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>
---
fs/namespace.c | 11 +++++++----
fs/super.c | 1 +
include/linux/fs.h | 5 +++++
3 files changed, 13 insertions(+), 4 deletions(-)
Index: linux-2.6/fs/namespace.c
===================================================================
--- linux-2.6.orig/fs/namespace.c 2010-10-04 12:15:17.000000000 +0200
+++ linux-2.6/fs/namespace.c 2010-10-04 16:50:44.000000000 +0200
@@ -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;
}
Index: linux-2.6/fs/super.c
===================================================================
--- linux-2.6.orig/fs/super.c 2010-10-04 12:12:01.000000000 +0200
+++ linux-2.6/fs/super.c 2010-10-04 16:50:25.000000000 +0200
@@ -107,6 +107,7 @@ 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;
Index: linux-2.6/include/linux/fs.h
===================================================================
--- linux-2.6.orig/include/linux/fs.h 2010-10-04 12:13:00.000000000 +0200
+++ linux-2.6/include/linux/fs.h 2010-10-04 16:50:25.000000000 +0200
@@ -1385,6 +1385,11 @@ struct super_block {
* generic_show_options()
*/
char *s_options;
+
+ /*
+ * Wait queue for remouting read-only
+ */
+ wait_queue_head_t s_wait_remount_readonly;
};
extern struct timespec current_fs_time(struct super_block *sb);
--
--
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