Re: [PATCH] Btrfs: fix race with freeze and free space inodes
On Sun, Sep 16, 2012 at 11:36:57PM -0600, Miao Xie wrote:
> On fri, 14 Sep 2012 11:26:20 -0400, Josef Bacik wrote:
> > So we start our freeze, somebody comes in and does an fsync() on a file
> > where we have to commit a transaction for whatever reason, and we will
> > deadlock because the freeze is waiting on FS_FREEZE people to stop writing
> > to the file system, but the transaction is waiting for its free space inodes
> > to be written out, which are in turn waiting on sb_start_intwrite while
> > trying to write the file extents. To fix this we'll just skip the
> > sb_start_intwrite() if we TRANS_JOIN_NOLOCK since we're being waited on by a
> > transaction commit so we're safe wrt to freeze and this will keep us from
> > deadlocking. Thanks,
> >
> > Signed-off-by: Josef Bacik
> > ---
> > fs/btrfs/transaction.c | 10 +-
> > 1 files changed, 9 insertions(+), 1 deletions(-)
> >
> > diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
> > index c9265a6..ba74dfb 100644
> > --- a/fs/btrfs/transaction.c
> > +++ b/fs/btrfs/transaction.c
> > @@ -342,7 +342,15 @@ again:
> > if (!h)
> > return ERR_PTR(-ENOMEM);
> >
> > - if (!__sb_start_write(root->fs_info->sb, SB_FREEZE_FS, false)) {
> > + /*
> > +* If we are JOIN_NOLOCK we're already committing a transaction and
> > +* waiting on this guy, so we don't need to do the sb_start_intwrite
> > +* because we're already holding a ref. We need this because we could
> > +* have raced in and did an fsync() on a file which can kick a commit
> > +* and then we deadlock with somebody doing a freeze.
> > +*/
> > + if (type != TRANS_JOIN_NOLOCK &&
> > + !__sb_start_write(root->fs_info->sb, SB_FREEZE_FS, false)) {
> > if (type == TRANS_JOIN_FREEZE)
> > return ERR_PTR(-EPERM);
> > sb_start_intwrite(root->fs_info->sb);
> >
>
> This patch forgets to deal with it in __btrfs_end_transaction(), or the
> freeze counter
> will be wrong.
>
This was fixed locally I just sent the wrong patch, thanks,
Josef
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH] Btrfs: fix race with freeze and free space inodes
On fri, 14 Sep 2012 11:26:20 -0400, Josef Bacik wrote:
> So we start our freeze, somebody comes in and does an fsync() on a file
> where we have to commit a transaction for whatever reason, and we will
> deadlock because the freeze is waiting on FS_FREEZE people to stop writing
> to the file system, but the transaction is waiting for its free space inodes
> to be written out, which are in turn waiting on sb_start_intwrite while
> trying to write the file extents. To fix this we'll just skip the
> sb_start_intwrite() if we TRANS_JOIN_NOLOCK since we're being waited on by a
> transaction commit so we're safe wrt to freeze and this will keep us from
> deadlocking. Thanks,
>
> Signed-off-by: Josef Bacik
> ---
> fs/btrfs/transaction.c | 10 +-
> 1 files changed, 9 insertions(+), 1 deletions(-)
>
> diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
> index c9265a6..ba74dfb 100644
> --- a/fs/btrfs/transaction.c
> +++ b/fs/btrfs/transaction.c
> @@ -342,7 +342,15 @@ again:
> if (!h)
> return ERR_PTR(-ENOMEM);
>
> - if (!__sb_start_write(root->fs_info->sb, SB_FREEZE_FS, false)) {
> + /*
> + * If we are JOIN_NOLOCK we're already committing a transaction and
> + * waiting on this guy, so we don't need to do the sb_start_intwrite
> + * because we're already holding a ref. We need this because we could
> + * have raced in and did an fsync() on a file which can kick a commit
> + * and then we deadlock with somebody doing a freeze.
> + */
> + if (type != TRANS_JOIN_NOLOCK &&
> + !__sb_start_write(root->fs_info->sb, SB_FREEZE_FS, false)) {
> if (type == TRANS_JOIN_FREEZE)
> return ERR_PTR(-EPERM);
> sb_start_intwrite(root->fs_info->sb);
>
This patch forgets to deal with it in __btrfs_end_transaction(), or the freeze
counter
will be wrong.
Thanks
Miao
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
[PATCH] Btrfs: fix race with freeze and free space inodes
So we start our freeze, somebody comes in and does an fsync() on a file
where we have to commit a transaction for whatever reason, and we will
deadlock because the freeze is waiting on FS_FREEZE people to stop writing
to the file system, but the transaction is waiting for its free space inodes
to be written out, which are in turn waiting on sb_start_intwrite while
trying to write the file extents. To fix this we'll just skip the
sb_start_intwrite() if we TRANS_JOIN_NOLOCK since we're being waited on by a
transaction commit so we're safe wrt to freeze and this will keep us from
deadlocking. Thanks,
Signed-off-by: Josef Bacik
---
fs/btrfs/transaction.c | 10 +-
1 files changed, 9 insertions(+), 1 deletions(-)
diff --git a/fs/btrfs/transaction.c b/fs/btrfs/transaction.c
index c9265a6..ba74dfb 100644
--- a/fs/btrfs/transaction.c
+++ b/fs/btrfs/transaction.c
@@ -342,7 +342,15 @@ again:
if (!h)
return ERR_PTR(-ENOMEM);
- if (!__sb_start_write(root->fs_info->sb, SB_FREEZE_FS, false)) {
+ /*
+* If we are JOIN_NOLOCK we're already committing a transaction and
+* waiting on this guy, so we don't need to do the sb_start_intwrite
+* because we're already holding a ref. We need this because we could
+* have raced in and did an fsync() on a file which can kick a commit
+* and then we deadlock with somebody doing a freeze.
+*/
+ if (type != TRANS_JOIN_NOLOCK &&
+ !__sb_start_write(root->fs_info->sb, SB_FREEZE_FS, false)) {
if (type == TRANS_JOIN_FREEZE)
return ERR_PTR(-EPERM);
sb_start_intwrite(root->fs_info->sb);
--
1.7.7.6
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
