From 459efa346874a11b4911809e75d6eee157792ca5 Mon Sep 17 00:00:00 2001 From: "Darrick J. Wong" Date: Wed, 11 Jun 2025 09:43:45 -0700 Subject: [PATCH] libext2fs: fix spurious warnings from fallocate generic/522 routinely produces error messages from fuse2fs like this: FUSE2FS (sde): Illegal block number passed to ext2fs_test_block_bitmap #9321 for block bitmap for /dev/sde Curiously, these don't actually result in errors being thrown up to the kernel. Digging into the program (which was more difficult than it needed to be because of the weird bitmap base + errcode weirdness) produced a left record: e_lblk = 16 e_pblk = 9293 e_len = 6 e_flags = 0 and a right record: e_lblk = 45 e_pblk = 9321 e_len = 6 e_flags = 0 Thus we end up in the "Merge both extents together, perhaps?" section of ext_falloc_helper. Unfortunately, the merge selection code isn't smart enough to notice that the two mappings aren't actually physically contiguous, so it scans the bitmap with a negative length, which is why the assertion trips. The simple fix here is not to try to merge the adjacent extents if they're not actually physically contiguous. Cc: linux-ext4@vger.kernel.org # v1.43 Fixes: 5aad5b8e0e3cfa ("libext2fs: implement fallocate") Signed-off-by: Darrick J. Wong Signed-off-by: Theodore Ts'o --- lib/ext2fs/fallocate.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/lib/ext2fs/fallocate.c b/lib/ext2fs/fallocate.c index 5cde7d5c2..063242c5f 100644 --- a/lib/ext2fs/fallocate.c +++ b/lib/ext2fs/fallocate.c @@ -276,6 +276,11 @@ try_merge: max_uninit_len : max_init_len)) goto try_left; + /* Would they even be physically contiguous if merged? */ + if (left_ext->e_pblk + left_ext->e_len + range_len != + right_ext->e_pblk) + goto try_left; + err = ext2fs_extent_goto(handle, left_ext->e_lblk); if (err) goto try_left; -- 2.47.2