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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 <daeho.jeong@samsung.com> Signed-off-by: Theodore Ts'o <tytso@mit.edu> Reviewed-by: Jan Kara <jack@suse.cz>
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@ -5452,22 +5452,29 @@ int ext4_change_inode_journal_flag(struct inode *inode, int val)
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return 0;
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if (is_journal_aborted(journal))
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return -EROFS;
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/* We have to allocate physical blocks for delalloc blocks
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* before flushing journal. otherwise delalloc blocks can not
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* be allocated any more. even more truncate on delalloc blocks
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* could trigger BUG by flushing delalloc blocks in journal.
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* There is no delalloc block in non-journal data mode.
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*/
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if (val && test_opt(inode->i_sb, DELALLOC)) {
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err = ext4_alloc_da_blocks(inode);
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if (err < 0)
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return err;
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}
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/* Wait for all existing dio workers */
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ext4_inode_block_unlocked_dio(inode);
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inode_dio_wait(inode);
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/*
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* Before flushing the journal and switching inode's aops, we have
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* to flush all dirty data the inode has. There can be outstanding
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* delayed allocations, there can be unwritten extents created by
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* fallocate or buffered writes in dioread_nolock mode covered by
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* dirty data which can be converted only after flushing the dirty
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* data (and journalled aops don't know how to handle these cases).
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*/
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if (val) {
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down_write(&EXT4_I(inode)->i_mmap_sem);
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err = filemap_write_and_wait(inode->i_mapping);
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if (err < 0) {
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up_write(&EXT4_I(inode)->i_mmap_sem);
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ext4_inode_resume_unlocked_dio(inode);
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return err;
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}
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}
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jbd2_journal_lock_updates(journal);
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/*
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@ -5492,6 +5499,8 @@ int ext4_change_inode_journal_flag(struct inode *inode, int val)
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ext4_set_aops(inode);
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jbd2_journal_unlock_updates(journal);
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if (val)
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up_write(&EXT4_I(inode)->i_mmap_sem);
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ext4_inode_resume_unlocked_dio(inode);
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/* Finally we can mark the inode as dirty. */
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