From 4c54659269ecb799133758330e7ea2a6fa4c65ca Mon Sep 17 00:00:00 2001 From: Daeho Jeong Date: Mon, 25 Apr 2016 23:21:00 -0400 Subject: ext4: handle unwritten or delalloc buffers before enabling data journaling 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 Signed-off-by: Theodore Ts'o Reviewed-by: Jan Kara --- fs/ext4/inode.c | 31 ++++++++++++++++++++----------- 1 file changed, 20 insertions(+), 11 deletions(-) (limited to 'fs/ext4/inode.c') diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c index 17bfa42ac971..779ef4c11bc1 100644 --- a/fs/ext4/inode.c +++ b/fs/ext4/inode.c @@ -5452,22 +5452,29 @@ int ext4_change_inode_journal_flag(struct inode *inode, int val) return 0; if (is_journal_aborted(journal)) return -EROFS; - /* We have to allocate physical blocks for delalloc blocks - * before flushing journal. otherwise delalloc blocks can not - * be allocated any more. even more truncate on delalloc blocks - * could trigger BUG by flushing delalloc blocks in journal. - * There is no delalloc block in non-journal data mode. - */ - if (val && test_opt(inode->i_sb, DELALLOC)) { - err = ext4_alloc_da_blocks(inode); - if (err < 0) - return err; - } /* Wait for all existing dio workers */ ext4_inode_block_unlocked_dio(inode); inode_dio_wait(inode); + /* + * Before flushing the journal and switching inode's aops, we have + * to flush all dirty data the inode has. There can be outstanding + * delayed allocations, there can be unwritten extents created by + * fallocate or buffered writes in dioread_nolock mode covered by + * dirty data which can be converted only after flushing the dirty + * data (and journalled aops don't know how to handle these cases). + */ + if (val) { + down_write(&EXT4_I(inode)->i_mmap_sem); + err = filemap_write_and_wait(inode->i_mapping); + if (err < 0) { + up_write(&EXT4_I(inode)->i_mmap_sem); + ext4_inode_resume_unlocked_dio(inode); + return err; + } + } + jbd2_journal_lock_updates(journal); /* @@ -5492,6 +5499,8 @@ int ext4_change_inode_journal_flag(struct inode *inode, int val) ext4_set_aops(inode); jbd2_journal_unlock_updates(journal); + if (val) + up_write(&EXT4_I(inode)->i_mmap_sem); ext4_inode_resume_unlocked_dio(inode); /* Finally we can mark the inode as dirty. */ -- cgit v1.2.3