This is a note to let you know that I've just added the patch titled
xfs: xfs_trans_alloc_empty
to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
xfs-xfs_trans_alloc_empty.patch
and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From hch@xxxxxx Mon Jun 5 17:05:12 2017
From: Christoph Hellwig <hch@xxxxxx>
Date: Sat, 3 Jun 2017 15:18:31 +0200
Subject: xfs: xfs_trans_alloc_empty
To: stable@xxxxxxxxxxxxxxx
Cc: linux-xfs@xxxxxxxxxxxxxxx, "Darrick J . Wong" <darrick.wong@xxxxxxxxxx>
Message-ID: <20170603131836.26661-21-hch@xxxxxx>
From: Christoph Hellwig <hch@xxxxxx>
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@xxxxxxxxxx>
[hch: split from the larger patch for -stable]
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
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,
Patches currently in stable-queue which might be from hch@xxxxxx are
queue-4.9/nvme-use-blk_mq_start_hw_queues-in-nvme_kill_queues.patch
queue-4.9/xfs-fix-over-copying-of-getbmap-parameters-from-userspace.patch
queue-4.9/xfs-bmapx-shouldn-t-barf-on-inline-format-directories.patch
queue-4.9/nvme-avoid-to-use-blk_mq_abort_requeue_list.patch
queue-4.9/xfs-rework-the-inline-directory-verifiers.patch
queue-4.9/nvme-rdma-support-devices-with-queue-size-32.patch
queue-4.9/xfs-xfs_trans_alloc_empty.patch
queue-4.9/xfs-fix-integer-truncation-in-xfs_bmap_remap_alloc.patch
queue-4.9/xfs-actually-report-xattr-extents-via-iomap.patch
queue-4.9/xfs-fix-use-after-free-in-xfs_finish_page_writeback.patch
queue-4.9/xfs-reserve-enough-blocks-to-handle-btree-splits-when-remapping.patch
queue-4.9/xfs-fix-kernel-memory-exposure-problems.patch