| From hch@lst.de Mon Jun 5 17:05:12 2017 |
| From: Christoph Hellwig <hch@lst.de> |
| Date: Sat, 3 Jun 2017 15:18:31 +0200 |
| Subject: xfs: xfs_trans_alloc_empty |
| To: stable@vger.kernel.org |
| Cc: linux-xfs@vger.kernel.org, "Darrick J . Wong" <darrick.wong@oracle.com> |
| Message-ID: <20170603131836.26661-21-hch@lst.de> |
| |
| From: Christoph Hellwig <hch@lst.de> |
| |
| This is a partial cherry-pick of commit e89c041338 |
| ("xfs: implement the GETFSMAP ioctl"), which also adds this helper, and |
| a great example of why feature patches should be properly split into |
| their parts. |
| |
| Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com> |
| [hch: split from the larger patch for -stable] |
| Signed-off-by: Christoph Hellwig <hch@lst.de> |
| --- |
| fs/xfs/xfs_trans.c | 22 ++++++++++++++++++++++ |
| fs/xfs/xfs_trans.h | 2 ++ |
| 2 files changed, 24 insertions(+) |
| |
| --- a/fs/xfs/xfs_trans.c |
| +++ b/fs/xfs/xfs_trans.c |
| @@ -263,6 +263,28 @@ xfs_trans_alloc( |
| } |
| |
| /* |
| + * Create an empty transaction with no reservation. This is a defensive |
| + * mechanism for routines that query metadata without actually modifying |
| + * them -- if the metadata being queried is somehow cross-linked (think a |
| + * btree block pointer that points higher in the tree), we risk deadlock. |
| + * However, blocks grabbed as part of a transaction can be re-grabbed. |
| + * The verifiers will notice the corrupt block and the operation will fail |
| + * back to userspace without deadlocking. |
| + * |
| + * Note the zero-length reservation; this transaction MUST be cancelled |
| + * without any dirty data. |
| + */ |
| +int |
| +xfs_trans_alloc_empty( |
| + struct xfs_mount *mp, |
| + struct xfs_trans **tpp) |
| +{ |
| + struct xfs_trans_res resv = {0}; |
| + |
| + return xfs_trans_alloc(mp, &resv, 0, 0, XFS_TRANS_NO_WRITECOUNT, tpp); |
| +} |
| + |
| +/* |
| * Record the indicated change to the given field for application |
| * to the file system's superblock when the transaction commits. |
| * For now, just store the change in the transaction structure. |
| --- a/fs/xfs/xfs_trans.h |
| +++ b/fs/xfs/xfs_trans.h |
| @@ -159,6 +159,8 @@ typedef struct xfs_trans { |
| int xfs_trans_alloc(struct xfs_mount *mp, struct xfs_trans_res *resp, |
| uint blocks, uint rtextents, uint flags, |
| struct xfs_trans **tpp); |
| +int xfs_trans_alloc_empty(struct xfs_mount *mp, |
| + struct xfs_trans **tpp); |
| void xfs_trans_mod_sb(xfs_trans_t *, uint, int64_t); |
| |
| struct xfs_buf *xfs_trans_get_buf_map(struct xfs_trans *tp, |