-
Daeho Jeong authored
We already allocate delalloc blocks before changing the inode mode into "per-file data journal" mode to prevent delalloc blocks from remaining not allocated, but another issue concerned with "BH_Unwritten" status still exists. For example, by fallocate(), several buffers' status change into "BH_Unwritten", but these buffers cannot be processed by ext4_alloc_da_blocks(). So, they still remain in unwritten status after per-file data journaling is enabled and they cannot be changed into written status any more and, if they are journaled and eventually checkpointed, these unwritten buffer will cause a kernel panic by the below BUG_ON() function of submit_bh_wbc() when they are submitted during checkpointing. static int submit_bh_wbc(int rw, struct buffer_head *bh,... { ... BUG_ON(buffer_unwritten(bh)); Moreover, when "dioread_nolock" option is enabled, the status of a buffer is changed into "BH_Unwritten" after write_begin() completes and the "BH_Unwritten" status will be cleared after I/O is done. Therefore, if a buffer's status is changed into unwrutten but the buffer's I/O is not submitted and completed, it can cause the same problem after enabling per-file data journaling. You can easily generate this bug by executing the following command. ./kvm-xfstests -C 10000 -m nodelalloc,dioread_nolock generic/269 To resolve these problems and define a boundary between the previous mode and per-file data journaling mode, we need to flush and wait all the I/O of buffers of a file before enabling per-file data journaling of the file. Signed-off-by:
Daeho Jeong <daeho.jeong@samsung.com> Signed-off-by:
Theodore Ts'o <tytso@mit.edu> Reviewed-by:
Jan Kara <jack@suse.cz>
4c546592