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 <jba...@fusionio.com>
> > ---
> > 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
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