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Subject[PATCH] f2fs: fix to update time in lazytime mode
Date
generic/018 reports an inconsistent status of atime, the
testcase is as below:
- open file with O_SYNC
- write file to construct fraged space
- calc md5 of file
- record {a,c,m}time
- defrag file --- do nothing
- umount & mount
- check {a,c,m}time

The root cause is, as f2fs enables lazytime by default, atime
update will dirty vfs inode, rather than dirtying f2fs inode (by set
with FI_DIRTY_INODE), so later f2fs_write_inode() called from VFS will
fail to update inode page due to our skip:

f2fs_write_inode()
if (is_inode_flag_set(inode, FI_DIRTY_INODE))
return 0;

So eventually, after evict(), we lose last atime for ever.

To fix this issue, we need to check whether {a,c,m,cr}time is
consistent in between inode cache and inode page, and only skip
f2fs_update_inode() if f2fs inode is not dirty and time is
consistent as well.

Signed-off-by: Chao Yu <yuchao0@huawei.com>
---
fs/f2fs/f2fs.h | 23 +++++++++++++++--------
fs/f2fs/inode.c | 6 +++++-
2 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h
index bc7d7ab70dea..a2f6403bdcb0 100644
--- a/fs/f2fs/f2fs.h
+++ b/fs/f2fs/f2fs.h
@@ -2709,6 +2709,20 @@ static inline void clear_file(struct inode *inode, int type)
f2fs_mark_inode_dirty_sync(inode, true);
}

+static inline bool f2fs_is_time_consistent(struct inode *inode)
+{
+ if (!timespec64_equal(F2FS_I(inode)->i_disk_time, &inode->i_atime))
+ return false;
+ if (!timespec64_equal(F2FS_I(inode)->i_disk_time + 1, &inode->i_ctime))
+ return false;
+ if (!timespec64_equal(F2FS_I(inode)->i_disk_time + 2, &inode->i_mtime))
+ return false;
+ if (!timespec64_equal(F2FS_I(inode)->i_disk_time + 3,
+ &F2FS_I(inode)->i_crtime))
+ return false;
+ return true;
+}
+
static inline bool f2fs_skip_inode_update(struct inode *inode, int dsync)
{
bool ret;
@@ -2726,14 +2740,7 @@ static inline bool f2fs_skip_inode_update(struct inode *inode, int dsync)
i_size_read(inode) & ~PAGE_MASK)
return false;

- if (!timespec64_equal(F2FS_I(inode)->i_disk_time, &inode->i_atime))
- return false;
- if (!timespec64_equal(F2FS_I(inode)->i_disk_time + 1, &inode->i_ctime))
- return false;
- if (!timespec64_equal(F2FS_I(inode)->i_disk_time + 2, &inode->i_mtime))
- return false;
- if (!timespec64_equal(F2FS_I(inode)->i_disk_time + 3,
- &F2FS_I(inode)->i_crtime))
+ if (!f2fs_is_time_consistent(inode))
return false;

down_read(&F2FS_I(inode)->i_sem);
diff --git a/fs/f2fs/inode.c b/fs/f2fs/inode.c
index 137ba1c6873d..540280cee614 100644
--- a/fs/f2fs/inode.c
+++ b/fs/f2fs/inode.c
@@ -615,7 +615,11 @@ int f2fs_write_inode(struct inode *inode, struct writeback_control *wbc)
inode->i_ino == F2FS_META_INO(sbi))
return 0;

- if (!is_inode_flag_set(inode, FI_DIRTY_INODE))
+ /*
+ * atime could be updated without dirtying f2fs inode in lazytime mode
+ */
+ if (f2fs_is_time_consistent(inode) &&
+ !is_inode_flag_set(inode, FI_DIRTY_INODE))
return 0;

if (!f2fs_is_checkpoint_ready(sbi))
--
2.18.0.rc1
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