Filipe Manana
2014-Aug-08 01:47 UTC
[PATCH] Btrfs: don't monopolize a core when evicting inode
If an inode has a very large number of extent maps, we can spend
a lot of time freeing them, which triggers a soft lockup warning.
Therefore reschedule if we need to when freeing the extent maps
while evicting the inode.
I could trigger this all the time by running xfstests/generic/299 on
a file system with the no-holes feature enabled. That test creates
an inode with 11386677 extent maps.
$ mkfs.btrfs -f -O no-holes $TEST_DEV
$ MKFS_OPTIONS="-O no-holes" ./check generic/299
generic/299 382s ...
Message from syslogd@debian-vm3 at Aug 7 10:44:29 ...
kernel:[85304.208017] BUG: soft lockup - CPU#0 stuck for 22s!
[umount:25330]
384s
Ran: generic/299
Passed all 1 tests
$ dmesg
(...)
[86304.300017] BUG: soft lockup - CPU#0 stuck for 23s! [umount:25330]
(...)
[86304.300036] Call Trace:
[86304.300036] [<ffffffff81698ba9>] __slab_free+0x54/0x295
[86304.300036] [<ffffffffa02ee9cc>] ? free_extent_map+0x5c/0xb0
[btrfs]
[86304.300036] [<ffffffff811a6cd2>] kmem_cache_free+0x282/0x2a0
[86304.300036] [<ffffffffa02ee9cc>] free_extent_map+0x5c/0xb0 [btrfs]
[86304.300036] [<ffffffffa02e3775>] btrfs_evict_inode+0xd5/0x660
[btrfs]
[86304.300036] [<ffffffff811e7c8d>] ?
__inode_wait_for_writeback+0x6d/0xc0
[86304.300036] [<ffffffff816a389b>] ? _raw_spin_unlock+0x2b/0x40
[86304.300036] [<ffffffff811d8cbb>] evict+0xab/0x180
[86304.300036] [<ffffffff811d8dce>] dispose_list+0x3e/0x60
[86304.300036] [<ffffffff811d9b04>] evict_inodes+0xf4/0x110
[86304.300036] [<ffffffff811bd953>] generic_shutdown_super+0x53/0x110
[86304.300036] [<ffffffff811bdaa6>] kill_anon_super+0x16/0x30
[86304.300036] [<ffffffffa02a78ba>] btrfs_kill_super+0x1a/0xa0
[btrfs]
[86304.300036] [<ffffffff811bd3a9>] deactivate_locked_super+0x59/0x80
[86304.300036] [<ffffffff811be44e>] deactivate_super+0x4e/0x70
[86304.300036] [<ffffffff811dec14>] mntput_no_expire+0x174/0x1f0
[86304.300036] [<ffffffff811deab7>] ? mntput_no_expire+0x17/0x1f0
[86304.300036] [<ffffffff811e0517>] SyS_umount+0x97/0x100
(...)
Signed-off-by: Filipe Manana <fdmanana@suse.com>
---
fs/btrfs/inode.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 8ad3ea9..00b4bd3 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -4718,6 +4718,11 @@ static void evict_inode_truncate_pages(struct inode
*inode)
clear_bit(EXTENT_FLAG_LOGGING, &em->flags);
remove_extent_mapping(map_tree, em);
free_extent_map(em);
+ if (need_resched()) {
+ write_unlock(&map_tree->lock);
+ cond_resched();
+ write_lock(&map_tree->lock);
+ }
}
write_unlock(&map_tree->lock);
@@ -4740,6 +4745,7 @@ static void evict_inode_truncate_pages(struct inode
*inode)
&cached_state, GFP_NOFS);
free_extent_state(state);
+ cond_resched();
spin_lock(&io_tree->lock);
}
spin_unlock(&io_tree->lock);
--
1.9.1
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