Btrfs: fix data enospc check overflow (ab6e2410) · Commits · 戴 / test

Because we account for reserved space we get from the allocator before we actually account for allocating delalloc space, we can have a small window where the amount of "used" space in a space_info is more than the total amount of space in the space_info. This will cause a overflow in our check, so it will seem like we have _tons_ of free space, and we'll allow reservations to occur that will end up larger than the amount of space we have. I've seen users report ENOSPC panic's in cow_file_range a few times recently, so I tried to reproduce this problem and found I could reproduce it if I ran one of my tests in a loop for like 20 minutes. With this patch my test ran all night without issues. Thanks, Signed-off-by:

Josef Bacik <josef@redhat.com> Signed-off-by:

Chris Mason <chris.mason@oracle.com>

fs/btrfs/extent-tree.c

+15 −5

Original line number	Diff line number	Diff line
		@@ -3234,7 +3234,8 @@ int btrfs_check_data_free_space(struct btrfs_root root, struct inode inode,
		u64 bytes)
		{
		struct btrfs_space_info *data_sinfo;
		int ret = 0, committed = 0;
		u64 used;
		int ret = 0, committed = 0, flushed = 0;

		/* make sure bytes are sectorsize aligned */
		bytes = (bytes + root->sectorsize - 1) & ~((u64)root->sectorsize - 1);
		@@ -3246,12 +3247,21 @@ int btrfs_check_data_free_space(struct btrfs_root root, struct inode inode,
		again:
		/* make sure we have enough space to handle the data first */
		spin_lock(&data_sinfo->lock);
		if (data_sinfo->total_bytes - data_sinfo->bytes_used -
		data_sinfo->bytes_delalloc - data_sinfo->bytes_reserved -
		data_sinfo->bytes_pinned - data_sinfo->bytes_readonly -
		data_sinfo->bytes_may_use - data_sinfo->bytes_super < bytes) {
		used = data_sinfo->bytes_used + data_sinfo->bytes_delalloc +
		data_sinfo->bytes_reserved + data_sinfo->bytes_pinned +
		data_sinfo->bytes_readonly + data_sinfo->bytes_may_use +
		data_sinfo->bytes_super;

		if (used + bytes > data_sinfo->total_bytes) {
		struct btrfs_trans_handle *trans;

		if (!flushed) {
		spin_unlock(&data_sinfo->lock);
		flush_delalloc(root, data_sinfo);
		flushed = 1;
		goto again;
		}

		/*
		* if we don't have enough free bytes in this space then we need
		* to alloc a new chunk.

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