From: Chao Yu <yuch...@huawei.com>

Thread A                        Thread B
- f2fs_release_file
 - clear_inode_flag(FI_VOLATILE_FILE)
                                - wb_writeback
                                 - writeback_sb_inodes
                                  - __writeback_single_inode
                                   - do_writepages
                                    - f2fs_write_data_pages
                                     - __write_data_page
                                     all volatile file's pages
                                     are writebacked to storage
 - set_inode_flag(FI_DROP_CACHE)
 - filemap_fdatawrite

There is a hole that mm can flush all dirty pages of volatile file as
inode is not tagged with both FI_VOLATILE_FILE and FI_DROP_CACHE flags,
we should never writeback the page #0 and also it's unneeded to writeback
other pages.

This patch adjusts to relocate clear_inode_flag(FI_VOLATILE_FILE), so that
FI_VOLATILE_FILE flag can be remained before all dirty pages were dropped
to avoid issue.

Signed-off-by: Chao Yu <yuch...@huawei.com>
---
 fs/f2fs/file.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c
index 16fd50abbf40..13f2f6845e87 100644
--- a/fs/f2fs/file.c
+++ b/fs/f2fs/file.c
@@ -1564,11 +1564,11 @@ static int f2fs_release_file(struct inode *inode, 
struct file *filp)
        if (f2fs_is_atomic_file(inode))
                f2fs_drop_inmem_pages(inode);
        if (f2fs_is_volatile_file(inode)) {
-               clear_inode_flag(inode, FI_VOLATILE_FILE);
-               stat_dec_volatile_write(inode);
                set_inode_flag(inode, FI_DROP_CACHE);
                filemap_fdatawrite(inode->i_mapping);
                clear_inode_flag(inode, FI_DROP_CACHE);
+               clear_inode_flag(inode, FI_VOLATILE_FILE);
+               stat_dec_volatile_write(inode);
        }
        return 0;
 }
-- 
2.16.2.17.g38e79b1fd


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