[PATCH 12/14] fs: add support for non-blocking timestamp updates

Christoph Hellwig
2025-11-14T06:28:18Z

Currently file_update_time_flags unconditionally returns -EAGAIN if any
timestamp needs to be updated and IOCB_NOWAIT is passed. This makes
non-blocking direct writes impossible on file systems with granular
enough timestamps.

Add a S_NOWAIT to ask for timestamps to not block, and return -EAGAIN in
all methods for now.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
fs/btrfs/inode.c | 3 +++
fs/fat/misc.c | 3 +++
fs/gfs2/inode.c | 3 +++
fs/inode.c | 5 ++++-
fs/orangefs/inode.c | 3 +++
fs/overlayfs/inode.c | 3 +++
fs/ubifs/file.c | 3 +++
fs/xfs/xfs_iops.c | 3 +++
include/linux/fs.h | 10 ++++++----
9 files changed, 31 insertions(+), 5 deletions(-)

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 6282911e536f..dea798d325d1 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -6302,6 +6302,9 @@ static int btrfs_update_time(struct inode *inode, int flags)
if (btrfs_root_readonly(root))
return -EROFS;

+ if (flags & S_NOWAIT)
+ return -EAGAIN;
+
dirty = inode_update_timestamps(inode, flags);
return dirty ? btrfs_dirty_inode(BTRFS_I(inode)) : 0;
}
diff --git a/fs/fat/misc.c b/fs/fat/misc.c
index 950da09f0961..5df3193c35f9 100644
--- a/fs/fat/misc.c
+++ b/fs/fat/misc.c
@@ -346,6 +346,9 @@ int fat_update_time(struct inode *inode, int flags)
if (inode->i_ino == MSDOS_ROOT_INO)
return 0;

+ if (flags & S_NOWAIT)
+ return -EAGAIN;
+
if (flags & (S_ATIME | S_CTIME | S_MTIME)) {
fat_truncate_time(inode, NULL, flags);
if (inode->i_sb->s_flags & SB_LAZYTIME)
diff --git a/fs/gfs2/inode.c b/fs/gfs2/inode.c
index 601c14a3ac77..0184cb64fe9f 100644
--- a/fs/gfs2/inode.c
+++ b/fs/gfs2/inode.c
@@ -2234,6 +2234,9 @@ static int gfs2_update_time(struct inode *inode, int flags)
struct gfs2_holder *gh;
int error;

+ if (flags & S_NOWAIT)
+ return -EAGAIN;
+
gh = gfs2_glock_is_locked_by_me(gl);
if (gh && gl->gl_state != LM_ST_EXCLUSIVE) {
gfs2_glock_dq(gh);
diff --git a/fs/inode.c b/fs/inode.c
index 34d572c99313..dc6bb6236361 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -2092,6 +2092,9 @@ EXPORT_SYMBOL(inode_update_timestamps);
*/
int generic_update_time(struct inode *inode, int flags)
{
+ if (flags & S_NOWAIT)
+ return -EAGAIN;
+
flags = inode_update_timestamps(inode, flags);
if (flags)
mark_inode_dirty_time(inode, flags);
@@ -2320,7 +2323,7 @@ static int file_update_time_flags(struct file *file, unsigned int flags)
return 0;

if (flags & IOCB_NOWAIT)
- return -EAGAIN;
+ sync_mode |= S_NOWAIT;

if (mnt_get_write_access_file(file))
return 0;
diff --git a/fs/orangefs/inode.c b/fs/orangefs/inode.c
index 55f6c8026812..9abd4153c85d 100644
--- a/fs/orangefs/inode.c
+++ b/fs/orangefs/inode.c
@@ -879,6 +879,9 @@ int orangefs_update_time(struct inode *inode, int flags)
gossip_debug(GOSSIP_INODE_DEBUG, "orangefs_update_time: %pU\n",
get_khandle_from_ino(inode));

+ if (flags & S_NOWAIT)
+ return -EAGAIN;
+
flags = inode_update_timestamps(inode, flags);

memset(&iattr, 0, sizeof iattr);
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index e11f310ce092..c132d1f5502b 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -576,6 +576,9 @@ int ovl_update_time(struct inode *inode, int flags)
.dentry = ovl_upperdentry_dereference(OVL_I(inode)),
};

+ if (flags & S_NOWAIT)
+ return -EAGAIN;
+
if (upperpath.dentry) {
touch_atime(&upperpath);
inode_set_atime_to_ts(inode,
diff --git a/fs/ubifs/file.c b/fs/ubifs/file.c
index 3e119cb93ea9..1caa2a93eaf5 100644
--- a/fs/ubifs/file.c
+++ b/fs/ubifs/file.c
@@ -1382,6 +1382,9 @@ int ubifs_update_time(struct inode *inode, int flags)
if (!IS_ENABLED(CONFIG_UBIFS_ATIME_SUPPORT))
return generic_update_time(inode, flags);

+ if (flags & S_NOWAIT)
+ return -EAGAIN;
+
err = ubifs_budget_space(c, &req);
if (err)
return err;
diff --git a/fs/xfs/xfs_iops.c b/fs/xfs/xfs_iops.c
index 0ace5f790006..da055dade25f 100644
--- a/fs/xfs/xfs_iops.c
+++ b/fs/xfs/xfs_iops.c
@@ -1195,6 +1195,9 @@ xfs_vn_update_time(

trace_xfs_update_time(ip);

+ if (flags & S_NOWAIT)
+ return -EAGAIN;
+
if (inode->i_sb->s_flags & SB_LAZYTIME) {
if (!((flags & S_VERSION) &&
inode_maybe_inc_iversion(inode, false)))
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 61051c86dbd2..36592fac1887 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2659,10 +2659,12 @@ static inline void inode_dec_link_count(struct inode *inode)
}

enum file_time_flags {
- S_ATIME = 1,
- S_MTIME = 2,
- S_CTIME = 4,
- S_VERSION = 8,
+ S_ATIME = 1U << 0,
+ S_MTIME = 1U << 1,
+ S_CTIME = 1U << 2,
+ S_VERSION = 1U << 4,
+
+ S_NOWAIT = 1U << 15,
};

extern bool atime_needs_update(const struct path *, struct inode *);
--
2.47.3