| Message ID | 20240715130820.19907-1-jth@kernel.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v4] btrfs: don't hold dev_replace rwsem over whole of btrfs_map_block | expand |
On Mon, Jul 15, 2024 at 2:13 PM Johannes Thumshirn <jth@kernel.org> wrote: > > From: Johannes Thumshirn <johannes.thumshirn@wdc.com> > > 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. > > Signed-off-by: Johannes Thumshirn <johannes.thumshirn@wdc.com> > Reviewed-by: Josef Bacik <josef@toxicpanda.com> > Reviewed-by: Qu Wenruo <wqu@suse.com> > > --- > Cc: Filipe Manana <fdmanana@suse.com> > > Changes in v4: > - Free bioc in case we need to redo the mapping > Link to v3: > https://lore.kernel.org/linux-btrfs/20240712-b4-rst-updates-v3-1-5cf27dac98a7@kernel.org Reviewed-by: Filipe Manana <fdmanana@suse.com> Looks good now, thanks. > --- > 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 fcedc43ef291..9437e779d020 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; > } > -- > 2.43.0 > >
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index fcedc43ef291..9437e779d020 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; }