| Message ID | 20240701-b4-rst-updates-v3-5-e0437e1e04a6@kernel.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | btrfs: rst: updates for RAID stripe tree | expand |
On Mon, Jul 01, 2024 at 12:25:19PM +0200, Johannes Thumshirn wrote: > From: Johannes Thumshirn <johannes.thumshirn@wdc.com> > > Don't print tree dump in case a raid-stripe-tree lookup fails. > > Dumping the stripe tree in case of a lookup failure was originally > intended to be a debug feature, but it turned out to be a problem, in case > of i.e. readahead. > I have no objection to the change but I'm curious how readahead triggered this? Is there a problem here, or is it just when there is a problem readahead makes it particularly noisy? Thanks, Josef
On 01.07.24 16:13, Josef Bacik wrote: > On Mon, Jul 01, 2024 at 12:25:19PM +0200, Johannes Thumshirn wrote: >> From: Johannes Thumshirn <johannes.thumshirn@wdc.com> >> >> Don't print tree dump in case a raid-stripe-tree lookup fails. >> >> Dumping the stripe tree in case of a lookup failure was originally >> intended to be a debug feature, but it turned out to be a problem, in case >> of i.e. readahead. >> > > I have no objection to the change but I'm curious how readahead triggered this? > Is there a problem here, or is it just when there is a problem readahead makes > it particularly noisy? Thanks, There still is a bug in conjunction with RST and relocation's readahead. But as I've stated in the cover letter, it is know, trivial to trigger, but I haven't fully root caused it yet. All I can say is, that we're doing a use-after-free triggered by: relocate_data_extent() `-> relocate_file_extent_cluster() `-> relocate_one_folio() `-> page_cache_sync_readahead() `-> read_pages() This most likely comes due to readahead requesting a l2p mapping that RST is unaware of, then splits the read bio (that I can see in my debugging) and the endio handler frees the original bio because of an error while the lower layer block driver still uses it.
diff --git a/fs/btrfs/raid-stripe-tree.c b/fs/btrfs/raid-stripe-tree.c index c5c2f19387ff..20be7d0c52e6 100644 --- a/fs/btrfs/raid-stripe-tree.c +++ b/fs/btrfs/raid-stripe-tree.c @@ -332,10 +332,8 @@ int btrfs_get_raid_extent_offset(struct btrfs_fs_info *fs_info, out: if (ret > 0) ret = -ENOENT; - if (ret && ret != -EIO && !stripe->is_scrub) { - if (IS_ENABLED(CONFIG_BTRFS_DEBUG)) - btrfs_print_tree(leaf, 1); - btrfs_err(fs_info, + if (ret && ret != -EIO) { + btrfs_debug(fs_info, "cannot find raid-stripe for logical [%llu, %llu] devid %llu, profile %s", logical, logical + *length, stripe->dev->devid, btrfs_bg_type_to_raid_name(map_type));