release 6.15.2 (preliminary)

debian/patches/patchset-pf/xfs/0001-xfs-don-t-assume-perags-are-initialised-when-trimmin.patch

@@ -0,0 +1,81 @@
+From c63d4a0865e8e7549e1305cc67b88a355a4a9a02 Mon Sep 17 00:00:00 2001
+From: Dave Chinner <dchinner@redhat.com>
+Date: Thu, 1 May 2025 09:27:24 +1000
+Subject: xfs: don't assume perags are initialised when trimming AGs
+
+When running fstrim immediately after mounting a V4 filesystem,
+the fstrim fails to trim all the free space in the filesystem. It
+only trims the first extent in the by-size free space tree in each
+AG and then returns. If a second fstrim is then run, it runs
+correctly and the entire free space in the filesystem is iterated
+and discarded correctly.
+
+The problem lies in the setup of the trim cursor - it assumes that
+pag->pagf_longest is valid without either reading the AGF first or
+checking if xfs_perag_initialised_agf(pag) is true or not.
+
+As a result, when a filesystem is mounted without reading the AGF
+(e.g. a clean mount on a v4 filesystem) and the first operation is a
+fstrim call, pag->pagf_longest is zero and so the free extent search
+starts at the wrong end of the by-size btree and exits after
+discarding the first record in the tree.
+
+Fix this by deferring the initialisation of tcur->count to after
+we have locked the AGF and guaranteed that the perag is properly
+initialised. We trigger this on tcur->count == 0 after locking the
+AGF, as this will only occur on the first call to
+xfs_trim_gather_extents() for each AG. If we need to iterate,
+tcur->count will be set to the length of the record we need to
+restart at, so we can use this to ensure we only sample a valid
+pag->pagf_longest value for the iteration.
+
+Signed-off-by: Dave Chinner <dchinner@redhat.com>
+Reviewed-by: Bill O'Donnell <bodonnel@redhat.com>
+Reviewed-by: Darrick J. Wong <djwong@kernel.org>
+Fixes: 89cfa899608f ("xfs: reduce AGF hold times during fstrim operations")
+Cc: <stable@vger.kernel.org> # v6.6
+Signed-off-by: Carlos Maiolino <cem@kernel.org>
+---
+ fs/xfs/xfs_discard.c | 17 ++++++++++++++++-
+ 1 file changed, 16 insertions(+), 1 deletion(-)
+
+--- a/fs/xfs/xfs_discard.c
++++ b/fs/xfs/xfs_discard.c
+@@ -167,6 +167,14 @@ xfs_discard_extents(
+ 	return error;
+ }
+ 
++/*
++ * Care must be taken setting up the trim cursor as the perags may not have been
++ * initialised when the cursor is initialised. e.g. a clean mount which hasn't
++ * read in AGFs and the first operation run on the mounted fs is a trim. This
++ * can result in perag fields that aren't initialised until
++ * xfs_trim_gather_extents() calls xfs_alloc_read_agf() to lock down the AG for
++ * the free space search.
++ */
+ struct xfs_trim_cur {
+ 	xfs_agblock_t	start;
+ 	xfs_extlen_t	count;
+@@ -204,6 +212,14 @@ xfs_trim_gather_extents(
+ 	if (error)
+ 		goto out_trans_cancel;
+ 
++	/*
++	 * First time through tcur->count will not have been initialised as
++	 * pag->pagf_longest is not guaranteed to be valid before we read
++	 * the AGF buffer above.
++	 */
++	if (!tcur->count)
++		tcur->count = pag->pagf_longest;
++
+ 	if (tcur->by_bno) {
+ 		/* sub-AG discard request always starts at tcur->start */
+ 		cur = xfs_bnobt_init_cursor(mp, tp, agbp, pag);
+@@ -350,7 +366,6 @@ xfs_trim_perag_extents(
+ {
+ 	struct xfs_trim_cur	tcur = {
+ 		.start		= start,
+-		.count		= pag->pagf_longest,
+ 		.end		= end,
+ 		.minlen		= minlen,
+ 	};