From: Filipe Manana Date: Wed, 14 May 2025 09:30:58 +0000 (+0100) Subject: btrfs: fix wrong start offset for delalloc space release during mmap write X-Git-Tag: block-6.16-20250606~42^2~6 X-Git-Url: https://git.kernel.dk/?a=commitdiff_plain;h=17a85f520469a1838379de8ad24f63e778f7c277;p=linux-block.git btrfs: fix wrong start offset for delalloc space release during mmap write If we're doing a mmap write against a folio that has i_size somewhere in the middle and we have multiple sectors in the folio, we may have to release excess space previously reserved, for the range going from the rounded up (to sector size) i_size to the folio's end offset. We are calculating the right amount to release and passing it to btrfs_delalloc_release_space(), but we are passing the wrong start offset of that range - we're passing the folio's start offset instead of the end offset, plus 1, of the range for which we keep the reservation. This may result in releasing more space then we should and eventually trigger an underflow of the data space_info's bytes_may_use counter. So fix this by passing the start offset as 'end + 1' instead of 'page_start' to btrfs_delalloc_release_space(). Fixes: d0b7da88f640 ("Btrfs: btrfs_page_mkwrite: Reserve space in sectorsized units") Reviewed-by: Qu Wenruo Signed-off-by: Filipe Manana Reviewed-by: David Sterba Signed-off-by: David Sterba --- diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c index 660a73b6af90..32aad1b02b01 100644 --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -1918,7 +1918,7 @@ again: if (reserved_space < fsize) { end = page_start + reserved_space - 1; btrfs_delalloc_release_space(BTRFS_I(inode), - data_reserved, page_start, + data_reserved, end + 1, fsize - reserved_space, true); } }