This is a note to let you know that I've just added the patch titled
btrfs: fix compressed writes that cross stripe boundary
to the 5.12-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:
btrfs-fix-compressed-writes-that-cross-stripe-bounda.patch
and it can be found in the queue-5.12 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit 6ac90347d410797dff70ea412aacb446f898b366
Author: Qu Wenruo <wqu@xxxxxxxx>
Date: Tue May 25 13:52:43 2021 +0800
btrfs: fix compressed writes that cross stripe boundary
[ Upstream commit 4c80a97d7b02cf68e169118ef2bda0725fc87f6f ]
[BUG]
When running btrfs/027 with "-o compress" mount option, it always
crashes with the following call trace:
BTRFS critical (device dm-4): mapping failed logical 298901504 bio len 12288 len 8192
------------[ cut here ]------------
kernel BUG at fs/btrfs/volumes.c:6651!
invalid opcode: 0000 [#1] PREEMPT SMP NOPTI
CPU: 5 PID: 31089 Comm: kworker/u24:10 Tainted: G OE 5.13.0-rc2-custom+ #26
Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015
Workqueue: btrfs-delalloc btrfs_work_helper [btrfs]
RIP: 0010:btrfs_map_bio.cold+0x58/0x5a [btrfs]
Call Trace:
btrfs_submit_compressed_write+0x2d7/0x470 [btrfs]
submit_compressed_extents+0x3b0/0x470 [btrfs]
? mark_held_locks+0x49/0x70
btrfs_work_helper+0x131/0x3e0 [btrfs]
process_one_work+0x28f/0x5d0
worker_thread+0x55/0x3c0
? process_one_work+0x5d0/0x5d0
kthread+0x141/0x160
? __kthread_bind_mask+0x60/0x60
ret_from_fork+0x22/0x30
---[ end trace 63113a3a91f34e68 ]---
[CAUSE]
The critical message before the crash means we have a bio at logical
bytenr 298901504 length 12288, but only 8192 bytes can fit into one
stripe, the remaining 4096 bytes go to another stripe.
In btrfs, all bios are properly split to avoid cross stripe boundary,
but commit 764c7c9a464b ("btrfs: zoned: fix parallel compressed writes")
changed the behavior for compressed writes.
Previously if we find our new page can't be fitted into current stripe,
ie. "submit == 1" case, we submit current bio without adding current
page.
submit = btrfs_bio_fits_in_stripe(page, PAGE_SIZE, bio, 0);
page->mapping = NULL;
if (submit || bio_add_page(bio, page, PAGE_SIZE, 0) <
PAGE_SIZE) {
But after the modification, we will add the page no matter if it crosses
stripe boundary, leading to the above crash.
submit = btrfs_bio_fits_in_stripe(page, PAGE_SIZE, bio, 0);
if (pg_index == 0 && use_append)
len = bio_add_zone_append_page(bio, page, PAGE_SIZE, 0);
else
len = bio_add_page(bio, page, PAGE_SIZE, 0);
page->mapping = NULL;
if (submit || len < PAGE_SIZE) {
[FIX]
It's no longer possible to revert to the original code style as we have
two different bio_add_*_page() calls now.
The new fix is to skip the bio_add_*_page() call if @submit is true.
Also to avoid @len to be uninitialized, always initialize it to zero.
If @submit is true, @len will not be checked.
If @submit is not true, @len will be the return value of
bio_add_*_page() call.
Either way, the behavior is still the same as the old code.
Reported-by: Josef Bacik <josef@xxxxxxxxxxxxxx>
Fixes: 764c7c9a464b ("btrfs: zoned: fix parallel compressed writes")
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@xxxxxxx>
Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
Signed-off-by: David Sterba <dsterba@xxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
diff --git a/fs/btrfs/compression.c b/fs/btrfs/compression.c
index fe0ec3d321b8..752b3cffe226 100644
--- a/fs/btrfs/compression.c
+++ b/fs/btrfs/compression.c
@@ -457,7 +457,7 @@ blk_status_t btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start,
bytes_left = compressed_len;
for (pg_index = 0; pg_index < cb->nr_pages; pg_index++) {
int submit = 0;
- int len;
+ int len = 0;
page = compressed_pages[pg_index];
page->mapping = inode->vfs_inode.i_mapping;
@@ -465,10 +465,17 @@ blk_status_t btrfs_submit_compressed_write(struct btrfs_inode *inode, u64 start,
submit = btrfs_bio_fits_in_stripe(page, PAGE_SIZE, bio,
0);
- if (pg_index == 0 && use_append)
- len = bio_add_zone_append_page(bio, page, PAGE_SIZE, 0);
- else
- len = bio_add_page(bio, page, PAGE_SIZE, 0);
+ /*
+ * Page can only be added to bio if the current bio fits in
+ * stripe.
+ */
+ if (!submit) {
+ if (pg_index == 0 && use_append)
+ len = bio_add_zone_append_page(bio, page,
+ PAGE_SIZE, 0);
+ else
+ len = bio_add_page(bio, page, PAGE_SIZE, 0);
+ }
page->mapping = NULL;
if (submit || len < PAGE_SIZE) {
