From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-xfs@vger.kernel.org,
"Darrick J . Wong" <darrick.wong@oracle.com>,
Christoph Hellwig <hch@lst.de>
Subject: [PATCH 4.11 112/115] xfs: xfs_trans_alloc_empty
Date: Mon, 5 Jun 2017 18:18:25 +0200 [thread overview]
Message-ID: <20170605153102.219732457@linuxfoundation.org> (raw)
In-Reply-To: <20170605153056.650217313@linuxfoundation.org>
4.11-stable review patch. If anyone has any objections, please let me know.
------------------
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
@@ -158,6 +158,8 @@ 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,
parent reply other threads:[~2017-06-05 16:33 UTC|newest]
Thread overview: expand[flat|nested] mbox.gz Atom feed
[parent not found: <20170605153056.650217313@linuxfoundation.org>]
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