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Commit ab6e2410 authored by Josef Bacik's avatar Josef Bacik Committed by Chris Mason
Browse files

Btrfs: fix data enospc check overflow 



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: default avatarJosef Bacik <josef@redhat.com>
Signed-off-by: default avatarChris Mason <chris.mason@oracle.com>
parent 109f6aef

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.