[PATCH v3 03/11] fs: only specify I_DIRTY_TIME when needed in generic_update_time()

Eric Biggers
2021-01-12T19:05:07Z

generic_update_time() always passes I_DIRTY_TIME to
__mark_inode_dirty(), which doesn't really make sense because (a)
generic_update_time() might be asked to do only an i_version update, not
also a timestamps update; and (b) I_DIRTY_TIME is only supposed to be
set in i_state if the filesystem has lazytime enabled, so using it
unconditionally in generic_update_time() is inconsistent.

As a result there is a weird edge case where if only an i_version update
was requested (not also a timestamps update) but it is no longer needed
(i.e. inode_maybe_inc_iversion() returns false), then I_DIRTY_TIME will
be set in i_state even if the filesystem isn't mounted with lazytime.

Fix this by only passing I_DIRTY_TIME to __mark_inode_dirty() if the
timestamps were updated and the filesystem has lazytime enabled.

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
fs/inode.c | 38 ++++++++++++++++++++------------------
1 file changed, 20 insertions(+), 18 deletions(-)

diff --git a/fs/inode.c b/fs/inode.c
index 6442d97d9a4ab..d0fa43d8e9d5c 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1743,24 +1743,26 @@ static int relatime_need_update(struct vfsmount *mnt, struct inode *inode,

int generic_update_time(struct inode *inode, struct timespec64 *time, int flags)
{
- int iflags = I_DIRTY_TIME;
- bool dirty = false;
-
- if (flags & S_ATIME)
- inode->i_atime = *time;
- if (flags & S_VERSION)
- dirty = inode_maybe_inc_iversion(inode, false);
- if (flags & S_CTIME)
- inode->i_ctime = *time;
- if (flags & S_MTIME)
- inode->i_mtime = *time;
- if ((flags & (S_ATIME | S_CTIME | S_MTIME)) &&
- !(inode->i_sb->s_flags & SB_LAZYTIME))
- dirty = true;
-
- if (dirty)
- iflags |= I_DIRTY_SYNC;
- __mark_inode_dirty(inode, iflags);
+ int dirty_flags = 0;
+
+ if (flags & (S_ATIME | S_CTIME | S_MTIME)) {
+ if (flags & S_ATIME)
+ inode->i_atime = *time;
+ if (flags & S_CTIME)
+ inode->i_ctime = *time;
+ if (flags & S_MTIME)
+ inode->i_mtime = *time;
+
+ if (inode->i_sb->s_flags & SB_LAZYTIME)
+ dirty_flags |= I_DIRTY_TIME;
+ else
+ dirty_flags |= I_DIRTY_SYNC;
+ }
+
+ if ((flags & S_VERSION) && inode_maybe_inc_iversion(inode, false))
+ dirty_flags |= I_DIRTY_SYNC;
+
+ __mark_inode_dirty(inode, dirty_flags);
return 0;
}
EXPORT_SYMBOL(generic_update_time);
--
2.30.0