kernel.git/drivers/md/dm-thin-metadata.c, branch linux-4.9.y

dm thin: Use last transaction's pmd->root when commit failed

2023-01-07T11:07:36Z

commit 7991dbff6849f67e823b7cc0c15e5a90b0549b9f upstream. Recently we found a softlock up problem in dm thin pool btree lookup code due to corrupted metadata: Kernel panic - not syncing: softlockup: hung tasks CPU: 7 PID: 2669225 Comm: kworker/u16:3 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996) Workqueue: dm-thin do_worker [dm_thin_pool] Call Trace: dump_stack+0x9c/0xd3 panic+0x35d/0x6b9 watchdog_timer_fn.cold+0x16/0x25 __run_hrtimer+0xa2/0x2d0 RIP: 0010:__relink_lru+0x102/0x220 [dm_bufio] __bufio_new+0x11f/0x4f0 [dm_bufio] new_read+0xa3/0x1e0 [dm_bufio] dm_bm_read_lock+0x33/0xd0 [dm_persistent_data] ro_step+0x63/0x100 [dm_persistent_data] btree_lookup_raw.constprop.0+0x44/0x220 [dm_persistent_data] dm_btree_lookup+0x16f/0x210 [dm_persistent_data] dm_thin_find_block+0x12c/0x210 [dm_thin_pool] __process_bio_read_only+0xc5/0x400 [dm_thin_pool] process_thin_deferred_bios+0x1a4/0x4a0 [dm_thin_pool] process_one_work+0x3c5/0x730 Following process may generate a broken btree mixed with fresh and stale btree nodes, which could get dm thin trapped in an infinite loop while looking up data block: Transaction 1: pmd->root = A, A->B->C // One path in btree pmd->root = X, X->Y->Z // Copy-up Transaction 2: X,Z is updated on disk, Y write failed. // Commit failed, dm thin becomes read-only. process_bio_read_only dm_thin_find_block __find_block dm_btree_lookup(pmd->root) The pmd->root points to a broken btree, Y may contain stale node pointing to any block, for example X, which gets dm thin trapped into a dead loop while looking up Z. Fix this by setting pmd->root in __open_metadata(), so that dm thin will use the last transaction's pmd->root if commit failed. Fetch a reproducer in [Link]. Linke: https://bugzilla.kernel.org/show_bug.cgi?id=216790 Cc: stable@vger.kernel.org Fixes: 991d9fa02da0 ("dm: add thin provisioning target") Signed-off-by: Zhihao Cheng Acked-by: Joe Thornber Signed-off-by: Mike Snitzer Signed-off-by: Greg Kroah-Hartman

dm thin metadata: Avoid returning cmd->bm wild pointer on error

2020-09-12T09:47:37Z

commit 219403d7e56f9b716ad80ab87db85d29547ee73e upstream. Maybe __create_persistent_data_objects() caller will use PTR_ERR as a pointer, it will lead to some strange things. Signed-off-by: Ye Bin Cc: stable@vger.kernel.org Signed-off-by: Mike Snitzer Signed-off-by: Greg Kroah-Hartman

dm thin: fix passdown_double_checking_shared_status()

2019-01-31T07:12:36Z

commit d445bd9cec1a850c2100fcf53684c13b3fd934f2 upstream. Commit 00a0ea33b495 ("dm thin: do not queue freed thin mapping for next stage processing") changed process_prepared_discard_passdown_pt1() to increment all the blocks being discarded until after the passdown had completed to avoid them being prematurely reused. IO issued to a thin device that breaks sharing with a snapshot, followed by a discard issued to snapshot(s) that previously shared the block(s), results in passdown_double_checking_shared_status() being called to iterate through the blocks double checking their reference count is zero and issuing the passdown if so. So a side effect of commit 00a0ea33b495 is passdown_double_checking_shared_status() was broken. Fix this by checking if the block reference count is greater than 1. Also, rename dm_pool_block_is_used() to dm_pool_block_is_shared(). Fixes: 00a0ea33b495 ("dm thin: do not queue freed thin mapping for next stage processing") Cc: stable@vger.kernel.org # 4.9+ Reported-by: ryan.p.norwood@gmail.com Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer Signed-off-by: Greg Kroah-Hartman

dm thin metadata: fix __udivdi3 undefined on 32-bit

2018-10-10T06:53:23Z

commit 013ad043906b2befd4a9bfb06219ed9fedd92716 upstream. sector_div() is only viable for use with sector_t. dm_block_t is typedef'd to uint64_t -- so use div_u64() instead. Fixes: 3ab918281 ("dm thin metadata: try to avoid ever aborting transactions") Signed-off-by: Mike Snitzer Cc: Sudip Mukherjee Signed-off-by: Greg Kroah-Hartman

dm thin metadata: try to avoid ever aborting transactions

2018-10-10T06:53:21Z

[ Upstream commit 3ab91828166895600efd9cdc3a0eb32001f7204a ] Committing a transaction can consume some metadata of it's own, we now reserve a small amount of metadata to cover this. Free metadata reported by the kernel will not include this reserve. If any of the reserve has been used after a commit we enter a new internal state PM_OUT_OF_METADATA_SPACE. This is reported as PM_READ_ONLY, so no userland changes are needed. If the metadata device is resized the pool will move back to PM_WRITE. These changes mean we never need to abort and rollback a transaction due to running out of metadata space. This is particularly important because there have been a handful of reports of data corruption against DM thin-provisioning that can all be attributed to the thin-pool having ran out of metadata space. Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman

dm thin metadata: THIN_MAX_CONCURRENT_LOCKS should be 6

2018-01-23T18:57:09Z

commit 490ae017f54e55bde382d45ea24bddfb6d1a0aaf upstream. For btree removal, there is a corner case that a single thread could takes 6 locks which is more than THIN_MAX_CONCURRENT_LOCKS(5) and leads to deadlock. A btree removal might eventually call rebalance_children()->rebalance3() to rebalance entries of three neighbor child nodes when shadow_spine has already acquired two write locks. In rebalance3(), it tries to shadow and acquire the write locks of all three child nodes. However, shadowing a child node requires acquiring a read lock of the original child node and a write lock of the new block. Although the read lock will be released after block shadowing, shadowing the third child node in rebalance3() could still take the sixth lock. (2 write locks for shadow_spine + 2 write locks for the first two child nodes's shadow + 1 write lock for the last child node's shadow + 1 read lock for the last child node) Signed-off-by: Dennis Yang Acked-by: Joe Thornber Signed-off-by: Mike Snitzer Signed-off-by: Greg Kroah-Hartman

dm thin metadata: call precommit before saving the roots

2017-05-25T13:44:33Z

commit 91bcdb92d39711d1adb40c26b653b7978d93eb98 upstream. These calls were the wrong way round in __write_initial_superblock. Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer Signed-off-by: Greg Kroah-Hartman

dm thin: fix a race condition between discarding and provisioning a block

2016-07-20T16:43:35Z

The discard passdown was being issued after the block was unmapped, which meant the block could be reprovisioned whilst the passdown discard was still in flight. We can only identify unshared blocks (safe to do a passdown a discard to) once they're unmapped and their ref count hits zero. Block ref counts are now used to guard against concurrent allocation of these blocks that are being discarded. So now we unmap the block, issue passdown discards, and the immediately increment ref counts for regions that have been discarded via passed down (this is safe because allocation occurs within the same thread). We then decrement ref counts once the passdown discard IO is complete -- signaling these blocks may now be allocated. This fixes the potential for corruption that was reported here: https://www.redhat.com/archives/dm-devel/2016-June/msg00311.html Reported-by: Dennis Yang Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer

dm thin metadata: don't issue prefetches if a transaction abort has failed

2016-03-10T22:12:09Z

If a transaction abort has failed then we can no longer use the metadata device. Typically this happens if the superblock is unreadable. This fix addresses a crash seen during metadata device failure testing. Fixes: 8a01a6af75 ("dm thin: prefetch missing metadata pages") Cc: stable@vger.kernel.org # 3.19+ Signed-off-by: Joe Thornber Signed-off-by: Mike Snitzer

dm thin metadata: remove needless newline from subtree_dec() DMERR message

2016-03-10T22:12:05Z

Signed-off-by: Mike Snitzer