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authorMiao Xie <miaox@cn.fujitsu.com>2012-02-16 15:01:24 +0800
committerDavid Sterba <dsterba@suse.cz>2012-02-16 17:23:16 +0100
commit600a45e1d5e376f679ff9ecc4ce9452710a6d27c (patch)
treec4bf84eee1db132b5ff18700b95da8426a909f2f
parent013bd4c336ad0d30e9e41f9cff0dbc1858934e75 (diff)
downloadop-kernel-dev-600a45e1d5e376f679ff9ecc4ce9452710a6d27c.zip
op-kernel-dev-600a45e1d5e376f679ff9ecc4ce9452710a6d27c.tar.gz
Btrfs: fix deadlock on page lock when doing auto-defragment
When I ran xfstests circularly on a auto-defragment btrfs, the deadlock happened. Steps to reproduce: [tty0] # export MOUNT_OPTIONS="-o autodefrag" # export TEST_DEV=<partition1> # export TEST_DIR=<mountpoint1> # export SCRATCH_DEV=<partition2> # export SCRATCH_MNT=<mountpoint2> # while [ 1 ] > do > ./check 091 127 263 > sleep 1 > done [tty1] # while [ 1 ] > do > echo 3 > /proc/sys/vm/drop_caches > done Several hours later, the test processes will hang on, and the deadlock will happen on page lock. The reason is that: Auto defrag task Flush thread Test task btrfs_writepages() add ordered extent (including page 1, 2) set page 1 writeback set page 2 writeback endio_fn() end page 2 writeback release page 2 lock page 1 alloc and lock page 2 page 2 is not uptodate btrfs_readpage() start ordered extent() btrfs_writepages() try to lock page 1 so deadlock happens. Fix this bug by unlocking the page which is in writeback, and re-locking it after the writeback end. Signed-off-by: Miao Xie <miax@cn.fujitsu.com>
-rw-r--r--fs/btrfs/ioctl.c53
1 files changed, 29 insertions, 24 deletions
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 0b06a5c..e9bdb8b 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -862,6 +862,7 @@ static int cluster_pages_for_defrag(struct inode *inode,
int i_done;
struct btrfs_ordered_extent *ordered;
struct extent_state *cached_state = NULL;
+ struct extent_io_tree *tree;
gfp_t mask = btrfs_alloc_write_mask(inode->i_mapping);
if (isize == 0)
@@ -872,18 +873,34 @@ static int cluster_pages_for_defrag(struct inode *inode,
num_pages << PAGE_CACHE_SHIFT);
if (ret)
return ret;
-again:
- ret = 0;
i_done = 0;
+ tree = &BTRFS_I(inode)->io_tree;
/* step one, lock all the pages */
for (i = 0; i < num_pages; i++) {
struct page *page;
+again:
page = find_or_create_page(inode->i_mapping,
- start_index + i, mask);
+ start_index + i, mask);
if (!page)
break;
+ page_start = page_offset(page);
+ page_end = page_start + PAGE_CACHE_SIZE - 1;
+ while (1) {
+ lock_extent(tree, page_start, page_end, GFP_NOFS);
+ ordered = btrfs_lookup_ordered_extent(inode,
+ page_start);
+ unlock_extent(tree, page_start, page_end, GFP_NOFS);
+ if (!ordered)
+ break;
+
+ unlock_page(page);
+ btrfs_start_ordered_extent(inode, ordered, 1);
+ btrfs_put_ordered_extent(ordered);
+ lock_page(page);
+ }
+
if (!PageUptodate(page)) {
btrfs_readpage(NULL, page);
lock_page(page);
@@ -894,15 +911,22 @@ again:
break;
}
}
+
isize = i_size_read(inode);
file_end = (isize - 1) >> PAGE_CACHE_SHIFT;
- if (!isize || page->index > file_end ||
- page->mapping != inode->i_mapping) {
+ if (!isize || page->index > file_end) {
/* whoops, we blew past eof, skip this page */
unlock_page(page);
page_cache_release(page);
break;
}
+
+ if (page->mapping != inode->i_mapping) {
+ unlock_page(page);
+ page_cache_release(page);
+ goto again;
+ }
+
pages[i] = page;
i_done++;
}
@@ -925,25 +949,6 @@ again:
lock_extent_bits(&BTRFS_I(inode)->io_tree,
page_start, page_end - 1, 0, &cached_state,
GFP_NOFS);
- ordered = btrfs_lookup_first_ordered_extent(inode, page_end - 1);
- if (ordered &&
- ordered->file_offset + ordered->len > page_start &&
- ordered->file_offset < page_end) {
- btrfs_put_ordered_extent(ordered);
- unlock_extent_cached(&BTRFS_I(inode)->io_tree,
- page_start, page_end - 1,
- &cached_state, GFP_NOFS);
- for (i = 0; i < i_done; i++) {
- unlock_page(pages[i]);
- page_cache_release(pages[i]);
- }
- btrfs_wait_ordered_range(inode, page_start,
- page_end - page_start);
- goto again;
- }
- if (ordered)
- btrfs_put_ordered_extent(ordered);
-
clear_extent_bit(&BTRFS_I(inode)->io_tree, page_start,
page_end - 1, EXTENT_DIRTY | EXTENT_DELALLOC |
EXTENT_DO_ACCOUNTING, 0, 0, &cached_state,
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