On 08/14, Chao Yu wrote:
> SQLite App GC Thread Shrinker
> - f2fs_ioc_start_atomic_write
>
> - f2fs_ioc_commit_atomic_write
> - f2fs_commit_atomic_write
> - filemap_write_and_wait_range
> : write atomic_file's data to cow_inode
> echo 3 > drop_caches
> - f2fs_gc
> - gc_data_segment
> - move_data_page
> - set_page_dirty
> : it may load data of previous
> transaction into pagecache.
> - f2fs_down_write(&fi->i_gc_rwsem[WRITE])
> - __f2fs_commit_atomic_write
> - f2fs_up_write(&fi->i_gc_rwsem[WRITE])
>
> During committing atomic_file, GC may be triggered to migrate
> atomic_file's block, so it may contain data of previous transaction
> in page cache, we should drop atomic_file's cache once it was
> migrated by GC.
>
> And also, we should writeback atomic_file and cow_file's data
> w/ i_gc_rwsem lock held, in order to avoid block address change
> during __f2fs_commit_atomic_write().
>
> Meahwhile, this patch adds f2fs_wait_on_block_writeback_range()
> to wait completion of block migration.
>
> Fixes: 3db1de0e582c ("f2fs: change the current atomic write way")
> Signed-off-by: Chao Yu <c...@kernel.org>
> ---
> v2:
> - fix error path handling.
> fs/f2fs/segment.c | 27 +++++++++++++++++++++++----
> 1 file changed, 23 insertions(+), 4 deletions(-)
>
> diff --git a/fs/f2fs/segment.c b/fs/f2fs/segment.c
> index 3aee71c9f3c6..a43054ab0cf1 100644
> --- a/fs/f2fs/segment.c
> +++ b/fs/f2fs/segment.c
> @@ -236,6 +236,9 @@ static int __replace_atomic_write_block(struct inode
> *inode, pgoff_t index,
> return err;
> }
>
> + if (__is_valid_data_blkaddr(dn.data_blkaddr))
> + f2fs_wait_on_block_writeback_range(inode, dn.data_blkaddr, 1);
> +
> if (recover) {
> /* dn.data_blkaddr is always valid */
> if (!__is_valid_data_blkaddr(new_addr)) {
> @@ -339,6 +342,9 @@ static int __f2fs_commit_atomic_write(struct inode *inode)
> goto out;
> }
>
> + f2fs_wait_on_block_writeback_range(cow_inode,
> + blkaddr, 1);
> +
> new = f2fs_kmem_cache_alloc(revoke_entry_slab, GFP_NOFS,
> true, NULL);
>
> @@ -379,16 +385,29 @@ int f2fs_commit_atomic_write(struct inode *inode)
> struct f2fs_inode_info *fi = F2FS_I(inode);
> int err;
>
> + f2fs_down_write(&fi->i_gc_rwsem[WRITE]);
> +
> err = filemap_write_and_wait_range(inode->i_mapping, 0, LLONG_MAX);
> if (err)
> - return err;
> + goto out;
>
> - f2fs_down_write(&fi->i_gc_rwsem[WRITE]);
> - f2fs_lock_op(sbi);
> + /* writeback GCing page of cow_inode */
> + err = filemap_write_and_wait_range(fi->cow_inode->i_mapping,
> + 0, LLONG_MAX);
> + if (err)
> + goto out;
>
> - err = __f2fs_commit_atomic_write(inode);
> + filemap_invalidate_lock(inode->i_mapping);
> +
> + /* don't allow clean page loaded by GC to pollute atomic_file */
> + truncate_pagecache(inode, 0);
Performance impact?
>
> + f2fs_lock_op(sbi);
> + err = __f2fs_commit_atomic_write(inode);
> f2fs_unlock_op(sbi);
> +
> + filemap_invalidate_unlock(inode->i_mapping);
> +out:
> f2fs_up_write(&fi->i_gc_rwsem[WRITE]);
>
> return err;
> --
> 2.40.1
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