On Mon, Feb 12, 2024 at 03:46:15PM +1030, Qu Wenruo wrote: > [BUG] > There is a bug report that with zoned device and sectorsize is smaller > than page size (aka, subpage), btrfs would crash with a very basic > workload: > > # getconfig PAGESIZE > 16384 > # mkfs.btrfs -f $dev -s 4k > # mount $dev $mnt > # $fsstress -w -n 8 -s 1707820327 -v -d $mnt > # umount $mnt > > The crash would look like this (with CONFIG_BTRFS_ASSERT enabled): > > assertion failed: block_start != EXTENT_MAP_HOLE, in fs/btrfs/extent_io.c:1384 This is the same as what Josef fixed in https://github.com/btrfs/linux/commit/400bb013912dac637c7d6826407be580ea8ef9cc "btrfs: don't drop extent_map for free space inode on write error" but not on zoned+subpage, is it really a different error you're fixing? [...] > [WORKAROUND] > A proper fix requires some big changes to delalloc workload, to allow > extent_write_locked_range() to handle multiple different entries with > the same @locked_page. > > So for now, disable read-write support for subpage zoned btrfs. > > The problem can only be solved if subpage btrfs can handle subpage > compression, which need quite some work on the delalloc procedure for > the @locked_page handling. Ok, this on itself is a valid reason to disable the support.
