// SPDX-License-Identifier: GPL-2.0-or-later
/* AFS filesystem file handling
 *
 * Copyright (C) 2002, 2007 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells (dhowells@redhat.com)
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/init.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/writeback.h>
#include <linux/gfp.h>
#include <linux/task_io_accounting_ops.h>
#include <linux/mm.h>
#include <linux/netfs.h>
#include "internal.h"

static int afs_file_mmap(struct file *file, struct vm_area_struct *vma);
static int afs_readpage(struct file *file, struct page *page);
static void afs_invalidatepage(struct page *page, unsigned int offset,
                               unsigned int length);
static int afs_releasepage(struct page *page, gfp_t gfp_flags);

static void afs_readahead(struct readahead_control *ractl);
static ssize_t afs_file_read_iter(struct kiocb *iocb, struct iov_iter *iter);
static void afs_vm_open(struct vm_area_struct *area);
static void afs_vm_close(struct vm_area_struct *area);
static vm_fault_t afs_vm_map_pages(struct vm_fault *vmf, pgoff_t start_pgoff, pgoff_t end_pgoff);

const struct file_operations afs_file_operations = {
        .open           = afs_open,
        .release        = afs_release,
        .llseek         = generic_file_llseek,
        .read_iter      = afs_file_read_iter,
        .write_iter     = afs_file_write,
        .mmap           = afs_file_mmap,
        .splice_read    = generic_file_splice_read,
        .splice_write   = iter_file_splice_write,
        .fsync          = afs_fsync,
        .lock           = afs_lock,
        .flock          = afs_flock,
};

const struct inode_operations afs_file_inode_operations = {
        .getattr        = afs_getattr,
        .setattr        = afs_setattr,
        .permission     = afs_permission,
};

const struct address_space_operations afs_fs_aops = {
        .readpage       = afs_readpage,
        .readahead      = afs_readahead,
        .set_page_dirty = afs_set_page_dirty,
        .launder_page   = afs_launder_page,
        .releasepage    = afs_releasepage,
        .invalidatepage = afs_invalidatepage,
        .write_begin    = afs_write_begin,
        .write_end      = afs_write_end,
        .writepage      = afs_writepage,
        .writepages     = afs_writepages,
};

static const struct vm_operations_struct afs_vm_ops = {
        .open           = afs_vm_open,
        .close          = afs_vm_close,
        .fault          = filemap_fault,
        .map_pages      = afs_vm_map_pages,
        .page_mkwrite   = afs_page_mkwrite,
};

/*
 * Discard a pin on a writeback key.
 */
void afs_put_wb_key(struct afs_wb_key *wbk)
{
        if (wbk && refcount_dec_and_test(&wbk->usage)) {
                key_put(wbk->key);
                kfree(wbk);
        }
}

/*
 * Cache key for writeback.
 */
int afs_cache_wb_key(struct afs_vnode *vnode, struct afs_file *af)
{
        struct afs_wb_key *wbk, *p;

        wbk = kzalloc(sizeof(struct afs_wb_key), GFP_KERNEL);
        if (!wbk)
                return -ENOMEM;
        refcount_set(&wbk->usage, 2);
        wbk->key = af->key;

        spin_lock(&vnode->wb_lock);
        list_for_each_entry(p, &vnode->wb_keys, vnode_link) {
                if (p->key == wbk->key)
                        goto found;
        }

        key_get(wbk->key);
        list_add_tail(&wbk->vnode_link, &vnode->wb_keys);
        spin_unlock(&vnode->wb_lock);
        af->wb = wbk;
        return 0;

found:
        refcount_inc(&p->usage);
        spin_unlock(&vnode->wb_lock);
        af->wb = p;
        kfree(wbk);
        return 0;
}

/*
 * open an AFS file or directory and attach a key to it
 */
int afs_open(struct inode *inode, struct file *file)
{
        struct afs_vnode *vnode = AFS_FS_I(inode);
        struct afs_file *af;
        struct key *key;
        int ret;

        _enter("{%llx:%llu},", vnode->fid.vid, vnode->fid.vnode);

        key = afs_request_key(vnode->volume->cell);
        if (IS_ERR(key)) {
                ret = PTR_ERR(key);
                goto error;
        }

        af = kzalloc(sizeof(*af), GFP_KERNEL);
        if (!af) {
                ret = -ENOMEM;
                goto error_key;
        }
        af->key = key;

        ret = afs_validate(vnode, key);
        if (ret < 0)
                goto error_af;

        if (file->f_mode & FMODE_WRITE) {
                ret = afs_cache_wb_key(vnode, af);
                if (ret < 0)
                        goto error_af;
        }

        if (file->f_flags & O_TRUNC)
                set_bit(AFS_VNODE_NEW_CONTENT, &vnode->flags);
        
        file->private_data = af;
        _leave(" = 0");
        return 0;

error_af:
        kfree(af);
error_key:
        key_put(key);
error:
        _leave(" = %d", ret);
        return ret;
}

/*
 * release an AFS file or directory and discard its key
 */
int afs_release(struct inode *inode, struct file *file)
{
        struct afs_vnode *vnode = AFS_FS_I(inode);
        struct afs_file *af = file->private_data;
        int ret = 0;

        _enter("{%llx:%llu},", vnode->fid.vid, vnode->fid.vnode);

        if ((file->f_mode & FMODE_WRITE))
                ret = vfs_fsync(file, 0);

        file->private_data = NULL;
        if (af->wb)
                afs_put_wb_key(af->wb);
        key_put(af->key);
        kfree(af);
        afs_prune_wb_keys(vnode);
        _leave(" = %d", ret);
        return ret;
}

/*
 * Allocate a new read record.
 */
struct afs_read *afs_alloc_read(gfp_t gfp)
{
        struct afs_read *req;

        req = kzalloc(sizeof(struct afs_read), gfp);
        if (req)
                refcount_set(&req->usage, 1);

        return req;
}

/*
 * Dispose of a ref to a read record.
 */
void afs_put_read(struct afs_read *req)
{
        if (refcount_dec_and_test(&req->usage)) {
                if (req->cleanup)
                        req->cleanup(req);
                key_put(req->key);
                kfree(req);
        }
}

static void afs_fetch_data_notify(struct afs_operation *op)
{
        struct afs_read *req = op->fetch.req;
        struct netfs_read_subrequest *subreq = req->subreq;
        int error = op->error;

        if (error == -ECONNABORTED)
                error = afs_abort_to_error(op->ac.abort_code);
        req->error = error;

        if (subreq) {
                __set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
                netfs_subreq_terminated(subreq, error ?: req->actual_len, false);
                req->subreq = NULL;
        } else if (req->done) {
                req->done(req);
        }
}

static void afs_fetch_data_success(struct afs_operation *op)
{
        struct afs_vnode *vnode = op->file[0].vnode;

        _enter("op=%08x", op->debug_id);
        afs_vnode_commit_status(op, &op->file[0]);
        afs_stat_v(vnode, n_fetches);
        atomic_long_add(op->fetch.req->actual_len, &op->net->n_fetch_bytes);
        afs_fetch_data_notify(op);
}

static void afs_fetch_data_put(struct afs_operation *op)
{
        op->fetch.req->error = op->error;
        afs_put_read(op->fetch.req);
}

static const struct afs_operation_ops afs_fetch_data_operation = {
        .issue_afs_rpc  = afs_fs_fetch_data,
        .issue_yfs_rpc  = yfs_fs_fetch_data,
        .success        = afs_fetch_data_success,
        .aborted        = afs_check_for_remote_deletion,
        .failed         = afs_fetch_data_notify,
        .put            = afs_fetch_data_put,
};

/*
 * Fetch file data from the volume.
 */
int afs_fetch_data(struct afs_vnode *vnode, struct afs_read *req)
{
        struct afs_operation *op;

        _enter("%s{%llx:%llu.%u},%x,,,",
               vnode->volume->name,
               vnode->fid.vid,
               vnode->fid.vnode,
               vnode->fid.unique,
               key_serial(req->key));

        op = afs_alloc_operation(req->key, vnode->volume);
        if (IS_ERR(op)) {
                if (req->subreq)
                        netfs_subreq_terminated(req->subreq, PTR_ERR(op), false);
                return PTR_ERR(op);
        }

        afs_op_set_vnode(op, 0, vnode);

        op->fetch.req   = afs_get_read(req);
        op->ops         = &afs_fetch_data_operation;
        return afs_do_sync_operation(op);
}

static void afs_req_issue_op(struct netfs_read_subrequest *subreq)
{
        struct afs_vnode *vnode = AFS_FS_I(subreq->rreq->inode);
        struct afs_read *fsreq;

        fsreq = afs_alloc_read(GFP_NOFS);
        if (!fsreq)
                return netfs_subreq_terminated(subreq, -ENOMEM, false);

        fsreq->subreq   = subreq;
        fsreq->pos      = subreq->start + subreq->transferred;
        fsreq->len      = subreq->len   - subreq->transferred;
        fsreq->key      = key_get(subreq->rreq->netfs_priv);
        fsreq->vnode    = vnode;
        fsreq->iter     = &fsreq->def_iter;

        iov_iter_xarray(&fsreq->def_iter, READ,
                        &fsreq->vnode->vfs_inode.i_mapping->i_pages,
                        fsreq->pos, fsreq->len);

        afs_fetch_data(fsreq->vnode, fsreq);
        afs_put_read(fsreq);
}

static int afs_symlink_readpage(struct page *page)
{
        struct afs_vnode *vnode = AFS_FS_I(page->mapping->host);
        struct afs_read *fsreq;
        int ret;

        fsreq = afs_alloc_read(GFP_NOFS);
        if (!fsreq)
                return -ENOMEM;

        fsreq->pos      = page->index * PAGE_SIZE;
        fsreq->len      = PAGE_SIZE;
        fsreq->vnode    = vnode;
        fsreq->iter     = &fsreq->def_iter;
        iov_iter_xarray(&fsreq->def_iter, READ, &page->mapping->i_pages,
                        fsreq->pos, fsreq->len);

        ret = afs_fetch_data(fsreq->vnode, fsreq);
        page_endio(page, false, ret);
        return ret;
}

static void afs_init_rreq(struct netfs_read_request *rreq, struct file *file)
{
        rreq->netfs_priv = key_get(afs_file_key(file));
}

static bool afs_is_cache_enabled(struct inode *inode)
{
        struct fscache_cookie *cookie = afs_vnode_cache(AFS_FS_I(inode));

        return fscache_cookie_enabled(cookie) && !hlist_empty(&cookie->backing_objects);
}

static int afs_begin_cache_operation(struct netfs_read_request *rreq)
{
        struct afs_vnode *vnode = AFS_FS_I(rreq->inode);

        return fscache_begin_read_operation(rreq, afs_vnode_cache(vnode));
}

static int afs_check_write_begin(struct file *file, loff_t pos, unsigned len,
                                 struct page *page, void **_fsdata)
{
        struct afs_vnode *vnode = AFS_FS_I(file_inode(file));

        return test_bit(AFS_VNODE_DELETED, &vnode->flags) ? -ESTALE : 0;
}

static void afs_priv_cleanup(struct address_space *mapping, void *netfs_priv)
{
        key_put(netfs_priv);
}

const struct netfs_read_request_ops afs_req_ops = {
        .init_rreq              = afs_init_rreq,
        .is_cache_enabled       = afs_is_cache_enabled,
        .begin_cache_operation  = afs_begin_cache_operation,
        .check_write_begin      = afs_check_write_begin,
        .issue_op               = afs_req_issue_op,
        .cleanup                = afs_priv_cleanup,
};

static int afs_readpage(struct file *file, struct page *page)
{
        if (!file)
                return afs_symlink_readpage(page);

        return netfs_readpage(file, page, &afs_req_ops, NULL);
}

static void afs_readahead(struct readahead_control *ractl)
{
        netfs_readahead(ractl, &afs_req_ops, NULL);
}

/*
 * Adjust the dirty region of the page on truncation or full invalidation,
 * getting rid of the markers altogether if the region is entirely invalidated.
 */
static void afs_invalidate_dirty(struct page *page, unsigned int offset,
                                 unsigned int length)
{
        struct afs_vnode *vnode = AFS_FS_I(page->mapping->host);
        unsigned long priv;
        unsigned int f, t, end = offset + length;

        priv = page_private(page);

        /* we clean up only if the entire page is being invalidated */
        if (offset == 0 && length == thp_size(page))
                goto full_invalidate;

         /* If the page was dirtied by page_mkwrite(), the PTE stays writable
          * and we don't get another notification to tell us to expand it
          * again.
          */
        if (afs_is_page_dirty_mmapped(priv))
                return;

        /* We may need to shorten the dirty region */
        f = afs_page_dirty_from(page, priv);
        t = afs_page_dirty_to(page, priv);

        if (t <= offset || f >= end)
                return; /* Doesn't overlap */

        if (f < offset && t > end)
                return; /* Splits the dirty region - just absorb it */

        if (f >= offset && t <= end)
                goto undirty;

        if (f < offset)
                t = offset;
        else
                f = end;
        if (f == t)
                goto undirty;

        priv = afs_page_dirty(page, f, t);
        set_page_private(page, priv);
        trace_afs_page_dirty(vnode, tracepoint_string("trunc"), page);
        return;

undirty:
        trace_afs_page_dirty(vnode, tracepoint_string("undirty"), page);
        clear_page_dirty_for_io(page);
full_invalidate:
        trace_afs_page_dirty(vnode, tracepoint_string("inval"), page);
        detach_page_private(page);
}

/*
 * invalidate part or all of a page
 * - release a page and clean up its private data if offset is 0 (indicating
 *   the entire page)
 */
static void afs_invalidatepage(struct page *page, unsigned int offset,
                               unsigned int length)
{
        _enter("{%lu},%u,%u", page->index, offset, length);

        BUG_ON(!PageLocked(page));

        if (PagePrivate(page))
                afs_invalidate_dirty(page, offset, length);

        wait_on_page_fscache(page);
        _leave("");
}

/*
 * release a page and clean up its private state if it's not busy
 * - return true if the page can now be released, false if not
 */
static int afs_releasepage(struct page *page, gfp_t gfp_flags)
{
        struct afs_vnode *vnode = AFS_FS_I(page->mapping->host);

        _enter("{{%llx:%llu}[%lu],%lx},%x",
               vnode->fid.vid, vnode->fid.vnode, page->index, page->flags,
               gfp_flags);

        /* deny if page is being written to the cache and the caller hasn't
         * elected to wait */
#ifdef CONFIG_AFS_FSCACHE
        if (PageFsCache(page)) {
                if (!(gfp_flags & __GFP_DIRECT_RECLAIM) || !(gfp_flags & __GFP_FS))
                        return false;
                wait_on_page_fscache(page);
        }
#endif

        if (PagePrivate(page)) {
                trace_afs_page_dirty(vnode, tracepoint_string("rel"), page);
                detach_page_private(page);
        }

        /* indicate that the page can be released */
        _leave(" = T");
        return 1;
}

static void afs_add_open_mmap(struct afs_vnode *vnode)
{
        if (atomic_inc_return(&vnode->cb_nr_mmap) == 1) {
                down_write(&vnode->volume->cell->fs_open_mmaps_lock);

                list_add_tail(&vnode->cb_mmap_link,
                              &vnode->volume->cell->fs_open_mmaps);

                up_write(&vnode->volume->cell->fs_open_mmaps_lock);
        }
}

static void afs_drop_open_mmap(struct afs_vnode *vnode)
{
        if (!atomic_dec_and_test(&vnode->cb_nr_mmap))
                return;

        down_write(&vnode->volume->cell->fs_open_mmaps_lock);

        if (atomic_read(&vnode->cb_nr_mmap) == 0)
                list_del_init(&vnode->cb_mmap_link);

        up_write(&vnode->volume->cell->fs_open_mmaps_lock);
        flush_work(&vnode->cb_work);
}

/*
 * Handle setting up a memory mapping on an AFS file.
 */
static int afs_file_mmap(struct file *file, struct vm_area_struct *vma)
{
        struct afs_vnode *vnode = AFS_FS_I(file_inode(file));
        int ret;

        afs_add_open_mmap(vnode);

        ret = generic_file_mmap(file, vma);
        if (ret == 0)
                vma->vm_ops = &afs_vm_ops;
        else
                afs_drop_open_mmap(vnode);
        return ret;
}

static void afs_vm_open(struct vm_area_struct *vma)
{
        afs_add_open_mmap(AFS_FS_I(file_inode(vma->vm_file)));
}

static void afs_vm_close(struct vm_area_struct *vma)
{
        afs_drop_open_mmap(AFS_FS_I(file_inode(vma->vm_file)));
}

static vm_fault_t afs_vm_map_pages(struct vm_fault *vmf, pgoff_t start_pgoff, pgoff_t end_pgoff)
{
        struct afs_vnode *vnode = AFS_FS_I(file_inode(vmf->vma->vm_file));
        struct afs_file *af = vmf->vma->vm_file->private_data;

        switch (afs_validate(vnode, af->key)) {
        case 0:
                return filemap_map_pages(vmf, start_pgoff, end_pgoff);
        case -ENOMEM:
                return VM_FAULT_OOM;
        case -EINTR:
        case -ERESTARTSYS:
                return VM_FAULT_RETRY;
        case -ESTALE:
        default:
                return VM_FAULT_SIGBUS;
        }
}

static ssize_t afs_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
{
        struct afs_vnode *vnode = AFS_FS_I(file_inode(iocb->ki_filp));
        struct afs_file *af = iocb->ki_filp->private_data;
        int ret;

        ret = afs_validate(vnode, af->key);
        if (ret < 0)
                return ret;

        return generic_file_read_iter(iocb, iter);
}