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Message-ID: <20251120064859.2911749-15-hch@lst.de>
Date: Thu, 20 Nov 2025 07:47:35 +0100
From: Christoph Hellwig <hch@....de>
To: Christian Brauner <brauner@...nel.org>
Cc: Al Viro <viro@...iv.linux.org.uk>,
David Sterba <dsterba@...e.com>,
Jan Kara <jack@...e.cz>,
Mike Marshall <hubcap@...ibond.com>,
Martin Brandenburg <martin@...ibond.com>,
Carlos Maiolino <cem@...nel.org>,
Stefan Roesch <shr@...com>,
Jeff Layton <jlayton@...nel.org>,
linux-kernel@...r.kernel.org,
linux-btrfs@...r.kernel.org,
linux-fsdevel@...r.kernel.org,
gfs2@...ts.linux.dev,
io-uring@...r.kernel.org,
devel@...ts.orangefs.org,
linux-unionfs@...r.kernel.org,
linux-mtd@...ts.infradead.org,
linux-xfs@...r.kernel.org,
linux-nfs@...r.kernel.org
Subject: [PATCH 14/16] fs: add support for non-blocking timestamp updates
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@....de>
Reviewed-by: Jeff Layton <jlayton@...nel.org>
---
fs/btrfs/inode.c | 3 +++
fs/fat/misc.c | 3 +++
fs/gfs2/inode.c | 3 +++
fs/inode.c | 30 +++++++++++++++++++++++++-----
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, 52 insertions(+), 9 deletions(-)
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 668e4a1df7ae..ea7e87bce1cd 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;
+
error = inode_update_timestamps(inode, &flags);
if (error || !flags)
return error;
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 156a5fb50c7e..577eea4e9704 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -2072,12 +2072,26 @@ int inode_update_timestamps(struct inode *inode, int *flags)
now = inode_set_ctime_current(inode);
if (!timespec64_equal(&now, &ctime))
updated |= S_CTIME;
- if (!timespec64_equal(&now, &mtime)) {
- inode_set_mtime_to_ts(inode, now);
+ if (!timespec64_equal(&now, &mtime))
updated |= S_MTIME;
+
+ if (IS_I_VERSION(inode)) {
+ if (*flags & S_NOWAIT) {
+ /*
+ * Error out if we'd need timestamp updates, as
+ * the generally requires blocking to dirty the
+ * inode in one form or another.
+ */
+ if (updated && inode_iversion_need_inc(inode))
+ goto bail;
+ } else {
+ if (inode_maybe_inc_iversion(inode, updated))
+ updated |= S_VERSION;
+ }
}
- if (IS_I_VERSION(inode) && inode_maybe_inc_iversion(inode, updated))
- updated |= S_VERSION;
+
+ if (updated & S_MTIME)
+ inode_set_mtime_to_ts(inode, now);
} else {
now = current_time(inode);
}
@@ -2093,6 +2107,9 @@ int inode_update_timestamps(struct inode *inode, int *flags)
*flags = updated;
return 0;
+bail:
+ *flags = 0;
+ return -EAGAIN;
}
EXPORT_SYMBOL(inode_update_timestamps);
@@ -2112,6 +2129,9 @@ int generic_update_time(struct inode *inode, int flags)
{
int error;
+ if (flags & S_NOWAIT)
+ return -EAGAIN;
+
error = inode_update_timestamps(inode, &flags);
if (!error && flags)
mark_inode_dirty_time(inode, flags);
@@ -2340,7 +2360,7 @@ 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 ec56a777053d..569280935179 100644
--- a/fs/orangefs/inode.c
+++ b/fs/orangefs/inode.c
@@ -880,6 +880,9 @@ 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;
+
error = inode_update_timestamps(inode, &flags);
if (error || !flags)
return error;
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 7f631473da6c..33af8bbeab4f 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 eddb2bab0edd..924ea0449dc6 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 << 3,
+
+ S_NOWAIT = 1U << 15,
};
extern bool atime_needs_update(const struct path *, struct inode *);
--
2.47.3
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