When fetching the ctime's nsec value for a stat-like operation, do a
simple fetch first and avoid the atomic_fetch_or if the flag is already
set.
Suggested-by: Mateusz Guzik <mjguzik@xxxxxxxxx>
Signed-off-by: Jeff Layton <jlayton@xxxxxxxxxx>
---
I'm running tests on this now, but I don't expect any problems.
This is based on top of Christian's vfs.mgtime branch. It may be best to
squash this into 6feb43ecdd8e ("fs: add infrastructure for multigrain
timestamps").
---
To: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
To: Christian Brauner <brauner@xxxxxxxxxx>
To: Jan Kara <jack@xxxxxxx>
Cc: linux-fsdevel@xxxxxxxxxxxxxxx
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
fs/stat.c | 9 ++++++---
1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/fs/stat.c b/fs/stat.c
index f2bf7cca64b2..9eb6d9b2d010 100644
--- a/fs/stat.c
+++ b/fs/stat.c
@@ -35,8 +35,8 @@
* @inode: inode from which to grab the c/mtime
*
* Given @inode, grab the ctime and mtime out if it and store the result
- * in @stat. When fetching the value, flag it as queried so the next write
- * will ensure a distinct timestamp.
+ * in @stat. When fetching the value, flag it as QUERIED (if not already)
+ * so the next write will record a distinct timestamp.
*/
void fill_mg_cmtime(struct kstat *stat, u32 request_mask, struct inode *inode)
{
@@ -50,7 +50,10 @@ void fill_mg_cmtime(struct kstat *stat, u32 request_mask, struct inode *inode)
stat->mtime = inode_get_mtime(inode);
stat->ctime.tv_sec = inode->i_ctime_sec;
- stat->ctime.tv_nsec = ((u32)atomic_fetch_or(I_CTIME_QUERIED, pcn)) & ~I_CTIME_QUERIED;
+ stat->ctime.tv_nsec = (u32)atomic_read(pcn);
+ if (!(stat->ctime.tv_nsec & I_CTIME_QUERIED))
+ stat->ctime.tv_nsec = ((u32)atomic_fetch_or(I_CTIME_QUERIED, pcn));
+ stat->ctime.tv_nsec &= ~I_CTIME_QUERIED;
trace_fill_mg_cmtime(inode, &stat->ctime, &stat->mtime);
}
EXPORT_SYMBOL(fill_mg_cmtime);
---
base-commit: 9000eec2bdc08a0b9027427f9d3d9a3545694258
change-id: 20240809-mgtime-cbc2aa6dc0fe
Best regards,
--
Jeff Layton <jlayton@xxxxxxxxxx>
