From 795e633a2dc6cbbeac68bc7f6006082150d38bb7 Mon Sep 17 00:00:00 2001 From: Mike Snitzer Date: Wed, 29 Jul 2015 13:48:23 -0400 Subject: [PATCH] dm cache: fix device destroy hang due to improper prealloc_used accounting Commit 665022d72f9 ("dm cache: avoid calls to prealloc_free_structs() if possible") introduced a regression that caused the removal of a DM cache device to hang in cache_postsuspend()'s call to wait_for_migrations() with the following stack trace: [] schedule+0x37/0x80 [] cache_postsuspend+0xbb/0x470 [dm_cache] [] ? prepare_to_wait_event+0xf0/0xf0 [] dm_table_postsuspend_targets+0x47/0x60 [dm_mod] [] __dm_destroy+0x215/0x250 [dm_mod] [] dm_destroy+0x13/0x20 [dm_mod] [] dev_remove+0x10d/0x170 [dm_mod] [] ? dev_suspend+0x240/0x240 [dm_mod] [] ctl_ioctl+0x255/0x4d0 [dm_mod] [] ? SYSC_semtimedop+0x280/0xe10 [] dm_ctl_ioctl+0x13/0x20 [dm_mod] [] do_vfs_ioctl+0x2d2/0x4b0 [] ? __audit_syscall_entry+0xaf/0x100 [] ? do_audit_syscall_entry+0x66/0x70 [] SyS_ioctl+0x79/0x90 [] ? syscall_trace_leave+0xb8/0x110 [] entry_SYSCALL_64_fastpath+0x12/0x71 Fix this by accounting for the call to prealloc_data_structs() immediately _before_ the call as opposed to after. This is needed because it is possible to break out of the control loop after the call to prealloc_data_structs() but before prealloc_used was set to true. Signed-off-by: Mike Snitzer --- drivers/md/dm-cache-target.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/drivers/md/dm-cache-target.c b/drivers/md/dm-cache-target.c index 64e96a2bed58..1fe93cfea7d3 100644 --- a/drivers/md/dm-cache-target.c +++ b/drivers/md/dm-cache-target.c @@ -1967,6 +1967,7 @@ static void process_deferred_bios(struct cache *cache) * this bio might require one, we pause until there are some * prepared mappings to process. */ + prealloc_used = true; if (prealloc_data_structs(cache, &structs)) { spin_lock_irqsave(&cache->lock, flags); bio_list_merge(&cache->deferred_bios, &bios); @@ -1982,7 +1983,6 @@ static void process_deferred_bios(struct cache *cache) process_discard_bio(cache, &structs, bio); else process_bio(cache, &structs, bio); - prealloc_used = true; } if (prealloc_used) @@ -2011,6 +2011,7 @@ static void process_deferred_cells(struct cache *cache) * this bio might require one, we pause until there are some * prepared mappings to process. */ + prealloc_used = true; if (prealloc_data_structs(cache, &structs)) { spin_lock_irqsave(&cache->lock, flags); list_splice(&cells, &cache->deferred_cells); @@ -2019,7 +2020,6 @@ static void process_deferred_cells(struct cache *cache) } process_cell(cache, &structs, cell); - prealloc_used = true; } if (prealloc_used) @@ -2081,6 +2081,7 @@ static void writeback_some_dirty_blocks(struct cache *cache) if (policy_writeback_work(cache->policy, &oblock, &cblock, busy)) break; /* no work to do */ + prealloc_used = true; if (prealloc_data_structs(cache, &structs) || get_cell(cache, oblock, &structs, &old_ocell)) { policy_set_dirty(cache->policy, oblock); @@ -2088,7 +2089,6 @@ static void writeback_some_dirty_blocks(struct cache *cache) } writeback(cache, &structs, oblock, cblock, old_ocell); - prealloc_used = true; } if (prealloc_used) -- 2.20.1