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fs/9p: don't set SB_NOATIME by default

PATCH In review jiangyiwen 2 participants 3 messages Mar 27, 2018 – Mar 28, 2018 9P file system

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jiangyiwen

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#0 lore raw

PATCH 1/1 fs/9p: don't set SB_NOATIME by default

User use some syscall, for example mmap(v9fs_file_mmap), it will not update atime even if user's mnt_flags without MNT_NOATIME, because v9fs default set SB_NOATIME in v9fs_set_super.

For supporting access time is updated when user mount with relatime, we should not set SB_NOATIME by default.

Signed-off-by Yiwen Jiang <[email protected]>
Reviewed-by Greg Kurz <[email protected]>
---
 fs/9p/vfs_super.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
fs/9p/vfs_super.c +1 -1
index af03c2a..48ce504 100644
@@ -94,7 +94,7 @@ static int v9fs_set_super(struct super_block *s, void *data)
 	if (v9ses->cache)
 		sb->s_bdi->ra_pages = (VM_MAX_READAHEAD * 1024)/PAGE_SIZE;
 
-	sb->s_flags |= SB_ACTIVE | SB_DIRSYNC | SB_NOATIME;
+	sb->s_flags |= SB_ACTIVE | SB_DIRSYNC;
 	if (!v9ses->cache)
 		sb->s_flags |= SB_SYNCHRONOUS;
Signature · 1 line
1.8.3.1
#1 lore raw
Quoted 12 lines · On Tue, 27 Mar 2018 09:50:47 +0800 jiangyiwen <[email protected]> wrote:

User use some syscall, for example mmap(v9fs_file_mmap), it will not update atime even if user's mnt_flags without MNT_NOATIME, because v9fs default set SB_NOATIME in v9fs_set_super.

For supporting access time is updated when user mount with relatime, we should not set SB_NOATIME by default.

...

fs/9p/vfs_super.c static int v9fs_set_super(struct super_block *s, void *data) · line 100

Quoted 8 lines
fs/9p/vfs_super.c +1 -1
@@ -94,7 +94,7 @@ static int v9fs_set_super(struct super_block *s, void *data)
 	if (v9ses->cache)
 		sb->s_bdi->ra_pages = (VM_MAX_READAHEAD * 1024)/PAGE_SIZE;
 
-	sb->s_flags |= SB_ACTIVE | SB_DIRSYNC | SB_NOATIME;
+	sb->s_flags |= SB_ACTIVE | SB_DIRSYNC;
 	if (!v9ses->cache)
 		sb->s_flags |= SB_SYNCHRONOUS;

So strictly speaking, this is a non-backward-compatible change, yes?

Please describe the circumstances under which an existing user might be harmed by this. I *think* such harm will occur if the user was already using 'mount -o relatime', yes? They previously weren't getting relatime treatment, but now they will, and things will be a little slower.

If correct, that sounds acceptable.

author
#2 lore raw
Quoted 25 lines · Andrew Morton
Quoted 12 lines · On Tue, 27 Mar 2018 09:50:47 +0800 jiangyiwen <[email protected]> wrote:

User use some syscall, for example mmap(v9fs_file_mmap), it will not update atime even if user's mnt_flags without MNT_NOATIME, because v9fs default set SB_NOATIME in v9fs_set_super.

For supporting access time is updated when user mount with relatime, we should not set SB_NOATIME by default.

...

fs/9p/vfs_super.c static int v9fs_set_super(struct super_block *s, void *data) · line 100

Quoted 8 lines
fs/9p/vfs_super.c +1 -1
@@ -94,7 +94,7 @@ static int v9fs_set_super(struct super_block *s, void *data)
 	if (v9ses->cache)
 		sb->s_bdi->ra_pages = (VM_MAX_READAHEAD * 1024)/PAGE_SIZE;
 
-	sb->s_flags |= SB_ACTIVE | SB_DIRSYNC | SB_NOATIME;
+	sb->s_flags |= SB_ACTIVE | SB_DIRSYNC;
 	if (!v9ses->cache)
 		sb->s_flags |= SB_SYNCHRONOUS;

So strictly speaking, this is a non-backward-compatible change, yes?

Quoted 5 lines

Please describe the circumstances under which an existing user might be harmed by this. I *think* such harm will occur if the user was already using 'mount -o relatime', yes? They previously weren't getting relatime treatment, but now they will, and things will be a little slower.

Yes, after using this change, if user was already using 'mount -o relatime', their atime will be changed, and some operations will result in slower performance, but I think user should use 'noatime' option if they hope their file's atime is not updated and user should not depend on the internal implement.

Quoted 4 lines

If correct, that sounds acceptable.

.