[PATCH 1/2] block: loop: set discard granularity and alignment for block device backed loop
From: Ming Lei ming.lei@redhat.com
mainline inclusion from mainline-v5.9-rc3 commit bcb21c8cc9947286211327d663ace69f07d37a76 category: bugfix bugzilla: NA CVE: NA
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In case of block device backend, if the backend supports write zeros, the loop device will set queue flag of QUEUE_FLAG_DISCARD. However, limits.discard_granularity isn't setup, and this way is wrong, see the following description in Documentation/ABI/testing/sysfs-block:
A discard_granularity of 0 means that the device does not support discard functionality.
Especially 9b15d109a6b2 ("block: improve discard bio alignment in __blkdev_issue_discard()") starts to take q->limits.discard_granularity for computing max discard sectors. And zero discard granularity may cause kernel oops, or fail discard request even though the loop queue claims discard support via QUEUE_FLAG_DISCARD.
Fix the issue by setup discard granularity and alignment.
Fixes: c52abf563049 ("loop: Better discard support for block devices") Signed-off-by: Ming Lei ming.lei@redhat.com Reviewed-by: Christoph Hellwig hch@lst.de Acked-by: Coly Li colyli@suse.de Cc: Hannes Reinecke hare@suse.com Cc: Xiao Ni xni@redhat.com Cc: Martin K. Petersen martin.petersen@oracle.com Cc: Evan Green evgreen@chromium.org Cc: Gwendal Grignou gwendal@chromium.org Cc: Chaitanya Kulkarni chaitanya.kulkarni@wdc.com Cc: Andrzej Pietrasiewicz andrzej.p@collabora.com Cc: Christoph Hellwig hch@lst.de Cc: stable@vger.kernel.org Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Yang Yingliang yangyingliang@huawei.com Reviewed-by: Yufen Yu yuyufen@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- drivers/block/loop.c | 33 ++++++++++++++++++--------------- 1 file changed, 18 insertions(+), 15 deletions(-)
diff --git a/drivers/block/loop.c b/drivers/block/loop.c index da68c42aed68..19042b42a8ba 100644 --- a/drivers/block/loop.c +++ b/drivers/block/loop.c @@ -864,6 +864,7 @@ static void loop_config_discard(struct loop_device *lo) struct file *file = lo->lo_backing_file; struct inode *inode = file->f_mapping->host; struct request_queue *q = lo->lo_queue; + u32 granularity, max_discard_sectors;
/* * If the backing device is a block device, mirror its zeroing @@ -876,11 +877,10 @@ static void loop_config_discard(struct loop_device *lo) struct request_queue *backingq;
backingq = bdev_get_queue(inode->i_bdev); - blk_queue_max_discard_sectors(q, - backingq->limits.max_write_zeroes_sectors);
- blk_queue_max_write_zeroes_sectors(q, - backingq->limits.max_write_zeroes_sectors); + max_discard_sectors = backingq->limits.max_write_zeroes_sectors; + granularity = backingq->limits.discard_granularity ?: + queue_physical_block_size(backingq);
/* * We use punch hole to reclaim the free space used by the @@ -889,23 +889,26 @@ static void loop_config_discard(struct loop_device *lo) * useful information. */ } else if (!file->f_op->fallocate || lo->lo_encrypt_key_size) { - q->limits.discard_granularity = 0; - q->limits.discard_alignment = 0; - blk_queue_max_discard_sectors(q, 0); - blk_queue_max_write_zeroes_sectors(q, 0); + max_discard_sectors = 0; + granularity = 0;
} else { - q->limits.discard_granularity = inode->i_sb->s_blocksize; - q->limits.discard_alignment = 0; - - blk_queue_max_discard_sectors(q, UINT_MAX >> 9); - blk_queue_max_write_zeroes_sectors(q, UINT_MAX >> 9); + max_discard_sectors = UINT_MAX >> 9; + granularity = inode->i_sb->s_blocksize; }
- if (q->limits.max_write_zeroes_sectors) + if (max_discard_sectors) { + q->limits.discard_granularity = granularity; + blk_queue_max_discard_sectors(q, max_discard_sectors); + blk_queue_max_write_zeroes_sectors(q, max_discard_sectors); blk_queue_flag_set(QUEUE_FLAG_DISCARD, q); - else + } else { + q->limits.discard_granularity = 0; + blk_queue_max_discard_sectors(q, 0); + blk_queue_max_write_zeroes_sectors(q, 0); blk_queue_flag_clear(QUEUE_FLAG_DISCARD, q); + } + q->limits.discard_alignment = 0; }
static void loop_unprepare_queue(struct loop_device *lo)
From: Coly Li colyli@suse.de
mainline inclusion from mainline-v5.9-rc1 commit b35fd7422c2f8e04496f5a770bd4e1a205414b3f category: bugfix bugzilla: NA CVE: NA
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If create a loop device with a backing NVMe SSD, current loop device driver doesn't correctly set its queue's limits.discard_granularity and leaves it as 0. If a discard request at LBA 0 on this loop device, in __blkdev_issue_discard() the calculated req_sects will be 0, and a zero length discard request will trigger a BUG() panic in generic block layer code at block/blk-mq.c:563.
[ 955.565006][ C39] ------------[ cut here ]------------ [ 955.559660][ C39] invalid opcode: 0000 [#1] SMP NOPTI [ 955.622171][ C39] CPU: 39 PID: 248 Comm: ksoftirqd/39 Tainted: G E 5.8.0-default+ #40 [ 955.622171][ C39] Hardware name: Lenovo ThinkSystem SR650 -[7X05CTO1WW]-/-[7X05CTO1WW]-, BIOS -[IVE160M-2.70]- 07/17/2020 [ 955.622175][ C39] RIP: 0010:blk_mq_end_request+0x107/0x110 [ 955.622177][ C39] Code: 48 8b 03 e9 59 ff ff ff 48 89 df 5b 5d 41 5c e9 9f ed ff ff 48 8b 35 98 3c f4 00 48 83 c7 10 48 83 c6 19 e8 cb 56 c9 ff eb cb <0f> 0b 0f 1f 80 00 00 00 00 0f 1f 44 00 00 55 48 89 e5 41 56 41 54 [ 955.622179][ C39] RSP: 0018:ffffb1288701fe28 EFLAGS: 00010202 [ 955.749277][ C39] RAX: 0000000000000001 RBX: ffff956fffba5080 RCX: 0000000000004003 [ 955.749278][ C39] RDX: 0000000000000003 RSI: 0000000000000000 RDI: 0000000000000000 [ 955.749279][ C39] RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000 [ 955.749279][ C39] R10: ffffb1288701fd28 R11: 0000000000000001 R12: ffffffffa8e05160 [ 955.749280][ C39] R13: 0000000000000004 R14: 0000000000000004 R15: ffffffffa7ad3a1e [ 955.749281][ C39] FS: 0000000000000000(0000) GS:ffff95bfbda00000(0000) knlGS:0000000000000000 [ 955.749282][ C39] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 955.749282][ C39] CR2: 00007f6f0ef766a8 CR3: 0000005a37012002 CR4: 00000000007606e0 [ 955.749283][ C39] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000 [ 955.749284][ C39] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400 [ 955.749284][ C39] PKRU: 55555554 [ 955.749285][ C39] Call Trace: [ 955.749290][ C39] blk_done_softirq+0x99/0xc0 [ 957.550669][ C39] __do_softirq+0xd3/0x45f [ 957.550677][ C39] ? smpboot_thread_fn+0x2f/0x1e0 [ 957.550679][ C39] ? smpboot_thread_fn+0x74/0x1e0 [ 957.550680][ C39] ? smpboot_thread_fn+0x14e/0x1e0 [ 957.550684][ C39] run_ksoftirqd+0x30/0x60 [ 957.550687][ C39] smpboot_thread_fn+0x149/0x1e0 [ 957.886225][ C39] ? sort_range+0x20/0x20 [ 957.886226][ C39] kthread+0x137/0x160 [ 957.886228][ C39] ? kthread_park+0x90/0x90 [ 957.886231][ C39] ret_from_fork+0x22/0x30 [ 959.117120][ C39] ---[ end trace 3dacdac97e2ed164 ]---
This is the procedure to reproduce the panic, # modprobe scsi_debug delay=0 dev_size_mb=2048 max_queue=1 # losetup -f /dev/nvme0n1 --direct-io=on # blkdiscard /dev/loop0 -o 0 -l 0x200
This patch fixes the issue by checking q->limits.discard_granularity in __blkdev_issue_discard() before composing the discard bio. If the value is 0, then prints a warning oops information and returns -EOPNOTSUPP to the caller to indicate that this buggy device driver doesn't support discard request.
Fixes: 9b15d109a6b2 ("block: improve discard bio alignment in __blkdev_issue_discard()") Fixes: c52abf563049 ("loop: Better discard support for block devices") Reported-and-suggested-by: Ming Lei ming.lei@redhat.com Signed-off-by: Coly Li colyli@suse.de Reviewed-by: Ming Lei ming.lei@redhat.com Reviewed-by: Hannes Reinecke hare@suse.de Reviewed-by: Jack Wang jinpu.wang@cloud.ionos.com Cc: Bart Van Assche bvanassche@acm.org Cc: Christoph Hellwig hch@lst.de Cc: Darrick J. Wong darrick.wong@oracle.com Cc: Enzo Matsumiya ematsumiya@suse.com Cc: Evan Green evgreen@chromium.org Cc: Jens Axboe axboe@kernel.dk Cc: Martin K. Petersen martin.petersen@oracle.com Cc: Xiao Ni xni@redhat.com Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Yang Yingliang yangyingliang@huawei.com Reviewed-by: Yufen Yu yuyufen@huawei.com Signed-off-by: Yang Yingliang yangyingliang@huawei.com --- block/blk-lib.c | 9 +++++++++ 1 file changed, 9 insertions(+)
diff --git a/block/blk-lib.c b/block/blk-lib.c index 0dbc9e2ab9a3..71a551a497ea 100644 --- a/block/blk-lib.c +++ b/block/blk-lib.c @@ -48,6 +48,15 @@ int __blkdev_issue_discard(struct block_device *bdev, sector_t sector, op = REQ_OP_DISCARD; }
+ /* In case the discard granularity isn't set by buggy device driver */ + if (WARN_ON_ONCE(!q->limits.discard_granularity)) { + char dev_name[BDEVNAME_SIZE]; + + bdevname(bdev, dev_name); + pr_err_ratelimited("%s: Error: discard_granularity is 0.\n", dev_name); + return -EOPNOTSUPP; + } + bs_mask = (bdev_logical_block_size(bdev) >> 9) - 1; if ((sector | nr_sects) & bs_mask) return -EINVAL;
-
Yang Yingliang