diff options
| author | Christoph Hellwig <hch@lst.de> | 2017-06-03 15:18:31 +0200 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2017-06-07 12:07:52 +0200 |
| commit | e40c145c023db15a0504e95ac442f0e47c0a816d (patch) | |
| tree | 0bec11fba02c7f976c55f05d0b9752d465bb39dd | |
| parent | 0e542792a046c788f39ab13fcd68c7ba65930407 (diff) | |
xfs: xfs_trans_alloc_empty
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>
| -rw-r--r-- | fs/xfs/xfs_trans.c | 22 | ||||
| -rw-r--r-- | fs/xfs/xfs_trans.h | 2 |
2 files changed, 24 insertions, 0 deletions
diff --git a/fs/xfs/xfs_trans.c b/fs/xfs/xfs_trans.c index 70f42ea86dfb..a280e126491f 100644 --- 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. diff --git a/fs/xfs/xfs_trans.h b/fs/xfs/xfs_trans.h index 61b7fbdd3ebd..98024cb933ef 100644 --- 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, |