Hello Filipe,
2013/12/14 Filipe David Borba Manana <fdmanana@xxxxxxxxx>:
> 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()?
Thanks,
Wang
>
> Thanks Wang for finding out this.
>
> Signed-off-by: Filipe David Borba Manana <fdmanana@xxxxxxxxx>
> ---
> 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
>
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