On Tue, Dec 04, 2018 at 02:48:18PM +0200, Nikolay Borisov wrote:
When a metadata read is served the endio routine btree_readpage_end_io_hook is called which eventually runs the tree-checker. If tree-checker fails to validate the read eb then it sets EXTENT_BUFFER_CORRUPT flag. This leads to btree_read_extent_buffer_pages wrongly assuming that all available copies of this extent buffer are wrong and failing prematurely. Fix this modify btree_read_extent_buffer_pages to read all copies of the data.
This failure was exhibitted in xfstests btrfs/124 which would spuriously fail its balance operations. The reason was that when balance was run following re-introduction of the missing raid1 disk __btrfs_map_block would map the read request to stripe 0, which corresponded to devid 2 (the disk which is being removed in the test):
item 2 key (FIRST_CHUNK_TREE CHUNK_ITEM 3553624064) itemoff 15975 itemsize 112length 1073741824 owner 2 stripe_len 65536 type DATA|RAID1 io_align 65536 io_width 65536 sector_size 4096 num_stripes 2 sub_stripes 1 stripe 0 devid 2 offset 2156920832 dev_uuid 8466c350-ed0c-4c3b-b17d-6379b445d5c8 stripe 1 devid 1 offset 3553624064 dev_uuid 1265d8db-5596-477e-af03-df08eb38d2ca
This caused read requests for a checksum item that to be routed to the stale disk which triggered the aforementioned logic involving EXTENT_BUFFER_CORRUPT flag. This then triggered cascading failures of the balance operation.
Fixes: a826d6dcb32d ("Btrfs: check items for correctness as we search") CC: stable@vger.kernel.org # 4.4+ Suggested-by: Qu Wenruo wqu@suse.com Reviewed-by: Qu Wenruo wqu@suse.com Signed-off-by: Nikolay Borisov nborisov@suse.com Signed-off-by: David Sterba dsterba@suse.com
Hi Gregk,
Please apply this backport of upstream commit f8397d69daef06d358430d3054662fb597e37c00 to 4.9.y
I think this was the 4.14.y version of the patch :(
I took the 4.4.y version and fixed it up by hand...
greg k-h