On Sat, Dec 14, 2013 at 2:56 PM, Shilong Wang <[email protected]> wrote: > Hello Filipe, > > 2013/12/14 Filipe David Borba Manana <[email protected]>: >> Wang Shilong got into a case where during inode eviction we were >> removing an extent map while it was pinned. This triggered a warning >> in remove_extent_mapping() because the extent map had the pinned >> flag set: >> >> [ 1209.102076] [<ffffffffa04721b9>] remove_extent_mapping+0x69/0x70 [btrfs] >> [ 1209.102084] [<ffffffffa0466b06>] btrfs_evict_inode+0x96/0x4d0 [btrfs] >> [ 1209.102089] [<ffffffff81073010>] ? wake_atomic_t_function+0x40/0x40 >> [ 1209.102092] [<ffffffff8118ab2e>] evict+0x9e/0x190 >> [ 1209.102094] [<ffffffff8118b313>] iput+0xf3/0x180 >> [ 1209.102101] [<ffffffffa0461fd1>] btrfs_run_delayed_iputs+0xb1/0xd0 >> [btrfs] >> [ 1209.102107] [<ffffffffa045d358>] __btrfs_end_transaction+0x268/0x350 >> [btrfs] >> >> Therefore wait for any pending ordered extents, if any, which will >> trigger calls to unpin_extent_cache(), before removing the extent maps. >> >> Wang's solution of simply clearing the pinned bit wasn't enough, as after >> unpin_extent_cache() will be called and trigger another WARN_ON() because >> the lookup for the extent map returned NULL. > > Why not in evict_inode_truncate_pages() move remove_extent_mapping() after > clear_extent_bit()?
So, if the pinned bit is set, it means some task will clear it later, via unpin_extent_cache(). And if you look at that function, it has this: write_lock(&tree->lock); em = lookup_extent_mapping(tree, start, len); WARN_ON(!em || em->start != start); And remove_extent_mapping() will remove the em from the rbtree, regardless of its reference count value, therefore triggering that warning above. Does it makes sense? thanks > > Thanks, > Wang >> >> Thanks Wang for finding out this. >> >> Signed-off-by: Filipe David Borba Manana <[email protected]> >> --- >> fs/btrfs/inode.c | 5 +++-- >> 1 file changed, 3 insertions(+), 2 deletions(-) >> >> diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c >> index e889779..c2933fb 100644 >> --- a/fs/btrfs/inode.c >> +++ b/fs/btrfs/inode.c >> @@ -4509,6 +4509,9 @@ static void evict_inode_truncate_pages(struct inode >> *inode) >> ASSERT(inode->i_state & I_FREEING); >> truncate_inode_pages(&inode->i_data, 0); >> >> + /* do we really want it for ->i_nlink > 0 and zero btrfs_root_refs? >> */ >> + btrfs_wait_ordered_range(inode, 0, (u64)-1); >> + >> write_lock(&map_tree->lock); >> while (!RB_EMPTY_ROOT(&map_tree->map)) { >> struct extent_map *em; >> @@ -4566,8 +4569,6 @@ void btrfs_evict_inode(struct inode *inode) >> btrfs_orphan_del(NULL, inode); >> goto no_delete; >> } >> - /* do we really want it for ->i_nlink > 0 and zero btrfs_root_refs? >> */ >> - btrfs_wait_ordered_range(inode, 0, (u64)-1); >> >> if (root->fs_info->log_root_recovering) { >> BUG_ON(test_bit(BTRFS_INODE_HAS_ORPHAN_ITEM, >> -- >> 1.7.9.5 >> >> -- >> 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 -- Filipe David Manana, "Reasonable men adapt themselves to the world. Unreasonable men adapt the world to themselves. That's why all progress depends on unreasonable men." -- 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
