The quilt patch titled Subject: buffer: fix unintended successful return has been removed from the -mm tree. Its filename was buffer-fix-unintended-successful-return.patch This patch was dropped because it was merged into the mm-stable branch of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm ------------------------------------------------------ From: "Matthew Wilcox (Oracle)" <willy@xxxxxxxxxxxxx> Subject: buffer: fix unintended successful return Date: Mon, 1 Jan 2024 09:38:48 +0000 If try_to_free_buffers() succeeded and then folio_alloc_buffers() failed, grow_dev_folio() would return success. This would be incorrect; memory allocation failure is supposed to result in a failure. It's a harmless bug; the caller will simply go around the loop one more time and grow_dev_folio() will correctly return a failure that time. But it was an unintended change and looks like a more serious bug than it is. While I'm in here, improve the commentary about why we return success even though we failed. Link: https://lkml.kernel.org/r/20240101093848.2017115-1-willy@xxxxxxxxxxxxx Fixes: 6d840a18773f ("buffer: return bool from grow_dev_folio()") Signed-off-by: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx> Reported-by: Ryusuke Konishi <konishi.ryusuke@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- fs/buffer.c | 17 ++++++++++++----- 1 file changed, 12 insertions(+), 5 deletions(-) --- a/fs/buffer.c~buffer-fix-unintended-successful-return +++ a/fs/buffer.c @@ -1028,8 +1028,8 @@ static sector_t folio_init_buffers(struc * * This is used purely for blockdev mappings. * - * Returns false if we have a 'permanent' failure. Returns true if - * we succeeded, or the caller should retry. + * Returns false if we have a failure which cannot be cured by retrying + * without sleeping. Returns true if we succeeded, or the caller should retry. */ static bool grow_dev_folio(struct block_device *bdev, sector_t block, pgoff_t index, unsigned size, gfp_t gfp) @@ -1051,10 +1051,17 @@ static bool grow_dev_folio(struct block_ goto unlock; } - /* Caller should retry if this call fails */ - end_block = ~0ULL; - if (!try_to_free_buffers(folio)) + /* + * Retrying may succeed; for example the folio may finish + * writeback, or buffers may be cleaned. This should not + * happen very often; maybe we have old buffers attached to + * this blockdev's page cache and we're trying to change + * the block size? + */ + if (!try_to_free_buffers(folio)) { + end_block = ~0ULL; goto unlock; + } } bh = folio_alloc_buffers(folio, size, gfp | __GFP_ACCOUNT); _ Patches currently in -mm which might be from willy@xxxxxxxxxxxxx are