6.8-stable review patch. If anyone has any objections, please let me know.
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From: Sweet Tea Dorminy sweettea-kernel@dorminy.me
commit 131a821a243f89be312ced9e62ccc37b2cf3846c upstream.
In commit b4ccace878f4 ("btrfs: refactor submit_compressed_extents()"), if an async extent compressed but failed to find enough space, we changed from falling back to an uncompressed write to just failing the write altogether. The principle was that if there's not enough space to write the compressed version of the data, there can't possibly be enough space to write the larger, uncompressed version of the data.
However, this isn't necessarily true: due to fragmentation, there could be enough discontiguous free blocks to write the uncompressed version, but not enough contiguous free blocks to write the smaller but unsplittable compressed version.
This has occurred to an internal workload which relied on write()'s return value indicating there was space. While rare, it has happened a few times.
Thus, in order to prevent early ENOSPC, re-add a fallback to uncompressed writing.
Fixes: b4ccace878f4 ("btrfs: refactor submit_compressed_extents()") CC: stable@vger.kernel.org # 6.1+ Reviewed-by: Qu Wenruo wqu@suse.com Co-developed-by: Neal Gompa neal@gompa.dev Signed-off-by: Neal Gompa neal@gompa.dev Signed-off-by: Sweet Tea Dorminy sweettea-kernel@dorminy.me Reviewed-by: David Sterba dsterba@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- fs/btrfs/inode.c | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-)
--- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -1144,13 +1144,13 @@ static void submit_one_async_extent(stru 0, *alloc_hint, &ins, 1, 1); if (ret) { /* - * Here we used to try again by going back to non-compressed - * path for ENOSPC. But we can't reserve space even for - * compressed size, how could it work for uncompressed size - * which requires larger size? So here we directly go error - * path. + * We can't reserve contiguous space for the compressed size. + * Unlikely, but it's possible that we could have enough + * non-contiguous space for the uncompressed size instead. So + * fall back to uncompressed. */ - goto out_free; + submit_uncompressed_range(inode, async_extent, locked_page); + goto done; }
/* Here we're doing allocation and writeback of the compressed pages */ @@ -1202,7 +1202,6 @@ done: out_free_reserve: btrfs_dec_block_group_reservations(fs_info, ins.objectid); btrfs_free_reserved_extent(fs_info, ins.objectid, ins.offset, 1); -out_free: mapping_set_error(inode->vfs_inode.i_mapping, -EIO); extent_clear_unlock_delalloc(inode, start, end, NULL, EXTENT_LOCKED | EXTENT_DELALLOC |