@@ -7027,6 +7027,7 @@ static noinline int find_free_extent(struct btrfs_root *orig_root,
bool failed_alloc = false;
bool use_cluster = true;
bool have_caching_bg = false;
+ bool orig_have_caching_bg = false;
bool full_search = false;
WARN_ON(num_bytes < root->sectorsize);
@@ -7376,6 +7377,9 @@ loop:
}
up_read(&space_info->groups_sem);
+ if ((loop == LOOP_CACHING_NOWAIT) && have_caching_bg && !orig_have_caching_bg)
+ orig_have_caching_bg = true;
+
if (!ins->objectid && loop >= LOOP_CACHING_WAIT && have_caching_bg)
goto search;
@@ -7398,7 +7402,7 @@ loop:
* don't have any unached bgs and we've alrelady done a
* full search through.
*/
- if (have_caching_bg || !full_search)
+ if (orig_have_caching_bg || !full_search)
loop = LOOP_CACHING_WAIT;
else
loop = LOOP_ALLOC_CHUNK;
When executing generic/001 in a loop on a ppc64 machine (with both sectorsize and nodesize set to 64k), the following call trace is observed, WARNING: at /root/repos/linux/fs/btrfs/locking.c:253 Modules linked in: CPU: 2 PID: 8353 Comm: umount Not tainted 4.3.0-rc5-13676-ga5e681d #54 task: c0000000f2b1f560 ti: c0000000f6008000 task.ti: c0000000f6008000 NIP: c000000000520c88 LR: c0000000004a3b34 CTR: 0000000000000000 REGS: c0000000f600a820 TRAP: 0700 Not tainted (4.3.0-rc5-13676-ga5e681d) MSR: 8000000102029032 <SF,VEC,EE,ME,IR,DR,RI> CR: 24444884 XER: 00000000 CFAR: c0000000004a3b30 SOFTE: 1 GPR00: c0000000004a3b34 c0000000f600aaa0 c00000000108ac00 c0000000f5a808c0 GPR04: 0000000000000000 c0000000f600ae60 0000000000000000 0000000000000005 GPR08: 00000000000020a1 0000000000000001 c0000000f2b1f560 0000000000000030 GPR12: 0000000084842882 c00000000fdc0900 c0000000f600ae60 c0000000f070b800 GPR16: 0000000000000000 c0000000f3c8a000 0000000000000000 0000000000000049 GPR20: 0000000000000001 0000000000000001 c0000000f5aa01f8 0000000000000000 GPR24: 0f83e0f83e0f83e1 c0000000f5a808c0 c0000000f3c8d000 c000000000000000 GPR28: c0000000f600ae74 0000000000000001 c0000000f3c8d000 c0000000f5a808c0 NIP [c000000000520c88] .btrfs_tree_lock+0x48/0x2a0 LR [c0000000004a3b34] .btrfs_lock_root_node+0x44/0x80 Call Trace: [c0000000f600aaa0] [c0000000f600ab80] 0xc0000000f600ab80 (unreliable) [c0000000f600ab80] [c0000000004a3b34] .btrfs_lock_root_node+0x44/0x80 [c0000000f600ac00] [c0000000004a99dc] .btrfs_search_slot+0xa8c/0xc00 [c0000000f600ad40] [c0000000004ab878] .btrfs_insert_empty_items+0x98/0x120 [c0000000f600adf0] [c00000000050da44] .btrfs_finish_chunk_alloc+0x1d4/0x620 [c0000000f600af20] [c0000000004be854] .btrfs_create_pending_block_groups+0x1d4/0x2c0 [c0000000f600b020] [c0000000004bf188] .do_chunk_alloc+0x3c8/0x420 [c0000000f600b100] [c0000000004c27cc] .find_free_extent+0xbfc/0x1030 [c0000000f600b260] [c0000000004c2ce8] .btrfs_reserve_extent+0xe8/0x250 [c0000000f600b330] [c0000000004c2f90] .btrfs_alloc_tree_block+0x140/0x590 [c0000000f600b440] [c0000000004a47b4] .__btrfs_cow_block+0x124/0x780 [c0000000f600b530] [c0000000004a4fc0] .btrfs_cow_block+0xf0/0x250 [c0000000f600b5e0] [c0000000004a917c] .btrfs_search_slot+0x22c/0xc00 [c0000000f600b720] [c00000000050aa40] .btrfs_remove_chunk+0x1b0/0x9f0 [c0000000f600b850] [c0000000004c4e04] .btrfs_delete_unused_bgs+0x434/0x570 [c0000000f600b950] [c0000000004d3cb8] .close_ctree+0x2e8/0x3b0 [c0000000f600ba20] [c00000000049d178] .btrfs_put_super+0x18/0x30 [c0000000f600ba90] [c000000000243cd4] .generic_shutdown_super+0xa4/0x1a0 [c0000000f600bb10] [c0000000002441d8] .kill_anon_super+0x18/0x30 [c0000000f600bb90] [c00000000049c898] .btrfs_kill_super+0x18/0xc0 [c0000000f600bc10] [c0000000002444f8] .deactivate_locked_super+0x98/0xe0 [c0000000f600bc90] [c000000000269f94] .cleanup_mnt+0x54/0xa0 [c0000000f600bd10] [c0000000000bd744] .task_work_run+0xc4/0x100 [c0000000f600bdb0] [c000000000016334] .do_notify_resume+0x74/0x80 [c0000000f600be30] [c0000000000098b8] .ret_from_except_lite+0x64/0x68 Instruction dump: fba1ffe8 fbc1fff0 fbe1fff8 7c791b78 f8010010 f821ff21 e94d0290 81030040 812a04e8 7d094a78 7d290034 5529d97e <0b090000> 3b400000 3be30050 3bc3004c The above call trace is seen even on x86_64; albeit very rarely and that too with nodesize set to 64k and with nospace_cache mount option being used. The reason for the above call trace is, btrfs_remove_chunk check_system_chunk Allocate chunk if required For each physical stripe on underlying device, btrfs_free_dev_extent ... Take lock on Device tree's root node btrfs_cow_block("dev tree's root node"); btrfs_reserve_extent find_free_extent index = BTRFS_RAID_DUP; have_caching_bg = false; When in LOOP_CACHING_NOWAIT state, Assume we find a block group which is being cached; Hence have_caching_bg is set to true When repeating the search for the next RAID index, we set have_caching_bg to false. Hence right after completing the LOOP_CACHING_NOWAIT state, we incorrectly skip LOOP_CACHING_WAIT state and move to LOOP_ALLOC_CHUNK state where we allocate a chunk and try to add entries corresponding to the chunk's physical stripe into the device tree. When doing so the task deadlocks itself waiting for the blocking lock on the root node of the device tree. This commit fixes the issue by introducing a new local variable to help indicate as to whether a block group of any RAID type is being cached. Signed-off-by: Chandan Rajendra <chandan@linux.vnet.ibm.com> --- fs/btrfs/extent-tree.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)