
                goto out_unlock;
        }

        perm->pool = pool;
        perm->perm = have;
        perm->pool_ns_len = pool_ns_len;
        if (pool_ns_len > 0)
                memcpy(perm->pool_ns, pool_ns->str, pool_ns_len);
        perm->pool_ns[pool_ns_len] = 0;

        rb_link_node(&perm->node, parent, p);
        rb_insert_color(&perm->node, &mdsc->pool_perm_tree);
        err = 0;
out_unlock:
        up_write(&mdsc->pool_perm_rwsem);

        ceph_osdc_put_request(rd_req);
        ceph_osdc_put_request(wr_req);
out:
        if (!err)
                err = have;
        if (pool_ns)
                dout("__ceph_pool_perm_get pool %lld ns %.*s result = %d\n",
                     pool, (int)pool_ns->len, pool_ns->str, err);
        else
                dout("__ceph_pool_perm_get pool %lld result = %d\n", pool, err);
        return err;
}

int ceph_pool_perm_check(struct inode *inode, int need)
{
        struct ceph_inode_info *ci = ceph_inode(inode);
        struct ceph_string *pool_ns;
        s64 pool;
        int ret, flags;

        if (ci->i_vino.snap != CEPH_NOSNAP) {
                /*
                 * Pool permission check needs to write to the first object.
                 * But for snapshot, head of the first object may have alread
                 * been deleted. Skip check to avoid creating orphan object.
                 */
                return 0;
        }

        if (ceph_test_mount_opt(ceph_inode_to_client(inode),
                                NOPOOLPERM))
                return 0;

        spin_lock(&ci->i_ceph_lock);
        flags = ci->i_ceph_flags;
        pool = ci->i_layout.pool_id;
        spin_unlock(&ci->i_ceph_lock);
check:
        if (flags & CEPH_I_POOL_PERM) {
                if ((need & CEPH_CAP_FILE_RD) && !(flags & CEPH_I_POOL_RD)) {
                        dout("ceph_pool_perm_check pool %lld no read perm\n",
                             pool);
                        return -EPERM;
                }
                if ((need & CEPH_CAP_FILE_WR) && !(flags & CEPH_I_POOL_WR)) {
                        dout("ceph_pool_perm_check pool %lld no write perm\n",
                             pool);
                        return -EPERM;
                }
                return 0;
        }

        pool_ns = ceph_try_get_string(ci->i_layout.pool_ns);
        ret = __ceph_pool_perm_get(ci, pool, pool_ns);
        ceph_put_string(pool_ns);
        if (ret < 0)
                return ret;

        flags = CEPH_I_POOL_PERM;
        if (ret & POOL_READ)
                flags |= CEPH_I_POOL_RD;
        if (ret & POOL_WRITE)
                flags |= CEPH_I_POOL_WR;

        spin_lock(&ci->i_ceph_lock);
        if (pool == ci->i_layout.pool_id &&
            pool_ns == rcu_dereference_raw(ci->i_layout.pool_ns)) {
                ci->i_ceph_flags |= flags;
        } else {
                pool = ci->i_layout.pool_id;
                flags = ci->i_ceph_flags;
        }
        spin_unlock(&ci->i_ceph_lock);
        goto check;
}

void ceph_pool_perm_destroy(struct ceph_mds_client *mdsc)
{
        struct ceph_pool_perm *perm;
        struct rb_node *n;

        while (!RB_EMPTY_ROOT(&mdsc->pool_perm_tree)) {
                n = rb_first(&mdsc->pool_perm_tree);
                perm = rb_entry(n, struct ceph_pool_perm, node);
                rb_erase(n, &mdsc->pool_perm_tree);
                kfree(perm);
        }
}