| Message ID | 1347636380-30185-1-git-send-email-jbacik@fusionio.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
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 <jbacik@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. Thanks Miao -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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 <jbacik@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 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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);
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 <jbacik@fusionio.com> --- fs/btrfs/transaction.c | 10 +++++++++- 1 files changed, 9 insertions(+), 1 deletions(-)