kernel.git/fs/btrfs/raid56.c, branch linux-4.16.y

btrfs: Fix NULL pointer exception in find_bio_stripe

2018-03-14T21:26:35Z

On detaching of a disk which is a part of a RAID6 filesystem, the following kernel OOPS may happen: [63122.680461] BTRFS error (device sdo): bdev /dev/sdo errs: wr 0, rd 0, flush 1, corrupt 0, gen 0 [63122.719584] BTRFS warning (device sdo): lost page write due to IO error on /dev/sdo [63122.719587] BTRFS error (device sdo): bdev /dev/sdo errs: wr 1, rd 0, flush 1, corrupt 0, gen 0 [63122.803516] BTRFS warning (device sdo): lost page write due to IO error on /dev/sdo [63122.803519] BTRFS error (device sdo): bdev /dev/sdo errs: wr 2, rd 0, flush 1, corrupt 0, gen 0 [63122.863902] BTRFS critical (device sdo): fatal error on device /dev/sdo [63122.935338] BUG: unable to handle kernel NULL pointer dereference at 0000000000000080 [63122.946554] IP: fail_bio_stripe+0x58/0xa0 [btrfs] [63122.958185] PGD 9ecda067 P4D 9ecda067 PUD b2b37067 PMD 0 [63122.971202] Oops: 0000 [#1] SMP [63123.006760] CPU: 0 PID: 3979 Comm: kworker/u8:9 Tainted: G W 4.14.2-16-scst34x+ #8 [63123.007091] Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006 [63123.007402] Workqueue: btrfs-worker btrfs_worker_helper [btrfs] [63123.007595] task: ffff880036ea4040 task.stack: ffffc90006384000 [63123.007796] RIP: 0010:fail_bio_stripe+0x58/0xa0 [btrfs] [63123.007968] RSP: 0018:ffffc90006387ad8 EFLAGS: 00010287 [63123.008140] RAX: 0000000000000002 RBX: ffff88004beaa0b8 RCX: ffff8800b2bd5690 [63123.008359] RDX: 0000000000000000 RSI: ffff88007bb43500 RDI: ffff88004beaa000 [63123.008621] RBP: ffffc90006387ae8 R08: 0000000099100000 R09: ffff8800b2bd5600 [63123.008840] R10: 0000000000000004 R11: 0000000000010000 R12: ffff88007bb43500 [63123.009059] R13: 00000000fffffffb R14: ffff880036fc5180 R15: 0000000000000004 [63123.009278] FS: 0000000000000000(0000) GS:ffff8800b7000000(0000) knlGS:0000000000000000 [63123.009564] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [63123.009748] CR2: 0000000000000080 CR3: 00000000b0866000 CR4: 00000000000406f0 [63123.009969] Call Trace: [63123.010085] raid_write_end_io+0x7e/0x80 [btrfs] [63123.010251] bio_endio+0xa1/0x120 [63123.010378] generic_make_request+0x218/0x270 [63123.010921] submit_bio+0x66/0x130 [63123.011073] finish_rmw+0x3fc/0x5b0 [btrfs] [63123.011245] full_stripe_write+0x96/0xc0 [btrfs] [63123.011428] raid56_parity_write+0x117/0x170 [btrfs] [63123.011604] btrfs_map_bio+0x2ec/0x320 [btrfs] [63123.011759] ? ___cache_free+0x1c5/0x300 [63123.011909] __btrfs_submit_bio_done+0x26/0x50 [btrfs] [63123.012087] run_one_async_done+0x9c/0xc0 [btrfs] [63123.012257] normal_work_helper+0x19e/0x300 [btrfs] [63123.012429] btrfs_worker_helper+0x12/0x20 [btrfs] [63123.012656] process_one_work+0x14d/0x350 [63123.012888] worker_thread+0x4d/0x3a0 [63123.013026] ? _raw_spin_unlock_irqrestore+0x15/0x20 [63123.013192] kthread+0x109/0x140 [63123.013315] ? process_scheduled_works+0x40/0x40 [63123.013472] ? kthread_stop+0x110/0x110 [63123.013610] ret_from_fork+0x25/0x30 [63123.014469] RIP: fail_bio_stripe+0x58/0xa0 [btrfs] RSP: ffffc90006387ad8 [63123.014678] CR2: 0000000000000080 [63123.016590] ---[ end trace a295ea7259c17880 ]— This is reproducible in a cycle, where a series of writes is followed by SCSI device delete command. The test may take up to few minutes. Fixes: 74d46992e0d9 ("block: replace bi_bdev with a gendisk pointer and partitions index") [ no signed-off-by provided ] Author: Dmitriy Gorokh Reviewed-by: Liu Bo Reviewed-by: David Sterba Signed-off-by: David Sterba

Btrfs: raid56: fix race between merge_bio and rbio_orig_end_io

2018-01-22T15:08:21Z

Before rbio_orig_end_io() goes to free rbio, rbio may get merged with more bios from other rbios and rbio->bio_list becomes non-empty, in that case, these newly merged bios don't end properly. Once unlock_stripe() is done, rbio->bio_list will not be updated any more and we can call bio_endio() on all queued bios. It should only happen in error-out cases, the normal path of recover and full stripe write have already set RBIO_RMW_LOCKED_BIT to disable merge before doing IO, so rbio_orig_end_io() called by them doesn't have the above issue. Reported-by: Jérôme Carretero Signed-off-by: Liu Bo Signed-off-by: David Sterba

Btrfs: do not cache rbio pages if using raid6 recover

2018-01-22T15:08:21Z

Since raid6 recover tries all possible combinations of failed stripes, - when raid6 rebuild algorithm is used, i.e. raid6_datap_recov() and raid6_2data_recov(), it may change the in-memory content of failed stripes, if such a raid bio is cached, a later raid write rmw or recover can steal @stripe_pages from it instead of reading from disks, such that it carries the wrong content to do write rmw or recovery and ends up with corruption or recovery failures. - when raid5 rebuild algorithm is used, i.e. xor, raid bio can be cached because the only failed stripe which contains @rbio->bio_pages gets modified, others remain the same so that their in-memory content is consistent with their on-disk content. This adds a check to skip caching rbio if using raid6 recover. Signed-off-by: Liu Bo Signed-off-by: David Sterba

Btrfs: raid56: iterate raid56 internal bio with bio_for_each_segment_all

2018-01-22T15:08:21Z

Bio iterated by set_bio_pages_uptodate() is raid56 internal one, so it will never be a BIO_CLONED bio, and since this is called by end_io functions, bio->bi_iter.bi_size is zero, we mustn't use bio_for_each_segment() as that is a no-op if bi_size is zero. Fixes: 6592e58c6b68e61f003a01ba29a3716e7e2e9484 ("Btrfs: fix write corruption due to bio cloning on raid5/6") Cc: # v4.12-rc6+ Signed-off-by: Liu Bo Signed-off-by: David Sterba

Btrfs: do not merge rbios if their fail stripe index are not identical

2018-01-22T15:08:20Z

Since fail stripe index in rbio would be used to decide which algorithm reconstruction would be run, we cannot merge rbios if their's fail striped indexes are different, otherwise, one of the two reconstructions would fail. Signed-off-by: Liu Bo Reviewed-by: David Sterba Signed-off-by: David Sterba

Btrfs: remove redundant check in rbio_can_merge

2018-01-22T15:08:20Z

Given the above ' if (last->operation != cur->operation) return 0; ', it's guaranteed that two operations are same. Signed-off-by: Liu Bo Reviewed-by: David Sterba Signed-off-by: David Sterba

Btrfs: make raid6 rebuild retry more

2018-01-22T15:08:20Z

There is a scenario that can end up with rebuild process failing to return good content, i.e. suppose that all disks can be read without problems and if the content that was read out doesn't match its checksum, currently for raid6 btrfs at most retries twice, - the 1st retry is to rebuild with all other stripes, it'll eventually be a raid5 xor rebuild, - if the 1st fails, the 2nd retry will deliberately fail parity p so that it will do raid6 style rebuild, however, the chances are that another non-parity stripe content also has something corrupted, so that the above retries are not able to return correct content, and users will think of this as data loss. More seriouly, if the loss happens on some important internal btree roots, it could refuse to mount. This extends btrfs to do more retries and each retry fails only one stripe. Since raid6 can tolerate 2 disk failures, if there is one more failure besides the failure on which we're recovering, this can always work. The worst case is to retry as many times as the number of raid6 disks, but given the fact that such a scenario is really rare in practice, it's still acceptable. Signed-off-by: Liu Bo Signed-off-by: David Sterba

Btrfs: remove unused wait in btrfs_stripe_hash

2018-01-22T15:08:19Z

In fact nobody is waiting on @wait's waitqueue, it can be safely removed. Signed-off-by: Liu Bo Reviewed-by: David Sterba Signed-off-by: David Sterba

Btrfs: remove unused variable wait in lock_stripe_add

2018-01-22T15:08:15Z

The defined wait is not used anywhere. Signed-off-by: Liu Bo Reviewed-by: David Sterba Signed-off-by: David Sterba

Btrfs: fix memory leak in raid56

2017-10-30T11:27:57Z

The local bio_list may have pending bios when doing cleanup, it can end up with memory leak if they don't get freed. Signed-off-by: Liu Bo Reviewed-by: David Sterba Signed-off-by: David Sterba