@@ -2486,6 +2486,16 @@ static int btrfs_punch_hole_lock_range(struct inode *inode,
const u64 lockend,
struct extent_state **cached_state)
{
+ /*
+ * For subpage case, if the range is not at page boundary, we could
+ * have pages at the leading/tailing part of the range.
+ * This could lead to dead loop since filemap_range_has_page()
+ * will always return true.
+ * So here we need to do extra page alignment for
+ * filemap_range_has_page().
+ */
+ u64 page_lockstart = round_up(lockstart, PAGE_SIZE);
+ u64 page_lockend = round_down(lockend + 1, PAGE_SIZE) - 1;
while (1) {
struct btrfs_ordered_extent *ordered;
int ret;
@@ -2506,7 +2516,7 @@ static int btrfs_punch_hole_lock_range(struct inode *inode,
(ordered->file_offset + ordered->num_bytes <= lockstart ||
ordered->file_offset > lockend)) &&
!filemap_range_has_page(inode->i_mapping,
- lockstart, lockend)) {
+ page_lockstart, page_lockend)) {
if (ordered)
btrfs_put_ordered_extent(ordered);
break;
[BUG] With current subpage RW support, the following script can hang the fs on with 64K page size. # mkfs.btrfs -f -s 4k $dev # mount $dev -o nospace_cache $mnt # fsstress -w -n 50 -p 1 -s 1607749395 -d $mnt The kernel will do an infinite loop in btrfs_punch_hole_lock_range(). [CAUSE] In btrfs_punch_hole_lock_range() we: - Truncate page cache range - Lock extent io tree - Wait any ordered extents in the range. We exit the loop until we meet all the following conditions: - No ordered extent in the lock range - No page is in the lock range The latter condition has a pitfall, it only works for sector size == PAGE_SIZE case. While can't handle the following subpage case: 0 32K 64K 96K 128K | |///////||//////| || lockstart=32K lockend=96K - 1 In this case, although the range cross 2 pages, truncate_pagecache_range() will invalidate no page at all, but only zero the [32K, 96K) range of the two pages. Thus filemap_range_has_page(32K, 96K-1) will always return true, thus we will never meet the loop exit condition. [FIX] Fix the problem by doing page alignment for the lock range. Function filemap_range_has_page() has already handled lend < lstart case, we only need to round up @lockstart, and round_down @lockend for truncate_pagecache_range(). This modification should not change any thing for sector size == PAGE_SIZE case, as in that case our range is already page aligned. Signed-off-by: Qu Wenruo <wqu@suse.com> --- fs/btrfs/file.c | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-)