From 15cecdea2066fd94f6b305fe9b1e4f290045293a Mon Sep 17 00:00:00 2001 From: Johannes Thumshirn Date: Wed, 24 Apr 2024 09:37:34 +0200 Subject: [PATCH] btrfs: don't hold dev_replace rwsem over whole of btrfs_map_block Don't hold the dev_replace rwsem for the entirety of btrfs_map_block(). It is only needed to protect: a) calls to find_live_mirror() and b) calling into handle_ops_on_dev_replace(). But there is no need to hold the rwsem for any kind of set_io_stripe() calls. So relax taking the dev_replace rwsem to only protect both cases and check if the device replace status has changed in the meantime, for which we have to re-do the find_live_mirror() calls. This fixes a deadlock on raid-stripe-tree where device replace performs a scrub operation, which in turn calls into btrfs_map_block() to find the physical location of the block. Reviewed-by: Josef Bacik Reviewed-by: Qu Wenruo Reviewed-by: Filipe Manana Signed-off-by: Johannes Thumshirn Signed-off-by: David Sterba --- fs/btrfs/volumes.c | 29 ++++++++++++++++++----------- 1 file changed, 18 insertions(+), 11 deletions(-) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index fcedc43ef291a2..9437e779d02059 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -6650,14 +6650,9 @@ int btrfs_map_block(struct btrfs_fs_info *fs_info, enum btrfs_map_op op, max_len = btrfs_max_io_len(map, map_offset, &io_geom); *length = min_t(u64, map->chunk_len - map_offset, max_len); +again: down_read(&dev_replace->rwsem); dev_replace_is_ongoing = btrfs_dev_replace_is_ongoing(dev_replace); - /* - * Hold the semaphore for read during the whole operation, write is - * requested at commit time but must wait. - */ - if (!dev_replace_is_ongoing) - up_read(&dev_replace->rwsem); switch (map->type & BTRFS_BLOCK_GROUP_PROFILE_MASK) { case BTRFS_BLOCK_GROUP_RAID0: @@ -6695,6 +6690,7 @@ int btrfs_map_block(struct btrfs_fs_info *fs_info, enum btrfs_map_op op, "stripe index math went horribly wrong, got stripe_index=%u, num_stripes=%u", io_geom.stripe_index, map->num_stripes); ret = -EINVAL; + up_read(&dev_replace->rwsem); goto out; } @@ -6710,6 +6706,8 @@ int btrfs_map_block(struct btrfs_fs_info *fs_info, enum btrfs_map_op op, */ num_alloc_stripes += 2; + up_read(&dev_replace->rwsem); + /* * If this I/O maps to a single device, try to return the device and * physical block information on the stack instead of allocating an @@ -6782,6 +6780,19 @@ int btrfs_map_block(struct btrfs_fs_info *fs_info, enum btrfs_map_op op, goto out; } + /* + * Check if something changed the dev_replace state since + * we've checked it for the last time and if redo the whole + * mapping operation. + */ + down_read(&dev_replace->rwsem); + if (dev_replace_is_ongoing != + btrfs_dev_replace_is_ongoing(dev_replace)) { + btrfs_put_bioc(bioc); + up_read(&dev_replace->rwsem); + goto again; + } + if (op != BTRFS_MAP_READ) io_geom.max_errors = btrfs_chunk_max_errors(map); @@ -6789,6 +6800,7 @@ int btrfs_map_block(struct btrfs_fs_info *fs_info, enum btrfs_map_op op, op != BTRFS_MAP_READ) { handle_ops_on_dev_replace(bioc, dev_replace, logical, &io_geom); } + up_read(&dev_replace->rwsem); *bioc_ret = bioc; bioc->num_stripes = io_geom.num_stripes; @@ -6796,11 +6808,6 @@ int btrfs_map_block(struct btrfs_fs_info *fs_info, enum btrfs_map_op op, bioc->mirror_num = io_geom.mirror_num; out: - if (dev_replace_is_ongoing) { - lockdep_assert_held(&dev_replace->rwsem); - /* Unlock and let waiting writers proceed */ - up_read(&dev_replace->rwsem); - } btrfs_free_chunk_map(map); return ret; }