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: Josef Bacik <josef@redhat.com> Signed-off-by: Chris Mason <chris.mason@oracle.com>
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@ -3234,7 +3234,8 @@ int btrfs_check_data_free_space(struct btrfs_root *root, struct inode *inode,
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u64 bytes)
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{
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struct btrfs_space_info *data_sinfo;
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int ret = 0, committed = 0;
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u64 used;
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int ret = 0, committed = 0, flushed = 0;
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/* make sure bytes are sectorsize aligned */
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bytes = (bytes + root->sectorsize - 1) & ~((u64)root->sectorsize - 1);
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@ -3246,12 +3247,21 @@ int btrfs_check_data_free_space(struct btrfs_root *root, struct inode *inode,
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again:
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/* make sure we have enough space to handle the data first */
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spin_lock(&data_sinfo->lock);
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if (data_sinfo->total_bytes - data_sinfo->bytes_used -
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data_sinfo->bytes_delalloc - data_sinfo->bytes_reserved -
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data_sinfo->bytes_pinned - data_sinfo->bytes_readonly -
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data_sinfo->bytes_may_use - data_sinfo->bytes_super < bytes) {
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used = data_sinfo->bytes_used + data_sinfo->bytes_delalloc +
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data_sinfo->bytes_reserved + data_sinfo->bytes_pinned +
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data_sinfo->bytes_readonly + data_sinfo->bytes_may_use +
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data_sinfo->bytes_super;
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if (used + bytes > data_sinfo->total_bytes) {
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struct btrfs_trans_handle *trans;
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if (!flushed) {
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spin_unlock(&data_sinfo->lock);
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flush_delalloc(root, data_sinfo);
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flushed = 1;
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goto again;
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}
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/*
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* if we don't have enough free bytes in this space then we need
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* to alloc a new chunk.
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