The patch titled
vfs: allow mnt_want_write() to sleep
has been added to the -mm tree. Its filename is
vfs-allow-mnt_want_write-to-sleep.patch
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/SubmitChecklist when testing your code ***
See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find
out what to do about this
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: vfs: allow mnt_want_write() to sleep
From: Miklos Szeredi <mszeredi@xxxxxxx>
Allow mnt_want_write() to sleep.
This is necessary to enable holding off write requests for the duration of
->remount_fs(), which may sleep.
A quick audit didn't turn up any callers from atomic context.
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/namespace.c | 11 +++++++----
fs/super.c | 1 +
include/linux/fs.h | 5 +++++
3 files changed, 13 insertions(+), 4 deletions(-)
diff -puN fs/namespace.c~vfs-allow-mnt_want_write-to-sleep fs/namespace.c
--- a/fs/namespace.c~vfs-allow-mnt_want_write-to-sleep
+++ a/fs/namespace.c
@@ -281,8 +281,12 @@ int mnt_want_write(struct vfsmount *mnt)
* incremented count after it has set MNT_WRITE_HOLD.
*/
smp_mb();
- while (mnt->mnt_flags & MNT_WRITE_HOLD)
- cpu_relax();
+ if (unlikely(mnt->mnt_flags & MNT_WRITE_HOLD)) {
+ preempt_enable();
+ wait_event(mnt->mnt_sb->s_wait_remount_readonly,
+ !(mnt->mnt_flags & MNT_WRITE_HOLD));
+ preempt_disable();
+ }
/*
* After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will
* be set to match its requirements. So we must not load that until
@@ -292,9 +296,7 @@ int mnt_want_write(struct vfsmount *mnt)
if (__mnt_is_readonly(mnt)) {
dec_mnt_writers(mnt);
ret = -EROFS;
- goto out;
}
-out:
preempt_enable();
return ret;
}
@@ -395,6 +397,7 @@ static int mnt_make_readonly(struct vfsm
*/
smp_wmb();
mnt->mnt_flags &= ~MNT_WRITE_HOLD;
+ wake_up_all(&mnt->mnt_sb->s_wait_remount_readonly);
br_write_unlock(vfsmount_lock);
return ret;
}
diff -puN fs/super.c~vfs-allow-mnt_want_write-to-sleep fs/super.c
--- a/fs/super.c~vfs-allow-mnt_want_write-to-sleep
+++ a/fs/super.c
@@ -108,6 +108,7 @@ static struct super_block *alloc_super(s
mutex_init(&s->s_dquot.dqonoff_mutex);
init_rwsem(&s->s_dquot.dqptr_sem);
init_waitqueue_head(&s->s_wait_unfrozen);
+ init_waitqueue_head(&s->s_wait_remount_readonly);
s->s_maxbytes = MAX_NON_LFS;
s->s_op = &default_op;
s->s_time_gran = 1000000000;
diff -puN include/linux/fs.h~vfs-allow-mnt_want_write-to-sleep include/linux/fs.h
--- a/include/linux/fs.h~vfs-allow-mnt_want_write-to-sleep
+++ a/include/linux/fs.h
@@ -1380,6 +1380,11 @@ struct super_block {
struct mutex s_vfs_rename_mutex; /* Kludge */
/*
+ * Wait queue for remouting read-only
+ */
+ wait_queue_head_t s_wait_remount_readonly;
+
+ /*
* Filesystem subtype. If non-empty the filesystem type field
* in /proc/mounts will be "type.subtype"
*/
_
Patches currently in -mm which might be from mszeredi@xxxxxxx are
linux-next.patch
vfs-fix-infinite-loop-caused-by-clone_mnt-race.patch
vfs-ignore-error-on-forced-remount.patch
vfs-fix-per-mount-read-write.patch
vfs-add-sb_force_remount_readonly-helper.patch
vfs-allow-mnt_want_write-to-sleep.patch
vfs-allow-mnt_want_write-to-sleep-fix.patch
vfs-keep-list-of-mounts-for-each-superblock.patch
vfs-protect-remounting-superblock-read-only.patch
vfs-fs_may_remount_ro-turn-unnecessary-check-into-a-warn_on.patch
vfs-mark-mounts-read-only-on-forced-remount.patch
fuse-use-clear_highpage-and-km_user0-instead-of-km_user1.patch
fuse-use-release_pages.patch
--
To unsubscribe from this list: send the line "unsubscribe mm-commits" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
