btrfs: log csums for all modified extents (8c6c5928) · Commits · 戴 / test

Amir reported a bug discovered by his cleaned up version of my dm-log-writes xfstests where we were missing csums at certain replay points. This is because fsx was doing an msync(), which essentially fsync()'s a specific range of a file. We will log all modified extents, but only search for the checksums in the range we are being asked to sync. We cannot simply log the extents in the range we're being asked because we are logging the inode item as it is currently, which if it has had a i_size update before the msync means we will miss extents when replaying. We could possibly get around this by marking the inode with the transaction that extended the i_size to see if we have this case, but this would be racy and we'd have to lock the whole range of the inode to make sure we didn't have an ordered extent outside of our range that was in the middle of completing. Fix this simply by keeping track of the modified extents range and logging the csums for the entire range of extents that we are logging. This makes the xfstest pass. Reported-by:

Amir Goldstein <amir73il@gmail.com> Signed-off-by:

Josef Bacik <jbacik@fb.com> Signed-off-by:

David Sterba <dsterba@suse.com>

fs/btrfs/tree-log.c

+10 −2

Original line number	Diff line number	Diff line
		@@ -4181,6 +4181,7 @@ static int btrfs_log_changed_extents(struct btrfs_trans_handle *trans,
		struct extent_map em, n;
		struct list_head extents;
		struct extent_map_tree *tree = &inode->extent_tree;
		u64 logged_start, logged_end;
		u64 test_gen;
		int ret = 0;
		int num = 0;
		@@ -4190,10 +4191,11 @@ static int btrfs_log_changed_extents(struct btrfs_trans_handle *trans,
		down_write(&inode->dio_sem);
		write_lock(&tree->lock);
		test_gen = root->fs_info->last_trans_committed;
		logged_start = start;
		logged_end = end;

		list_for_each_entry_safe(em, n, &tree->modified_extents, list) {
		list_del_init(&em->list);

		/*
		* Just an arbitrary number, this can be really CPU intensive
		* once we start getting a lot of extents, and really once we
		@@ -4208,6 +4210,12 @@ static int btrfs_log_changed_extents(struct btrfs_trans_handle *trans,

		if (em->generation <= test_gen)
		continue;

		if (em->start < logged_start)
		logged_start = em->start;
		if ((em->start + em->len - 1) > logged_end)
		logged_end = em->start + em->len - 1;

		/* Need a ref to keep it from getting evicted from cache */
		refcount_inc(&em->refs);
		set_bit(EXTENT_FLAG_LOGGING, &em->flags);
		@@ -4216,7 +4224,7 @@ static int btrfs_log_changed_extents(struct btrfs_trans_handle *trans,
		}

		list_sort(NULL, &extents, extent_cmp);
		btrfs_get_logged_extents(inode, logged_list, start, end);
		btrfs_get_logged_extents(inode, logged_list, logged_start, logged_end);
		/*
		* Some ordered extents started by fsync might have completed
		* before we could collect them into the list logged_list, which

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