raid1: ensure write behind bio has less than BIO_MAX_VECS sectors

We can't split write behind bio with more than BIO_MAX_VECS sectors,
otherwise the below call trace was triggered because we could allocate
oversized write behind bio later.

[ 8.097936] bvec_alloc+0x90/0xc0
[ 8.098934] bio_alloc_bioset+0x1b3/0x260
[ 8.099959] raid1_make_request+0x9ce/0xc50 [raid1]
[ 8.100988] ? __bio_clone_fast+0xa8/0xe0
[ 8.102008] md_handle_request+0x158/0x1d0 [md_mod]
[ 8.103050] md_submit_bio+0xcd/0x110 [md_mod]
[ 8.104084] submit_bio_noacct+0x139/0x530
[ 8.105127] submit_bio+0x78/0x1d0
[ 8.106163] ext4_io_submit+0x48/0x60 [ext4]
[ 8.107242] ext4_writepages+0x652/0x1170 [ext4]
[ 8.108300] ? do_writepages+0x41/0x100
[ 8.109338] ? __ext4_mark_inode_dirty+0x240/0x240 [ext4]
[ 8.110406] do_writepages+0x41/0x100
[ 8.111450] __filemap_fdatawrite_range+0xc5/0x100
[ 8.112513] file_write_and_wait_range+0x61/0xb0
[ 8.113564] ext4_sync_file+0x73/0x370 [ext4]
[ 8.114607] __x64_sys_fsync+0x33/0x60
[ 8.115635] do_syscall_64+0x33/0x40
[ 8.116670] entry_SYSCALL_64_after_hwframe+0x44/0xae

Thanks for the comment from Christoph.

[1]. https://bugs.archlinux.org/task/70992

Cc: stable@vger.kernel.org # v5.12+
Reported-by: Jens Stutte <jens@chianterastutte.eu>
Tested-by: Jens Stutte <jens@chianterastutte.eu>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Guoqing Jiang <jiangguoqing@kylinos.cn>
Signed-off-by: Song Liu <songliubraving@fb.com>

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 51f2547..21b3484 100644 (file)
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -1331,6 +1331,7 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
        struct raid1_plug_cb *plug = NULL;
        int first_clone;
        int max_sectors;
+       bool write_behind = false;
 
        if (mddev_is_clustered(mddev) &&
             md_cluster_ops->area_resyncing(mddev, WRITE,
@@ -1383,6 +1384,15 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
        max_sectors = r1_bio->sectors;
        for (i = 0;  i < disks; i++) {
                struct md_rdev *rdev = rcu_dereference(conf->mirrors[i].rdev);
+
+               /*
+                * The write-behind io is only attempted on drives marked as
+                * write-mostly, which means we could allocate write behind
+                * bio later.
+                */
+               if (rdev && test_bit(WriteMostly, &rdev->flags))
+                       write_behind = true;
+
                if (rdev && unlikely(test_bit(Blocked, &rdev->flags))) {
                        atomic_inc(&rdev->nr_pending);
                        blocked_rdev = rdev;
@@ -1456,6 +1466,15 @@ static void raid1_write_request(struct mddev *mddev, struct bio *bio,
                goto retry_write;
        }
 
+       /*
+        * When using a bitmap, we may call alloc_behind_master_bio below.
+        * alloc_behind_master_bio allocates a copy of the data payload a page
+        * at a time and thus needs a new bio that can fit the whole payload
+        * this bio in page sized chunks.
+        */
+       if (write_behind && bitmap)
+               max_sectors = min_t(int, max_sectors,
+                                   BIO_MAX_VECS * (PAGE_SIZE >> 9));
        if (max_sectors < bio_sectors(bio)) {
                struct bio *split = bio_split(bio, max_sectors,
                                              GFP_NOIO, &conf->bio_split);