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Btrfs: fix data enospc check overflow

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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>
This commit is contained in:
Josef Bacik 2010-03-19 14:38:13 +00:00 committed by Chris Mason
parent 109f6aef5f
commit ab6e24103c
1 changed files with 15 additions and 5 deletions
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20
fs/btrfs/extent-tree.c
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@ -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.