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authorMiao Xie <miaox@cn.fujitsu.com>2011-09-09 17:34:35 +0800
committerDavid Sterba <dsterba@suse.cz>2011-10-20 18:10:49 +0200
commit60d2adbb1e7fee1cb4bc67f70bd0bd8ace7b6c3c (patch)
tree9a3e5f57204cf41bbf998a1873e870110c2ff5f8
parentcfbffc39ac89dbd5197cbeec2599a1128eb928f8 (diff)
Btrfs: fix race between multi-task space allocation and caching space
The task may fail to get free space though it is enough when multi-task space allocation and caching space happen at the same time. Task1 Caching Thread Task2 ------------------------------------------------------------------------ find_free_extent The space has not be cached, and start caching thread. And wait for it. cache space, if the space is > 2MB wake up Task1 find_free_extent get all the space that is cached. try to allocate space, but there is no space now. trigger BUG_ON() The message is following: btrfs allocation failed flags 1, wanted 4096 space_info has 1040187392 free, is not full space_info total=1082130432, used=4096, pinned=41938944, reserved=0, may_use=40828928, readonly=0 block group 12582912 has 8388608 bytes, 0 used 8388608 pinned 0 reserved block group has cluster?: no 0 blocks of free space at or bigger than bytes is block group 1103101952 has 1073741824 bytes, 4096 used 33550336 pinned 0 reserved block group has cluster?: no 0 blocks of free space at or bigger than bytes is ------------[ cut here ]------------ kernel BUG at fs/btrfs/inode.c:835! [<ffffffffa031261b>] __extent_writepage+0x1bf/0x5ce [btrfs] [<ffffffff810cbcb8>] ? __set_page_dirty_nobuffers+0xfe/0x108 [<ffffffffa02f8ada>] ? wait_current_trans+0x23/0xec [btrfs] [<ffffffff810c3fbf>] ? find_get_pages_tag+0x73/0xe2 [<ffffffffa0312d12>] extent_write_cache_pages.clone.0+0x176/0x29a [btrfs] [<ffffffffa0312e74>] extent_writepages+0x3e/0x53 [btrfs] [<ffffffff8110ad2c>] ? do_sync_write+0xc6/0x103 [<ffffffffa0302d6e>] ? btrfs_submit_direct+0x414/0x414 [btrfs] [<ffffffff811380fa>] ? fsnotify+0x236/0x266 [<ffffffffa02fc930>] btrfs_writepages+0x22/0x24 [btrfs] [<ffffffff810cc215>] do_writepages+0x1c/0x25 [<ffffffff810c4958>] __filemap_fdatawrite_range+0x4e/0x50 [<ffffffff810c4982>] filemap_write_and_wait_range+0x28/0x51 [<ffffffffa0306b2e>] btrfs_sync_file+0x7d/0x198 [btrfs] [<ffffffff8110aa26>] ? fsnotify_modify+0x5d/0x65 [<ffffffff8112d150>] vfs_fsync_range+0x18/0x21 [<ffffffff8112d170>] vfs_fsync+0x17/0x19 [<ffffffff8112d316>] do_fsync+0x29/0x3e [<ffffffff8112d348>] sys_fsync+0xb/0xf [<ffffffff81468352>] system_call_fastpath+0x16/0x1b [SNIP] RIP [<ffffffffa02fe08c>] cow_file_range+0x1c4/0x32b [btrfs] We fix this bug by trying to allocate the space again if there are block groups in caching. Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
-rw-r--r--fs/btrfs/extent-tree.c7
1 files changed, 7 insertions, 0 deletions
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 6cfcc9060c83..cef355f1328a 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -4954,6 +4954,7 @@ static noinline int find_free_extent(struct btrfs_trans_handle *trans,
bool failed_cluster_refill = false;
bool failed_alloc = false;
bool use_cluster = true;
+ bool have_caching_bg = false;
u64 ideal_cache_percent = 0;
u64 ideal_cache_offset = 0;
@@ -5036,6 +5037,7 @@ ideal_cache:
}
}
search:
+ have_caching_bg = false;
down_read(&space_info->groups_sem);
list_for_each_entry(block_group, &space_info->block_groups[index],
list) {
@@ -5244,6 +5246,8 @@ refill_cluster:
failed_alloc = true;
goto have_block_group;
} else if (!offset) {
+ if (!cached)
+ have_caching_bg = true;
goto loop;
}
checks:
@@ -5294,6 +5298,9 @@ loop:
}
up_read(&space_info->groups_sem);
+ if (!ins->objectid && loop >= LOOP_CACHING_WAIT && have_caching_bg)
+ goto search;
+
if (!ins->objectid && ++index < BTRFS_NR_RAID_TYPES)
goto search;