// SPDX-License-Identifier: GPL-2.0
/*
 * linux/fs/ext4/page-io.c
 *
 * This contains the new page_io functions for ext4
 *
 * Written by Theodore Ts'o, 2010.
 */

#include <linux/fs.h>
#include <linux/time.h>
#include <linux/highuid.h>
#include <linux/pagemap.h>
#include <linux/quotaops.h>
#include <linux/string.h>
#include <linux/buffer_head.h>
#include <linux/writeback.h>
#include <linux/pagevec.h>
#include <linux/mpage.h>
#include <linux/namei.h>
#include <linux/uio.h>
#include <linux/bio.h>
#include <linux/workqueue.h>
#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/mm.h>
#include <linux/backing-dev.h>

#include "ext4_jbd2.h"
#include "xattr.h"
#include "acl.h"

static struct kmem_cache *io_end_cachep;
static struct kmem_cache *io_end_vec_cachep;

int __init ext4_init_pageio(void)
{
        io_end_cachep = KMEM_CACHE(ext4_io_end, SLAB_RECLAIM_ACCOUNT);
        if (io_end_cachep == NULL)
                return -ENOMEM;

        io_end_vec_cachep = KMEM_CACHE(ext4_io_end_vec, 0);
        if (io_end_vec_cachep == NULL) {
                kmem_cache_destroy(io_end_cachep);
                return -ENOMEM;
        }
        return 0;
}

void ext4_exit_pageio(void)
{
        kmem_cache_destroy(io_end_cachep);
        kmem_cache_destroy(io_end_vec_cachep);
}

struct ext4_io_end_vec *ext4_alloc_io_end_vec(ext4_io_end_t *io_end)
{
        struct ext4_io_end_vec *io_end_vec;

        io_end_vec = kmem_cache_zalloc(io_end_vec_cachep, GFP_NOFS);
        if (!io_end_vec)
                return ERR_PTR(-ENOMEM);
        INIT_LIST_HEAD(&io_end_vec->list);
        list_add_tail(&io_end_vec->list, &io_end->list_vec);
        return io_end_vec;
}

static void ext4_free_io_end_vec(ext4_io_end_t *io_end)
{
        struct ext4_io_end_vec *io_end_vec, *tmp;

        if (list_empty(&io_end->list_vec))
                return;
        list_for_each_entry_safe(io_end_vec, tmp, &io_end->list_vec, list) {
                list_del(&io_end_vec->list);
                kmem_cache_free(io_end_vec_cachep, io_end_vec);
        }
}

struct ext4_io_end_vec *ext4_last_io_end_vec(ext4_io_end_t *io_end)
{
        BUG_ON(list_empty(&io_end->list_vec));
        return list_last_entry(&io_end->list_vec, struct ext4_io_end_vec, list);
}

/*
 * Print an buffer I/O error compatible with the fs/buffer.c.  This
 * provides compatibility with dmesg scrapers that look for a specific
 * buffer I/O error message.  We really need a unified error reporting
 * structure to userspace ala Digital Unix's uerf system, but it's
 * probably not going to happen in my lifetime, due to LKML politics...
 */
static void buffer_io_error(struct buffer_head *bh)
{
        printk_ratelimited(KERN_ERR "Buffer I/O error on device %pg, logical block %llu\n",
                       bh->b_bdev,
                        (unsigned long long)bh->b_blocknr);
}

static void ext4_finish_bio(struct bio *bio)
{
        struct bio_vec *bvec;
        struct bvec_iter_all iter_all;

        bio_for_each_segment_all(bvec, bio, iter_all) {
                struct page *page = bvec->bv_page;
                struct page *bounce_page = NULL;
                struct buffer_head *bh, *head;
                unsigned bio_start = bvec->bv_offset;
                unsigned bio_end = bio_start + bvec->bv_len;
                unsigned under_io = 0;
                unsigned long flags;

                if (!page)
                        continue;

                if (fscrypt_is_bounce_page(page)) {
                        bounce_page = page;
                        page = fscrypt_pagecache_page(bounce_page);
                }

                if (bio->bi_status) {
                        SetPageError(page);
                        mapping_set_error(page->mapping, -EIO);
                }
                bh = head = page_buffers(page);
                /*
                 * We check all buffers in the page under b_uptodate_lock
                 * to avoid races with other end io clearing async_write flags
                 */
                spin_lock_irqsave(&head->b_uptodate_lock, flags);
                do {
                        if (bh_offset(bh) < bio_start ||
                            bh_offset(bh) + bh->b_size > bio_end) {
                                if (buffer_async_write(bh))
                                        under_io++;
                                continue;
                        }
                        clear_buffer_async_write(bh);
                        if (bio->bi_status)
                                buffer_io_error(bh);
                } while ((bh = bh->b_this_page) != head);
                spin_unlock_irqrestore(&head->b_uptodate_lock, flags);
                if (!under_io) {
                        fscrypt_free_bounce_page(bounce_page);
                        end_page_writeback(page);
                }
        }
}

static void ext4_release_io_end(ext4_io_end_t *io_end)
{
        struct bio *bio, *next_bio;

        BUG_ON(!list_empty(&io_end->list));
        BUG_ON(io_end->flag & EXT4_IO_END_UNWRITTEN);
        WARN_ON(io_end->handle);

        for (bio = io_end->bio; bio; bio = next_bio) {
                next_bio = bio->bi_private;
                ext4_finish_bio(bio);
                bio_put(bio);
        }
        ext4_free_io_end_vec(io_end);
        kmem_cache_free(io_end_cachep, io_end);
}

/*
 * Check a range of space and convert unwritten extents to written. Note that
 * we are protected from truncate touching same part of extent tree by the
 * fact that truncate code waits for all DIO to finish (thus exclusion from
 * direct IO is achieved) and also waits for PageWriteback bits. Thus we
 * cannot get to ext4_ext_truncate() before all IOs overlapping that range are
 * completed (happens from ext4_free_ioend()).
 */
static int ext4_end_io_end(ext4_io_end_t *io_end)
{
        struct inode *inode = io_end->inode;
        handle_t *handle = io_end->handle;
        int ret = 0;

        ext4_debug("ext4_end_io_nolock: io_end 0x%p from inode %lu,list->next 0x%p,"
                   "list->prev 0x%p\n",
                   io_end, inode->i_ino, io_end->list.next, io_end->list.prev);

        io_end->handle = NULL;  /* Following call will use up the handle */
        ret = ext4_convert_unwritten_io_end_vec(handle, io_end);
        if (ret < 0 && !ext4_forced_shutdown(EXT4_SB(inode->i_sb))) {
                ext4_msg(inode->i_sb, KERN_EMERG,
                         "failed to convert unwritten extents to written "
                         "extents -- potential data loss!  "
                         "(inode %lu, error %d)", inode->i_ino, ret);
        }
        ext4_clear_io_unwritten_flag(io_end);
        ext4_release_io_end(io_end);
        return ret;
}

static void dump_completed_IO(struct inode *inode, struct list_head *head)
{
#ifdef  EXT4FS_DEBUG
        struct list_head *cur, *before, *after;
        ext4_io_end_t *io_end, *io_end0, *io_end1;

        if (list_empty(head))
                return;

        ext4_debug("Dump inode %lu completed io list\n", inode->i_ino);
        list_for_each_entry(io_end, head, list) {
                cur = &io_end->list;
                before = cur->prev;
                io_end0 = container_of(before, ext4_io_end_t, list);
                after = cur->next;
                io_end1 = container_of(after, ext4_io_end_t, list);

                ext4_debug("io 0x%p from inode %lu,prev 0x%p,next 0x%p\n",
                            io_end, inode->i_ino, io_end0, io_end1);
        }
#endif
}

/* Add the io_end to per-inode completed end_io list. */
static void ext4_add_complete_io(ext4_io_end_t *io_end)
{
        struct ext4_inode_info *ei = EXT4_I(io_end->inode);
        struct ext4_sb_info *sbi = EXT4_SB(io_end->inode->i_sb);
        struct workqueue_struct *wq;
        unsigned long flags;

        /* Only reserved conversions from writeback should enter here */
        WARN_ON(!(io_end->flag & EXT4_IO_END_UNWRITTEN));
        WARN_ON(!io_end->handle && sbi->s_journal);
        spin_lock_irqsave(&ei->i_completed_io_lock, flags);
        wq = sbi->rsv_conversion_wq;
        if (list_empty(&ei->i_rsv_conversion_list))
                queue_work(wq, &ei->i_rsv_conversion_work);
        list_add_tail(&io_end->list, &ei->i_rsv_conversion_list);
        spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);
}

static int ext4_do_flush_completed_IO(struct inode *inode,
                                      struct list_head *head)
{
        ext4_io_end_t *io_end;
        struct list_head unwritten;
        unsigned long flags;
        struct ext4_inode_info *ei = EXT4_I(inode);
        int err, ret = 0;

        spin_lock_irqsave(&ei->i_completed_io_lock, flags);
        dump_completed_IO(inode, head);
        list_replace_init(head, &unwritten);
        spin_unlock_irqrestore(&ei->i_completed_io_lock, flags);

        while (!list_empty(&unwritten)) {
                io_end = list_entry(unwritten.next, ext4_io_end_t, list);
                BUG_ON(!(io_end->flag & EXT4_IO_END_UNWRITTEN));
                list_del_init(&io_end->list);

                err = ext4_end_io_end(io_end);
                if (unlikely(!ret && err))
                        ret = err;
        }
        return ret;
}

/*
 * work on completed IO, to convert unwritten extents to extents
 */
void ext4_end_io_rsv_work(struct work_struct *work)
{
        struct ext4_inode_info *ei = container_of(work, struct ext4_inode_info,
                                                  i_rsv_conversion_work);
        ext4_do_flush_completed_IO(&ei->vfs_inode, &ei->i_rsv_conversion_list);
}

ext4_io_end_t *ext4_init_io_end(struct inode *inode, gfp_t flags)
{
        ext4_io_end_t *io_end = kmem_cache_zalloc(io_end_cachep, flags);

        if (io_end) {
                io_end->inode = inode;
                INIT_LIST_HEAD(&io_end->list);
                INIT_LIST_HEAD(&io_end->list_vec);
                atomic_set(&io_end->count, 1);
        }
        return io_end;
}

void ext4_put_io_end_defer(ext4_io_end_t *io_end)
{
        if (atomic_dec_and_test(&io_end->count)) {
                if (!(io_end->flag & EXT4_IO_END_UNWRITTEN) ||
                                list_empty(&io_end->list_vec)) {
                        ext4_release_io_end(io_end);
                        return;
                }
                ext4_add_complete_io(io_end);
        }
}

int ext4_put_io_end(ext4_io_end_t *io_end)
{
        int err = 0;

        if (atomic_dec_and_test(&io_end->count)) {
                if (io_end->flag & EXT4_IO_END_UNWRITTEN) {
                        err = ext4_convert_unwritten_io_end_vec(io_end->handle,
                                                                io_end);
                        io_end->handle = NULL;
                        ext4_clear_io_unwritten_flag(io_end);
                }
                ext4_release_io_end(io_end);
        }
        return err;
}

ext4_io_end_t *ext4_get_io_end(ext4_io_end_t *io_end)
{
        atomic_inc(&io_end->count);
        return io_end;
}

/* BIO completion function for page writeback */
static void ext4_end_bio(struct bio *bio)
{
        ext4_io_end_t *io_end = bio->bi_private;
        sector_t bi_sector = bio->bi_iter.bi_sector;
        char b[BDEVNAME_SIZE];

        if (WARN_ONCE(!io_end, "io_end is NULL: %s: sector %Lu len %u err %d\n",
                      bio_devname(bio, b),
                      (long long) bio->bi_iter.bi_sector,
                      (unsigned) bio_sectors(bio),
                      bio->bi_status)) {
                ext4_finish_bio(bio);
                bio_put(bio);
                return;
        }
        bio->bi_end_io = NULL;

        if (bio->bi_status) {
                struct inode *inode = io_end->inode;

                ext4_warning(inode->i_sb, "I/O error %d writing to inode %lu "
                             "starting block %llu)",
                             bio->bi_status, inode->i_ino,
                             (unsigned long long)
                             bi_sector >> (inode->i_blkbits - 9));
                mapping_set_error(inode->i_mapping,
                                blk_status_to_errno(bio->bi_status));
        }

        if (io_end->flag & EXT4_IO_END_UNWRITTEN) {
                /*
                 * Link bio into list hanging from io_end. We have to do it
                 * atomically as bio completions can be racing against each
                 * other.
                 */
                bio->bi_private = xchg(&io_end->bio, bio);
                ext4_put_io_end_defer(io_end);
        } else {
                /*
                 * Drop io_end reference early. Inode can get freed once
                 * we finish the bio.
                 */
                ext4_put_io_end_defer(io_end);
                ext4_finish_bio(bio);
                bio_put(bio);
        }
}

void ext4_io_submit(struct ext4_io_submit *io)
{
        struct bio *bio = io->io_bio;

        if (bio) {
                int io_op_flags = io->io_wbc->sync_mode == WB_SYNC_ALL ?
                                  REQ_SYNC : 0;
                io->io_bio->bi_write_hint = io->io_end->inode->i_write_hint;
                bio_set_op_attrs(io->io_bio, REQ_OP_WRITE, io_op_flags);
                submit_bio(io->io_bio);
        }
        io->io_bio = NULL;
}

void ext4_io_submit_init(struct ext4_io_submit *io,
                         struct writeback_control *wbc)
{
        io->io_wbc = wbc;
        io->io_bio = NULL;
        io->io_end = NULL;
}

static void io_submit_init_bio(struct ext4_io_submit *io,
                               struct buffer_head *bh)
{
        struct bio *bio;

        /*
         * bio_alloc will _always_ be able to allocate a bio if
         * __GFP_DIRECT_RECLAIM is set, see comments for bio_alloc_bioset().
         */
        bio = bio_alloc(GFP_NOIO, BIO_MAX_PAGES);
        fscrypt_set_bio_crypt_ctx_bh(bio, bh, GFP_NOIO);
        bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
        bio_set_dev(bio, bh->b_bdev);
        bio->bi_end_io = ext4_end_bio;
        bio->bi_private = ext4_get_io_end(io->io_end);
        io->io_bio = bio;
        io->io_next_block = bh->b_blocknr;
        wbc_init_bio(io->io_wbc, bio);
}

static void io_submit_add_bh(struct ext4_io_submit *io,
                             struct inode *inode,
                             struct page *page,
                             struct buffer_head *bh)
{
        int ret;

        if (io->io_bio && (bh->b_blocknr != io->io_next_block ||
                           !fscrypt_mergeable_bio_bh(io->io_bio, bh))) {
submit_and_retry:
                ext4_io_submit(io);
        }
        if (io->io_bio == NULL) {
                io_submit_init_bio(io, bh);
                io->io_bio->bi_write_hint = inode->i_write_hint;
        }
        ret = bio_add_page(io->io_bio, page, bh->b_size, bh_offset(bh));
        if (ret != bh->b_size)
                goto submit_and_retry;
        wbc_account_cgroup_owner(io->io_wbc, page, bh->b_size);
        io->io_next_block++;
}

int ext4_bio_write_page(struct ext4_io_submit *io,
                        struct page *page,
                        int len,
                        struct writeback_control *wbc,
                        bool keep_towrite)
{
        struct page *bounce_page = NULL;
        struct inode *inode = page->mapping->host;
        unsigned block_start;
        struct buffer_head *bh, *head;
        int ret = 0;
        int nr_submitted = 0;
        int nr_to_submit = 0;

        BUG_ON(!PageLocked(page));
        BUG_ON(PageWriteback(page));

        if (keep_towrite)
                set_page_writeback_keepwrite(page);
        else
                set_page_writeback(page);
        ClearPageError(page);

        /*
         * Comments copied from block_write_full_page:
         *
         * The page straddles i_size.  It must be zeroed out on each and every
         * writepage invocation because it may be mmapped.  "A file is mapped
         * in multiples of the page size.  For a file that is not a multiple of
         * the page size, the remaining memory is zeroed when mapped, and
         * writes to that region are not written out to the file."
         */
        if (len < PAGE_SIZE)
                zero_user_segment(page, len, PAGE_SIZE);
        /*
         * In the first loop we prepare and mark buffers to submit. We have to
         * mark all buffers in the page before submitting so that
         * end_page_writeback() cannot be called from ext4_bio_end_io() when IO
         * on the first buffer finishes and we are still working on submitting
         * the second buffer.
         */
        bh = head = page_buffers(page);
        do {
                block_start = bh_offset(bh);
                if (block_start >= len) {
                        clear_buffer_dirty(bh);
                        set_buffer_uptodate(bh);
                        continue;
                }
                if (!buffer_dirty(bh) || buffer_delay(bh) ||
                    !buffer_mapped(bh) || buffer_unwritten(bh)) {
                        /* A hole? We can safely clear the dirty bit */
                        if (!buffer_mapped(bh))
                                clear_buffer_dirty(bh);
                        if (io->io_bio)
                                ext4_io_submit(io);
                        continue;
                }
                if (buffer_new(bh))
                        clear_buffer_new(bh);
                set_buffer_async_write(bh);
                nr_to_submit++;
        } while ((bh = bh->b_this_page) != head);

        bh = head = page_buffers(page);

        /*
         * If any blocks are being written to an encrypted file, encrypt them
         * into a bounce page.  For simplicity, just encrypt until the last
         * block which might be needed.  This may cause some unneeded blocks
         * (e.g. holes) to be unnecessarily encrypted, but this is rare and
         * can't happen in the common case of blocksize == PAGE_SIZE.
         */
        if (fscrypt_inode_uses_fs_layer_crypto(inode) && nr_to_submit) {
                gfp_t gfp_flags = GFP_NOFS;
                unsigned int enc_bytes = round_up(len, i_blocksize(inode));

                /*
                 * Since bounce page allocation uses a mempool, we can only use
                 * a waiting mask (i.e. request guaranteed allocation) on the
                 * first page of the bio.  Otherwise it can deadlock.
                 */
                if (io->io_bio)
                        gfp_flags = GFP_NOWAIT | __GFP_NOWARN;
        retry_encrypt:
                bounce_page = fscrypt_encrypt_pagecache_blocks(page, enc_bytes,
                                                               0, gfp_flags);
                if (IS_ERR(bounce_page)) {
                        ret = PTR_ERR(bounce_page);
                        if (ret == -ENOMEM &&
                            (io->io_bio || wbc->sync_mode == WB_SYNC_ALL)) {
                                gfp_flags = GFP_NOFS;
                                if (io->io_bio)
                                        ext4_io_submit(io);
                                else
                                        gfp_flags |= __GFP_NOFAIL;
                                congestion_wait(BLK_RW_ASYNC, HZ/50);
                                goto retry_encrypt;
                        }

                        printk_ratelimited(KERN_ERR "%s: ret = %d\n", __func__, ret);
                        redirty_page_for_writepage(wbc, page);
                        do {
                                clear_buffer_async_write(bh);
                                bh = bh->b_this_page;
                        } while (bh != head);
                        goto unlock;
                }
        }

        /* Now submit buffers to write */
        do {
                if (!buffer_async_write(bh))
                        continue;
                io_submit_add_bh(io, inode,
                                 bounce_page ? bounce_page : page, bh);
                nr_submitted++;
                clear_buffer_dirty(bh);
        } while ((bh = bh->b_this_page) != head);

unlock:
        unlock_page(page);
        /* Nothing submitted - we have to end page writeback */
        if (!nr_submitted)
                end_page_writeback(page);
        return ret;
}