| Message ID | 20150720170109.GA3909@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Mon 20-07-15 19:01:09, Oleg Nesterov wrote: > Change thaw_super() to re-acquire the "write" locks we are going to > release. This way s_op->unfreeze_fs(sb) is called with these locks > held as it seen by lockdep, and this matches the reality. This adds > another trivial helper, sb_freeze_acquire(). > > Signed-off-by: Oleg Nesterov <oleg@redhat.com> Ah, I was confused for a moment why this doesn't trigger a lockdep warning because of lock inversion between s_umount and freeze protection but you use trylock in sb_freeze_acquire(). So things are fine. You can add: Reviewed-by: Jan Kara <jack@suse.com> Honza > --- > fs/super.c | 12 ++++++++++++ > 1 files changed, 12 insertions(+), 0 deletions(-) > > diff --git a/fs/super.c b/fs/super.c > index e7ea9f1..b4db3ee 100644 > --- a/fs/super.c > +++ b/fs/super.c > @@ -1263,6 +1263,14 @@ static void sb_freeze_release(struct super_block *sb) > rwsem_release(sb->s_writers.lock_map + level, 1, _THIS_IP_); > } > > +static void sb_freeze_acquire(struct super_block *sb) > +{ > + int level; > + > + for (level = 0; level < SB_FREEZE_LEVELS; ++level) > + rwsem_acquire(sb->s_writers.lock_map + level, 0, 1, _THIS_IP_); > +} > + > /** > * freeze_super - lock the filesystem and force it into a consistent state > * @sb: the super to lock > @@ -1386,16 +1394,20 @@ int thaw_super(struct super_block *sb) > if (sb->s_flags & MS_RDONLY) > goto out; > > + sb_freeze_acquire(sb); > + > if (sb->s_op->unfreeze_fs) { > error = sb->s_op->unfreeze_fs(sb); > if (error) { > printk(KERN_ERR > "VFS:Filesystem thaw failed\n"); > + sb_freeze_release(sb); > up_write(&sb->s_umount); > return error; > } > } > > + sb_freeze_release(sb); > out: > sb->s_writers.frozen = SB_UNFROZEN; > smp_wmb(); > -- > 1.5.5.1 >
diff --git a/fs/super.c b/fs/super.c index e7ea9f1..b4db3ee 100644 --- a/fs/super.c +++ b/fs/super.c @@ -1263,6 +1263,14 @@ static void sb_freeze_release(struct super_block *sb) rwsem_release(sb->s_writers.lock_map + level, 1, _THIS_IP_); } +static void sb_freeze_acquire(struct super_block *sb) +{ + int level; + + for (level = 0; level < SB_FREEZE_LEVELS; ++level) + rwsem_acquire(sb->s_writers.lock_map + level, 0, 1, _THIS_IP_); +} + /** * freeze_super - lock the filesystem and force it into a consistent state * @sb: the super to lock @@ -1386,16 +1394,20 @@ int thaw_super(struct super_block *sb) if (sb->s_flags & MS_RDONLY) goto out; + sb_freeze_acquire(sb); + if (sb->s_op->unfreeze_fs) { error = sb->s_op->unfreeze_fs(sb); if (error) { printk(KERN_ERR "VFS:Filesystem thaw failed\n"); + sb_freeze_release(sb); up_write(&sb->s_umount); return error; } } + sb_freeze_release(sb); out: sb->s_writers.frozen = SB_UNFROZEN; smp_wmb();
Change thaw_super() to re-acquire the "write" locks we are going to release. This way s_op->unfreeze_fs(sb) is called with these locks held as it seen by lockdep, and this matches the reality. This adds another trivial helper, sb_freeze_acquire(). Signed-off-by: Oleg Nesterov <oleg@redhat.com> --- fs/super.c | 12 ++++++++++++ 1 files changed, 12 insertions(+), 0 deletions(-)