From f4a01017d678fe4baecf480e79d7c4f4b7ebc772 Mon Sep 17 00:00:00 2001 From: Theodore Ts'o Date: Sun, 5 Jul 2009 22:08:16 -0400 Subject: [PATCH] ext4: Fix potential reclaim deadlock when truncating partial block The ext4_block_truncate_page() function previously called grab_cache_page(), which called find_or_create_page() with the __GFP_FS flag potentially set. This could cause a deadlock if the system is low on memory and it attempts a memory reclaim, which could potentially call back into ext4. So we need to call find_or_create_page() directly, and remove the __GFP_FP flag to avoid this potential deadlock. Thanks to Roland Dreier for reporting a lockdep warning which showed this problem. [20786.363249] ================================= [20786.363257] [ INFO: inconsistent lock state ] [20786.363265] 2.6.31-2-generic #14~rbd4gitd960eea9 [20786.363270] --------------------------------- [20786.363276] inconsistent {IN-RECLAIM_FS-W} -> {RECLAIM_FS-ON-W} usage. [20786.363285] http/8397 [HC0[0]:SC0[0]:HE1:SE1] takes: [20786.363291] (jbd2_handle){+.+.?.}, at: [] jbd2_journal_start+0xdb/0x150 [20786.363314] {IN-RECLAIM_FS-W} state was registered at: [20786.363320] [] mark_irqflags+0xc6/0x1a0 [20786.363334] [] __lock_acquire+0x287/0x430 [20786.363345] [] lock_acquire+0xa5/0x150 [20786.363355] [] jbd2_journal_start+0xfa/0x150 [20786.363365] [] ext4_journal_start_sb+0x58/0x90 [20786.363377] [] ext4_delete_inode+0xc5/0x2c0 [20786.363389] [] generic_delete_inode+0xd3/0x1a0 [20786.363401] [] generic_drop_inode+0x25/0x30 [20786.363411] [] iput+0x62/0x70 [20786.363420] [] dentry_iput+0x98/0x110 [20786.363429] [] d_kill+0x50/0x80 [20786.363438] [] dput+0x95/0x180 [20786.363447] [] ecryptfs_d_release+0x2b/0x70 [20786.363459] [] d_free+0x28/0x60 [20786.363468] [] d_kill+0x68/0x80 [20786.363477] [] prune_one_dentry+0xa3/0xc0 [20786.363487] [] __shrink_dcache_sb+0x271/0x290 [20786.363497] [] prune_dcache+0x109/0x1b0 [20786.363506] [] shrink_dcache_memory+0x3f/0x50 [20786.363516] [] shrink_slab+0x12d/0x190 [20786.363527] [] balance_pgdat+0x4d7/0x640 [20786.363537] [] kswapd+0x117/0x170 [20786.363546] [] kthread+0x9e/0xb0 [20786.363558] [] child_rip+0xa/0x20 [20786.363569] [] 0xffffffffffffffff [20786.363598] irq event stamp: 15997 [20786.363603] hardirqs last enabled at (15997): [] kmem_cache_alloc+0xfd/0x1a0 [20786.363617] hardirqs last disabled at (15996): [] kmem_cache_alloc+0x61/0x1a0 [20786.363628] softirqs last enabled at (15966): [] __do_softirq+0x14a/0x220 [20786.363641] softirqs last disabled at (15861): [] call_softirq+0x1c/0x30 [20786.363651] [20786.363653] other info that might help us debug this: [20786.363660] 3 locks held by http/8397: [20786.363665] #0: (&sb->s_type->i_mutex_key#8){+.+.+.}, at: [] do_truncate+0x64/0x90 [20786.363685] #1: (&sb->s_type->i_alloc_sem_key#5){+++++.}, at: [] notify_change+0x250/0x350 [20786.363707] #2: (jbd2_handle){+.+.?.}, at: [] jbd2_journal_start+0xdb/0x150 [20786.363724] [20786.363726] stack backtrace: [20786.363734] Pid: 8397, comm: http Tainted: G C 2.6.31-2-generic #14~rbd4gitd960eea9 [20786.363741] Call Trace: [20786.363752] [] print_usage_bug+0x18c/0x1a0 [20786.363763] [] ? check_usage_backwards+0x0/0xb0 [20786.363773] [] mark_lock_irq+0xf2/0x280 [20786.363783] [] mark_lock+0x137/0x1d0 [20786.363793] [] mark_held_locks+0x6c/0xa0 [20786.363803] [] lockdep_trace_alloc+0xaf/0xe0 [20786.363813] [] __alloc_pages_nodemask+0x7c/0x180 [20786.363824] [] ? find_get_page+0x91/0xf0 [20786.363835] [] alloc_pages_current+0x87/0xd0 [20786.363845] [] __page_cache_alloc+0x67/0x70 [20786.363856] [] find_or_create_page+0x4f/0xb0 [20786.363867] [] ext4_block_truncate_page+0x3e/0x460 [20786.363876] [] ? jbd2_journal_start+0xfa/0x150 [20786.363885] [] ? jbd2_journal_start+0xdb/0x150 [20786.363895] [] ? ext4_meta_trans_blocks+0x75/0xf0 [20786.363905] [] ext4_ext_truncate+0x1bb/0x1e0 [20786.363916] [] ? unmap_mapping_range+0x75/0x290 [20786.363926] [] ext4_truncate+0x498/0x630 [20786.363938] [] ? _raw_spin_unlock+0x5e/0xb0 [20786.363947] [] ? unmap_mapping_range+0xb6/0x290 [20786.363957] [] ? trace_hardirqs_on+0xd/0x10 [20786.363966] [] ? jbd2_journal_stop+0x1f8/0x2e0 [20786.363976] [] vmtruncate+0xb0/0x110 [20786.363986] [] inode_setattr+0x35/0x170 [20786.363995] [] ext4_setattr+0x186/0x370 [20786.364005] [] notify_change+0x16b/0x350 [20786.364014] [] do_truncate+0x70/0x90 [20786.364021] [] T.657+0xeb/0x110 [20786.364021] [] sys_ftruncate+0xe/0x10 [20786.364021] [] system_call_fastpath+0x16/0x1b Reported-by: Roland Dreier Signed-off-by: "Theodore Ts'o" --- fs/ext4/inode.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 60a26f3a6f8..9760ba09275 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -3583,7 +3583,8 @@ int ext4_block_truncate_page(handle_t *handle, struct page *page; int err = 0; - page = grab_cache_page(mapping, from >> PAGE_CACHE_SHIFT); + page = find_or_create_page(mapping, from >> PAGE_CACHE_SHIFT, + mapping_gfp_mask(mapping) & ~__GFP_FS); if (!page) return -EINVAL; -- 2.11.4.GIT