From: Matthew Wilcox <mawil...@microsoft.com> Eliminate the buffer_lock as the internal xa_lock provides all the necessary protection. We can remove the radix_tree_preload calls, but I can't find a good way to use the 'exists' result from xa_cmpxchg(). We could resort to the advanced API to improve this, but it's a really unlikely case (nothing in the xarray when we first look; something there when we try to add the newly-allocated extent buffer), so I think it's not worth optimising for.
Signed-off-by: Matthew Wilcox <mawil...@microsoft.com> --- fs/btrfs/ctree.h | 5 ++- fs/btrfs/disk-io.c | 3 +- fs/btrfs/extent_io.c | 82 ++++++++++++++++++-------------------------- fs/btrfs/tests/btrfs-tests.c | 26 +++----------- 4 files changed, 40 insertions(+), 76 deletions(-) diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h index 272d099bed7e..87984ce3a4c2 100644 --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -1058,9 +1058,8 @@ struct btrfs_fs_info { /* readahead works cnt */ atomic_t reada_works_cnt; - /* Extent buffer radix tree */ - spinlock_t buffer_lock; - struct radix_tree_root buffer_radix; + /* Extent buffer array */ + struct xarray buffer_array; /* next backup root to be overwritten */ int backup_root_index; diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index 1eae29045d43..650d1350b64d 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -2429,7 +2429,7 @@ int open_ctree(struct super_block *sb, } xa_init(&fs_info->fs_roots); - INIT_RADIX_TREE(&fs_info->buffer_radix, GFP_ATOMIC); + xa_init(&fs_info->buffer_array); INIT_LIST_HEAD(&fs_info->trans_list); INIT_LIST_HEAD(&fs_info->dead_roots); INIT_LIST_HEAD(&fs_info->delayed_iputs); @@ -2442,7 +2442,6 @@ int open_ctree(struct super_block *sb, spin_lock_init(&fs_info->tree_mod_seq_lock); spin_lock_init(&fs_info->super_lock); spin_lock_init(&fs_info->qgroup_op_lock); - spin_lock_init(&fs_info->buffer_lock); spin_lock_init(&fs_info->unused_bgs_lock); rwlock_init(&fs_info->tree_mod_log_lock); mutex_init(&fs_info->unused_bg_unpin_mutex); diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index fd5e9d887328..2b43fa11c9e2 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -4884,8 +4884,7 @@ struct extent_buffer *find_extent_buffer(struct btrfs_fs_info *fs_info, struct extent_buffer *eb; rcu_read_lock(); - eb = radix_tree_lookup(&fs_info->buffer_radix, - start >> PAGE_SHIFT); + eb = xa_load(&fs_info->buffer_array, start >> PAGE_SHIFT); if (eb && atomic_inc_not_zero(&eb->refs)) { rcu_read_unlock(); /* @@ -4919,31 +4918,24 @@ struct extent_buffer *find_extent_buffer(struct btrfs_fs_info *fs_info, struct extent_buffer *alloc_test_extent_buffer(struct btrfs_fs_info *fs_info, u64 start) { - struct extent_buffer *eb, *exists = NULL; - int ret; + struct extent_buffer *exists, *eb = NULL; - eb = find_extent_buffer(fs_info, start); - if (eb) - return eb; - eb = alloc_dummy_extent_buffer(fs_info, start); - if (!eb) - return NULL; - eb->fs_info = fs_info; again: - ret = radix_tree_preload(GFP_NOFS); - if (ret) + exists = find_extent_buffer(fs_info, start); + if (exists) goto free_eb; - spin_lock(&fs_info->buffer_lock); - ret = radix_tree_insert(&fs_info->buffer_radix, - start >> PAGE_SHIFT, eb); - spin_unlock(&fs_info->buffer_lock); - radix_tree_preload_end(); - if (ret == -EEXIST) { - exists = find_extent_buffer(fs_info, start); - if (exists) + if (!eb) + eb = alloc_dummy_extent_buffer(fs_info, start); + if (!eb) + return NULL; + exists = xa_cmpxchg(&fs_info->buffer_array, start >> PAGE_SHIFT, + NULL, eb, GFP_NOFS); + if (unlikely(exists)) { + if (xa_is_err(exists)) { + exists = NULL; goto free_eb; - else - goto again; + } + goto again; } check_buffer_tree_ref(eb); set_bit(EXTENT_BUFFER_IN_TREE, &eb->bflags); @@ -4957,7 +4949,8 @@ struct extent_buffer *alloc_test_extent_buffer(struct btrfs_fs_info *fs_info, atomic_inc(&eb->refs); return eb; free_eb: - btrfs_release_extent_buffer(eb); + if (eb) + btrfs_release_extent_buffer(eb); return exists; } #endif @@ -4969,22 +4962,24 @@ struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info, unsigned long num_pages = num_extent_pages(start, len); unsigned long i; unsigned long index = start >> PAGE_SHIFT; - struct extent_buffer *eb; + struct extent_buffer *eb = NULL; struct extent_buffer *exists = NULL; struct page *p; struct address_space *mapping = fs_info->btree_inode->i_mapping; int uptodate = 1; - int ret; if (!IS_ALIGNED(start, fs_info->sectorsize)) { btrfs_err(fs_info, "bad tree block start %llu", start); return ERR_PTR(-EINVAL); } - eb = find_extent_buffer(fs_info, start); - if (eb) - return eb; +again: + exists = find_extent_buffer(fs_info, start); + if (exists) + goto free_eb; + if (eb) + goto add; eb = __alloc_extent_buffer(fs_info, start, len); if (!eb) return ERR_PTR(-ENOMEM); @@ -5037,24 +5032,15 @@ struct extent_buffer *alloc_extent_buffer(struct btrfs_fs_info *fs_info, } if (uptodate) set_bit(EXTENT_BUFFER_UPTODATE, &eb->bflags); -again: - ret = radix_tree_preload(GFP_NOFS); - if (ret) { - exists = ERR_PTR(ret); - goto free_eb; - } - - spin_lock(&fs_info->buffer_lock); - ret = radix_tree_insert(&fs_info->buffer_radix, - start >> PAGE_SHIFT, eb); - spin_unlock(&fs_info->buffer_lock); - radix_tree_preload_end(); - if (ret == -EEXIST) { - exists = find_extent_buffer(fs_info, start); - if (exists) +add: + exists = xa_cmpxchg(&fs_info->buffer_array, start >> PAGE_SHIFT, + NULL, eb, GFP_NOFS); + if (unlikely(exists)) { + if (xa_is_err(exists)) { + exists = NULL; goto free_eb; - else - goto again; + } + goto again; } /* add one reference for the tree */ check_buffer_tree_ref(eb); @@ -5107,10 +5093,8 @@ static int release_extent_buffer(struct extent_buffer *eb) spin_unlock(&eb->refs_lock); - spin_lock(&fs_info->buffer_lock); - radix_tree_delete(&fs_info->buffer_radix, + xa_erase(&fs_info->buffer_array, eb->start >> PAGE_SHIFT); - spin_unlock(&fs_info->buffer_lock); } else { spin_unlock(&eb->refs_lock); } diff --git a/fs/btrfs/tests/btrfs-tests.c b/fs/btrfs/tests/btrfs-tests.c index 570bce31a301..f80fd54903e9 100644 --- a/fs/btrfs/tests/btrfs-tests.c +++ b/fs/btrfs/tests/btrfs-tests.c @@ -110,7 +110,6 @@ struct btrfs_fs_info *btrfs_alloc_dummy_fs_info(u32 nodesize, u32 sectorsize) return NULL; } - spin_lock_init(&fs_info->buffer_lock); spin_lock_init(&fs_info->qgroup_lock); spin_lock_init(&fs_info->qgroup_op_lock); spin_lock_init(&fs_info->super_lock); @@ -125,7 +124,7 @@ struct btrfs_fs_info *btrfs_alloc_dummy_fs_info(u32 nodesize, u32 sectorsize) INIT_LIST_HEAD(&fs_info->dirty_qgroups); INIT_LIST_HEAD(&fs_info->dead_roots); INIT_LIST_HEAD(&fs_info->tree_mod_seq_list); - INIT_RADIX_TREE(&fs_info->buffer_radix, GFP_ATOMIC); + xa_init(&fs_info->buffer_array); xa_init(&fs_info->fs_roots); extent_io_tree_init(&fs_info->freed_extents[0], NULL); extent_io_tree_init(&fs_info->freed_extents[1], NULL); @@ -139,8 +138,8 @@ struct btrfs_fs_info *btrfs_alloc_dummy_fs_info(u32 nodesize, u32 sectorsize) void btrfs_free_dummy_fs_info(struct btrfs_fs_info *fs_info) { - struct radix_tree_iter iter; - void **slot; + struct extent_buffer *eb; + unsigned long index = 0; if (!fs_info) return; @@ -151,25 +150,8 @@ void btrfs_free_dummy_fs_info(struct btrfs_fs_info *fs_info) test_mnt->mnt_sb->s_fs_info = NULL; - spin_lock(&fs_info->buffer_lock); - radix_tree_for_each_slot(slot, &fs_info->buffer_radix, &iter, 0) { - struct extent_buffer *eb; - - eb = radix_tree_deref_slot_protected(slot, &fs_info->buffer_lock); - if (!eb) - continue; - /* Shouldn't happen but that kind of thinking creates CVE's */ - if (radix_tree_exception(eb)) { - if (radix_tree_deref_retry(eb)) - slot = radix_tree_iter_retry(&iter); - continue; - } - slot = radix_tree_iter_resume(slot, &iter); - spin_unlock(&fs_info->buffer_lock); + xa_for_each(&fs_info->buffer_array, eb, index, ULONG_MAX, XA_PRESENT) free_extent_buffer_stale(eb); - spin_lock(&fs_info->buffer_lock); - } - spin_unlock(&fs_info->buffer_lock); btrfs_free_qgroup_config(fs_info); btrfs_free_fs_roots(fs_info); -- 2.15.1 _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu