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Commitdbfdb6d1b3("Btrfs: Search for all ordered extents that could span across a page") make btrfs_invalidapage() to search all ordered extents. The offending code looks like this: again: start = page_start; ordered = btrfs_lookup_ordered_range(inode, start, page_end - start + 1); if (ordred) { end = min(page_end, ordered->file_offset + ordered->num_bytes - 1); /* Do the cleanup */ start = end + 1; if (start < page_end) goto again; } The behavior is indeed necessary for the incoming subpage support, but when it iterates through all the ordered extents, it also resets the search range @start. This means, for the following cases, we can double account the ordered extents, causing its bytes_left underflow: Page offset 0 16K 32K |<--- OE 1 --->|<--- OE 2 ---->| As the first iteration will find ordered extent (OE) 1, which doesn't cover the full page, thus after cleanup code, we need to retry again. But again label will reset start to page_start, and we got OE 1 again, which causes double accounting on OE 1, and cause OE 1's byte_left to underflow. This problem can only happen for subpage case, as for regular sectorsize == PAGE_SIZE case, we will always find a OE ends at or after page end, thus no way to trigger the problem. Move the again label after start = page_start. There will be more comprehensive rework to convert the open coded loop to a proper while loop for subpage support. Fixes:dbfdb6d1b3("Btrfs: Search for all ordered extents that could span across a page") Reviewed-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: Qu Wenruo <wqu@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.