[PATCH] mount: warn only once about timestamp range expiration

[Anthony Iliopoulos]

Commit f8b92ba67c5d ("mount: Add mount warning for impending timestamp
expiry") introduced a mount warning regarding filesystem timestamp
limits, that is printed upon each writable mount or remount.

This can result in a lot of unnecessary messages in the kernel log in
setups where filesystems are being frequently remounted (or mounted
multiple times).

Avoid this by setting a superblock flag which indicates that the warning
has been emitted at least once for any particular mount, as suggested in
[1].

Signed-off-by: Anthony Iliopoulos <ailiop@xxxxxxxx>

[1] https://lore.kernel.org/CAHk-=wim6VGnxQmjfK_tDg6fbHYKL4EFkmnTjVr9QnRqjDBAeA@xxxxxxxxxxxxxx/
---
 fs/namespace.c     | 2 ++
 include/linux/fs.h | 1 +
 2 files changed, 3 insertions(+)

diff --git a/fs/namespace.c b/fs/namespace.c
index 659a8f39c61a..21deeefe0af1 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2561,6 +2561,7 @@ static void mnt_warn_timestamp_expiry(struct path *mountpoint, struct vfsmount *
 	struct super_block *sb = mnt->mnt_sb;
 
 	if (!__mnt_is_readonly(mnt) &&
+	   (!(sb->s_iflags & SB_I_TS_EXPIRY_WARNED)) &&
 	   (ktime_get_real_seconds() + TIME_UPTIME_SEC_MAX > sb->s_time_max)) {
 		char *buf = (char *)__get_free_page(GFP_KERNEL);
 		char *mntpath = buf ? d_path(mountpoint, buf, PAGE_SIZE) : ERR_PTR(-ENOMEM);
@@ -2575,6 +2576,7 @@ static void mnt_warn_timestamp_expiry(struct path *mountpoint, struct vfsmount *
 			tm.tm_year+1900, (unsigned long long)sb->s_time_max);
 
 		free_page((unsigned long)buf);
+		sb->s_iflags |= SB_I_TS_EXPIRY_WARNED;
 	}
 }
 
diff --git a/include/linux/fs.h b/include/linux/fs.h
index bbf812ce89a8..21cbb1812196 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1441,6 +1441,7 @@ extern int send_sigurg(struct fown_struct *fown);
 
 #define SB_I_SKIP_SYNC	0x00000100	/* Skip superblock at global sync */
 #define SB_I_PERSB_BDI	0x00000200	/* has a per-sb bdi */
+#define SB_I_TS_EXPIRY_WARNED 0x00000400 /* warned about timestamp range expiry */
 
 /* Possible states of 'frozen' field */
 enum {
-- 
2.34.1