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 <[email protected]> --- fs/btrfs/extent-tree.c | 20 +++++++++++++++----- 1 files changed, 15 insertions(+), 5 deletions(-) diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index 7bb97de..1860969 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -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. -- 1.6.6 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
