Commit ecb42615 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Greg Kroah-Hartman

xfs: xfs_trans_alloc_empty

This is a partial cherry-pick of commit e89c0413
("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: default avatarDarrick J. Wong <darrick.wong@oracle.com>
[hch: split from the larger patch for -stable]
Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
parent 2e08bd63
...@@ -262,6 +262,28 @@ xfs_trans_alloc( ...@@ -262,6 +262,28 @@ xfs_trans_alloc(
return 0; return 0;
} }
/*
* 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 * Record the indicated change to the given field for application
* to the file system's superblock when the transaction commits. * to the file system's superblock when the transaction commits.
......
...@@ -158,6 +158,8 @@ typedef struct xfs_trans { ...@@ -158,6 +158,8 @@ typedef struct xfs_trans {
int xfs_trans_alloc(struct xfs_mount *mp, struct xfs_trans_res *resp, int xfs_trans_alloc(struct xfs_mount *mp, struct xfs_trans_res *resp,
uint blocks, uint rtextents, uint flags, uint blocks, uint rtextents, uint flags,
struct xfs_trans **tpp); 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); void xfs_trans_mod_sb(xfs_trans_t *, uint, int64_t);
struct xfs_buf *xfs_trans_get_buf_map(struct xfs_trans *tp, struct xfs_buf *xfs_trans_get_buf_map(struct xfs_trans *tp,
......
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