Patch "xfs: only update mount/resv fields on success in __xfs_ag_resv_init" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

xfs: only update mount/resv fields on success in __xfs_ag_resv_init

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-only-update-mount-resv-fields-on-success-in-__xfs_ag_resv_init.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 <[email protected]> know about it.

From: Christoph Hellwig <[email protected]>
Date: Wed, 25 Jan 2017 07:49:34 -0800
Subject: xfs: only update mount/resv fields on success in __xfs_ag_resv_init

From: Christoph Hellwig <[email protected]>

commit 4dfa2b84118fd6c95202ae87e62adf5000ccd4d0 upstream.

Try to reserve the blocks first and only then update the fields in or hanging off the mount structure. This way we can call __xfs_ag_resv_init again after a previous failure.

---
 fs/xfs/libxfs/xfs_ag_resv.c |   23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

@@ -200,22 +200,27 @@ __xfs_ag_resv_init(
 	struct xfs_mount		*mp = pag->pag_mount;
 	struct xfs_ag_resv		*resv;
 	int				error;
+	xfs_extlen_t			reserved;
 
-	resv = xfs_perag_resv(pag, type);
 	if (used > ask)
 		ask = used;
-	resv->ar_asked = ask;
-	resv->ar_reserved = resv->ar_orig_reserved = ask - used;
-	mp->m_ag_max_usable -= ask;
+	reserved = ask - used;
 
-	trace_xfs_ag_resv_init(pag, type, ask);
-
-	error = xfs_mod_fdblocks(mp, -(int64_t)resv->ar_reserved, true);
-	if (error)
+	error = xfs_mod_fdblocks(mp, -(int64_t)reserved, true);
+	if (error) {
 		trace_xfs_ag_resv_init_error(pag->pag_mount, pag->pag_agno,
 				error, _RET_IP_);
+		return error;
+	}
 
-	return error;
+	mp->m_ag_max_usable -= ask;
+
+	resv = xfs_perag_resv(pag, type);
+	resv->ar_asked = ask;
+	resv->ar_reserved = resv->ar_orig_reserved = reserved;
+
+	trace_xfs_ag_resv_init(pag, type, ask);
+	return 0;
 }
 
 /* Create a per-AG block reservation. */

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/xfs-sync-eofblocks-scans-under-iolock-are-livelock-prone.patch queue-4.9/xfs-use-per-ag-reservations-for-the-finobt.patch queue-4.9/xfs-pull-up-iolock-from-xfs_free_eofblocks.patch queue-4.9/xfs-only-update-mount-resv-fields-on-success-in-__xfs_ag_resv_init.patch