From 500f5a0bf5f0624dae34307010e240ec090e4cde Mon Sep 17 00:00:00 2001 From: Frederic Weisbecker Date: Sun, 13 Dec 2009 22:48:54 +0100 Subject: [PATCH] reiserfs: Fix possible recursive lock While allocating the bitmap using vmalloc, we hold the reiserfs lock, which makes lockdep later reporting a possible deadlock as we may swap out pages to allocate memory and then take the reiserfs lock recursively: inconsistent {RECLAIM_FS-ON-W} -> {IN-RECLAIM_FS-W} usage. kswapd0/312 [HC0[0]:SC0[0]:HE1:SE1] takes: (&REISERFS_SB(s)->lock){+.+.?.}, at: [] reiserfs_write_lock+0x28/0x40 {RECLAIM_FS-ON-W} state was registered at: [] mark_held_locks+0x62/0x90 [] lockdep_trace_alloc+0x9a/0xc0 [] kmem_cache_alloc+0x26/0xf0 [] __get_vm_area_node+0x6c/0xf0 [] __vmalloc_node+0x7e/0xa0 [] vmalloc+0x2b/0x30 [] reiserfs_init_bitmap_cache+0x39/0x70 [] reiserfs_fill_super+0x2e8/0xb90 [] get_sb_bdev+0x145/0x180 [] get_super_block+0x21/0x30 [] vfs_kern_mount+0x40/0xd0 [] do_kern_mount+0x39/0xd0 [] do_mount+0x2c7/0x6b0 [] sys_mount+0x66/0xa0 [] mount_block_root+0xc4/0x245 [] mount_root+0x59/0x5f [] prepare_namespace+0x111/0x14b [] kernel_init+0xcf/0xdb [] kernel_thread_helper+0x7/0x1c This is actually fine for two reasons: we call vmalloc at mount time then it's not in the swapping out path. Also the reiserfs lock can be acquired recursively, but since its implementation depends on a mutex, it's hard and not necessary worth it to teach that to lockdep. The lock is useless at mount time anyway, at least until we replay the journal. But let's remove it from this path later as this needs more thinking and is a sensible change. For now we can just relax the lock around vmalloc, Reported-by: Alexander Beregalov Signed-off-by: Frederic Weisbecker Cc: Chris Mason Cc: Ingo Molnar Cc: Thomas Gleixner --- fs/reiserfs/bitmap.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/fs/reiserfs/bitmap.c b/fs/reiserfs/bitmap.c index 685495707181..65c872761177 100644 --- a/fs/reiserfs/bitmap.c +++ b/fs/reiserfs/bitmap.c @@ -1277,7 +1277,10 @@ int reiserfs_init_bitmap_cache(struct super_block *sb) struct reiserfs_bitmap_info *bitmap; unsigned int bmap_nr = reiserfs_bmap_count(sb); + /* Avoid lock recursion in fault case */ + reiserfs_write_unlock(sb); bitmap = vmalloc(sizeof(*bitmap) * bmap_nr); + reiserfs_write_lock(sb); if (bitmap == NULL) return -ENOMEM; -- GitLab