On Mon, Apr 07 2008, Jörn Engel wrote: > On Fri, 4 April 2008 13:46:00 +0200, Jens Axboe wrote: > > On Tue, Apr 01 2008, joern@xxxxxxxxx wrote: > > > And it is currently reasonably simple to run into a deadlock when > > > using logfs on a block device. The problem appears to be the block > > > layer allocating memory for its cache without GFP_NOFS, so that under > > > memory pressure logfs writes through block layer may recurse back to > > > logfs writes. > > > > So you mean for writes through the page cache, you are seeing pages > > allocated with __GFP_FS set? > > It sure looks like it. On top, the patch at the bottom seems to solve > the deadlock. I'm just not certain it is the right fix for the problem. > > > > Not entirely sure who is to blame for this bug and how to > > > solve it. > > > > A good starting point would be doing a stack trace dump in logfs if you > > see such back recursion into the fs. A quick guess would be a missing > > setting of mapping gfp mask? > > Sorry, should have sent that right along. > > [<ffffffff802ca83f>] elv_insert+0x156/0x219 > [<ffffffff8037d96d>] __mutex_lock_slowpath+0x57/0x81 > [<ffffffff8037d804>] mutex_lock+0xd/0xf > [<ffffffff802c07e7>] logfs_get_wblocks+0x33/0x54 > [<ffffffff802c025c>] logfs_write_buf+0x3d/0x322 > [<ffffffff802bbae0>] __logfs_writepage+0x24/0x67 > [<ffffffff802bbbfb>] logfs_writepage+0xd8/0xe3 > [<ffffffff8024ba78>] shrink_page_list+0x2ee/0x514 > [<ffffffff8024b466>] isolate_lru_pages+0x6c/0x1ff > [<ffffffff8024c2a9>] shrink_zone+0x60b/0x85b > [<ffffffff802cc0e5>] generic_make_request+0x329/0x364 > [<ffffffff80245ea1>] mempool_alloc_slab+0x11/0x13 > [<ffffffff802367b3>] up_read+0x9/0xb > [<ffffffff8024c638>] shrink_slab+0x13f/0x151 > [<ffffffff8024cc1c>] try_to_free_pages+0x111/0x209 > [<ffffffff8024859a>] __alloc_pages+0x1b1/0x2f5 > [<ffffffff80243f6b>] read_cache_page_async+0x7e/0x15c > [<ffffffff8027fba9>] blkdev_readpage+0x0/0x15 > [<ffffffff80245612>] read_cache_page+0xe/0x46 > [<ffffffff802c2842>] bdev_read+0x61/0xee > [<ffffffff802bc741>] __logfs_gc_pass+0x219/0x7dc > [<ffffffff802bcd1b>] logfs_gc_pass+0x17/0x19 > [<ffffffff802c0798>] logfs_flush_dirty+0x7d/0x99 > [<ffffffff802c0800>] logfs_get_wblocks+0x4c/0x54 > [<ffffffff802c025c>] logfs_write_buf+0x3d/0x322 > [<ffffffff802bbe1e>] logfs_commit_write+0x77/0x7d > [<ffffffff80244ec2>] generic_file_buffered_write+0x49d/0x62c > [<ffffffff802704da>] file_update_time+0x7f/0xad > [<ffffffff802453a5>] __generic_file_aio_write_nolock+0x354/0x3be > [<ffffffff80237077>] atomic_notifier_call_chain+0xf/0x11 > [<ffffffff80245abb>] filemap_fault+0x1b4/0x320 > [<ffffffff80245473>] generic_file_aio_write+0x64/0xc0 > [<ffffffff8025ebc8>] do_sync_write+0xe2/0x126 > [<ffffffff80224b4f>] release_console_sem+0x1a0/0x1a9 > [<ffffffff802344f4>] autoremove_wake_function+0x0/0x38 > [<ffffffff802ef6f3>] tty_write+0x1f2/0x20d > [<ffffffff802f1914>] write_chan+0x0/0x334 > [<ffffffff8025f351>] vfs_write+0xae/0x137 > [<ffffffff8025f824>] sys_write+0x47/0x6f > [<ffffffff802191c2>] ia32_sysret+0x0/0xa > > Jörn > > -- > Joern's library part 10: > http://blogs.msdn.com/David_Gristwood/archive/2004/06/24/164849.aspx > > Signed-off-by: Joern Engel <joern@xxxxxxxxx> > > fs/block_dev.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > --- linux-2.6.24logfs/fs/block_dev.c~blockdev_nofs 2008-04-07 10:19:08.627413077 +0200 > +++ linux-2.6.24logfs/fs/block_dev.c 2008-04-07 10:20:56.927117162 +0200 > @@ -586,7 +586,7 @@ struct block_device *bdget(dev_t dev) > inode->i_rdev = dev; > inode->i_bdev = bdev; > inode->i_data.a_ops = &def_blk_aops; > - mapping_set_gfp_mask(&inode->i_data, GFP_USER); > + mapping_set_gfp_mask(&inode->i_data, GFP_USER & ~__GFP_FS); > inode->i_data.backing_dev_info = &default_backing_dev_info; > spin_lock(&bdev_lock); > list_add(&bdev->bd_list, &all_bdevs); It's not the right fix, generally GFP_FS is fine here. So do that in logfs when you cannot traverse back into the fs, eg mapping_gfp_mask(mapping) & ~__GFP_FS; locally. -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
