--- /dev/null
+From e836007089ba8fdf24e636ef2b007651fb4582e6 Mon Sep 17 00:00:00 2001
+From: Jason Baron <jbaron@akamai.com>
+Date: Fri, 23 Jun 2023 14:05:23 -0400
+Subject: md/raid0: add discard support for the 'original' layout
+
+From: Jason Baron <jbaron@akamai.com>
+
+commit e836007089ba8fdf24e636ef2b007651fb4582e6 upstream.
+
+We've found that using raid0 with the 'original' layout and discard
+enabled with different disk sizes (such that at least two zones are
+created) can result in data corruption. This is due to the fact that
+the discard handling in 'raid0_handle_discard()' assumes the 'alternate'
+layout. We've seen this corruption using ext4 but other filesystems are
+likely susceptible as well.
+
+More specifically, while multiple zones are necessary to create the
+corruption, the corruption may not occur with multiple zones if they
+layout in such a way the layout matches what the 'alternate' layout
+would have produced. Thus, not all raid0 devices with the 'original'
+layout, different size disks and discard enabled will encounter this
+corruption.
+
+The 3.14 kernel inadvertently changed the raid0 disk layout for different
+size disks. Thus, running a pre-3.14 kernel and post-3.14 kernel on the
+same raid0 array could corrupt data. This lead to the creation of the
+'original' layout (to match the pre-3.14 layout) and the 'alternate' layout
+(to match the post 3.14 layout) in the 5.4 kernel time frame and an option
+to tell the kernel which layout to use (since it couldn't be autodetected).
+However, when the 'original' layout was added back to 5.4 discard support
+for the 'original' layout was not added leading this issue.
+
+I've been able to reliably reproduce the corruption with the following
+test case:
+
+1. create raid0 array with different size disks using original layout
+2. mkfs
+3. mount -o discard
+4. create lots of files
+5. remove 1/2 the files
+6. fstrim -a (or just the mount point for the raid0 array)
+7. umount
+8. fsck -fn /dev/md0 (spews all sorts of corruptions)
+
+Let's fix this by adding proper discard support to the 'original' layout.
+The fix 'maps' the 'original' layout disks to the order in which they are
+read/written such that we can compare the disks in the same way that the
+current 'alternate' layout does. A 'disk_shift' field is added to
+'struct strip_zone'. This could be computed on the fly in
+raid0_handle_discard() but by adding this field, we save some computation
+in the discard path.
+
+Note we could also potentially fix this by re-ordering the disks in the
+zones that follow the first one, and then always read/writing them using
+the 'alternate' layout. However, that is seen as a more substantial change,
+and we are attempting the least invasive fix at this time to remedy the
+corruption.
+
+I've verified the change using the reproducer mentioned above. Typically,
+the corruption is seen after less than 3 iterations, while the patch has
+run 500+ iterations.
+
+Cc: NeilBrown <neilb@suse.de>
+Cc: Song Liu <song@kernel.org>
+Fixes: c84a1372df92 ("md/raid0: avoid RAID0 data corruption due to layout confusion.")
+Cc: stable@vger.kernel.org
+Signed-off-by: Jason Baron <jbaron@akamai.com>
+Signed-off-by: Song Liu <song@kernel.org>
+Link: https://lore.kernel.org/r/20230623180523.1901230-1-jbaron@akamai.com
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+---
+ drivers/md/raid0.c | 62 ++++++++++++++++++++++++++++++++++++++++++++++-------
+ drivers/md/raid0.h | 1
+ 2 files changed, 55 insertions(+), 8 deletions(-)
+
+--- a/drivers/md/raid0.c
++++ b/drivers/md/raid0.c
+@@ -296,6 +296,18 @@ static int create_strip_zones(struct mdd
+ goto abort;
+ }
+
++ if (conf->layout == RAID0_ORIG_LAYOUT) {
++ for (i = 1; i < conf->nr_strip_zones; i++) {
++ sector_t first_sector = conf->strip_zone[i-1].zone_end;
++
++ sector_div(first_sector, mddev->chunk_sectors);
++ zone = conf->strip_zone + i;
++ /* disk_shift is first disk index used in the zone */
++ zone->disk_shift = sector_div(first_sector,
++ zone->nb_dev);
++ }
++ }
++
+ pr_debug("md/raid0:%s: done.\n", mdname(mddev));
+ *private_conf = conf;
+
+@@ -482,6 +494,20 @@ static inline int is_io_in_chunk_boundar
+ }
+ }
+
++/*
++ * Convert disk_index to the disk order in which it is read/written.
++ * For example, if we have 4 disks, they are numbered 0,1,2,3. If we
++ * write the disks starting at disk 3, then the read/write order would
++ * be disk 3, then 0, then 1, and then disk 2 and we want map_disk_shift()
++ * to map the disks as follows 0,1,2,3 => 1,2,3,0. So disk 0 would map
++ * to 1, 1 to 2, 2 to 3, and 3 to 0. That way we can compare disks in
++ * that 'output' space to understand the read/write disk ordering.
++ */
++static int map_disk_shift(int disk_index, int num_disks, int disk_shift)
++{
++ return ((disk_index + num_disks - disk_shift) % num_disks);
++}
++
+ static void raid0_handle_discard(struct mddev *mddev, struct bio *bio)
+ {
+ struct r0conf *conf = mddev->private;
+@@ -495,7 +521,9 @@ static void raid0_handle_discard(struct
+ sector_t end_disk_offset;
+ unsigned int end_disk_index;
+ unsigned int disk;
++ sector_t orig_start, orig_end;
+
++ orig_start = start;
+ zone = find_zone(conf, &start);
+
+ if (bio_end_sector(bio) > zone->zone_end) {
+@@ -509,6 +537,7 @@ static void raid0_handle_discard(struct
+ } else
+ end = bio_end_sector(bio);
+
++ orig_end = end;
+ if (zone != conf->strip_zone)
+ end = end - zone[-1].zone_end;
+
+@@ -520,13 +549,26 @@ static void raid0_handle_discard(struct
+ last_stripe_index = end;
+ sector_div(last_stripe_index, stripe_size);
+
+- start_disk_index = (int)(start - first_stripe_index * stripe_size) /
+- mddev->chunk_sectors;
++ /* In the first zone the original and alternate layouts are the same */
++ if ((conf->layout == RAID0_ORIG_LAYOUT) && (zone != conf->strip_zone)) {
++ sector_div(orig_start, mddev->chunk_sectors);
++ start_disk_index = sector_div(orig_start, zone->nb_dev);
++ start_disk_index = map_disk_shift(start_disk_index,
++ zone->nb_dev,
++ zone->disk_shift);
++ sector_div(orig_end, mddev->chunk_sectors);
++ end_disk_index = sector_div(orig_end, zone->nb_dev);
++ end_disk_index = map_disk_shift(end_disk_index,
++ zone->nb_dev, zone->disk_shift);
++ } else {
++ start_disk_index = (int)(start - first_stripe_index * stripe_size) /
++ mddev->chunk_sectors;
++ end_disk_index = (int)(end - last_stripe_index * stripe_size) /
++ mddev->chunk_sectors;
++ }
+ start_disk_offset = ((int)(start - first_stripe_index * stripe_size) %
+ mddev->chunk_sectors) +
+ first_stripe_index * mddev->chunk_sectors;
+- end_disk_index = (int)(end - last_stripe_index * stripe_size) /
+- mddev->chunk_sectors;
+ end_disk_offset = ((int)(end - last_stripe_index * stripe_size) %
+ mddev->chunk_sectors) +
+ last_stripe_index * mddev->chunk_sectors;
+@@ -535,18 +577,22 @@ static void raid0_handle_discard(struct
+ sector_t dev_start, dev_end;
+ struct bio *discard_bio = NULL;
+ struct md_rdev *rdev;
++ int compare_disk;
++
++ compare_disk = map_disk_shift(disk, zone->nb_dev,
++ zone->disk_shift);
+
+- if (disk < start_disk_index)
++ if (compare_disk < start_disk_index)
+ dev_start = (first_stripe_index + 1) *
+ mddev->chunk_sectors;
+- else if (disk > start_disk_index)
++ else if (compare_disk > start_disk_index)
+ dev_start = first_stripe_index * mddev->chunk_sectors;
+ else
+ dev_start = start_disk_offset;
+
+- if (disk < end_disk_index)
++ if (compare_disk < end_disk_index)
+ dev_end = (last_stripe_index + 1) * mddev->chunk_sectors;
+- else if (disk > end_disk_index)
++ else if (compare_disk > end_disk_index)
+ dev_end = last_stripe_index * mddev->chunk_sectors;
+ else
+ dev_end = end_disk_offset;
+--- a/drivers/md/raid0.h
++++ b/drivers/md/raid0.h
+@@ -6,6 +6,7 @@ struct strip_zone {
+ sector_t zone_end; /* Start of the next zone (in sectors) */
+ sector_t dev_start; /* Zone offset in real dev (in sectors) */
+ int nb_dev; /* # of devices attached to the zone */
++ int disk_shift; /* start disk for the original layout */
+ };
+
+ /* Linux 3.14 (20d0189b101) made an unintended change to
projects / thirdparty / kernel / stable-queue.git / commitdiff
