diff options
Diffstat (limited to 'fs/btrfs/backref.c')
| -rw-r--r-- | fs/btrfs/backref.c | 85 |
1 files changed, 63 insertions, 22 deletions
diff --git a/fs/btrfs/backref.c b/fs/btrfs/backref.c index 90e40d5ceccd..e54f0884802a 100644 --- a/fs/btrfs/backref.c +++ b/fs/btrfs/backref.c @@ -1921,8 +1921,7 @@ int btrfs_is_data_extent_shared(struct btrfs_inode *inode, u64 bytenr, level = -1; ULIST_ITER_INIT(&uiter); while (1) { - bool is_shared; - bool cached; + const unsigned long prev_ref_count = ctx->refs.nnodes; walk_ctx.bytenr = bytenr; ret = find_parent_nodes(&walk_ctx, &shared); @@ -1940,21 +1939,36 @@ int btrfs_is_data_extent_shared(struct btrfs_inode *inode, u64 bytenr, ret = 0; /* - * If our data extent was not directly shared (without multiple - * reference items), than it might have a single reference item - * with a count > 1 for the same offset, which means there are 2 - * (or more) file extent items that point to the data extent - - * this happens when a file extent item needs to be split and - * then one item gets moved to another leaf due to a b+tree leaf - * split when inserting some item. In this case the file extent - * items may be located in different leaves and therefore some - * of the leaves may be referenced through shared subtrees while - * others are not. Since our extent buffer cache only works for - * a single path (by far the most common case and simpler to - * deal with), we can not use it if we have multiple leaves - * (which implies multiple paths). + * More than one extent buffer (bytenr) may have been added to + * the ctx->refs ulist, in which case we have to check multiple + * tree paths in case the first one is not shared, so we can not + * use the path cache which is made for a single path. Multiple + * extent buffers at the current level happen when: + * + * 1) level -1, the data extent: If our data extent was not + * directly shared (without multiple reference items), then + * it might have a single reference item with a count > 1 for + * the same offset, which means there are 2 (or more) file + * extent items that point to the data extent - this happens + * when a file extent item needs to be split and then one + * item gets moved to another leaf due to a b+tree leaf split + * when inserting some item. In this case the file extent + * items may be located in different leaves and therefore + * some of the leaves may be referenced through shared + * subtrees while others are not. Since our extent buffer + * cache only works for a single path (by far the most common + * case and simpler to deal with), we can not use it if we + * have multiple leaves (which implies multiple paths). + * + * 2) level >= 0, a tree node/leaf: We can have a mix of direct + * and indirect references on a b+tree node/leaf, so we have + * to check multiple paths, and the extent buffer (the + * current bytenr) may be shared or not. One example is + * during relocation as we may get a shared tree block ref + * (direct ref) and a non-shared tree block ref (indirect + * ref) for the same node/leaf. */ - if (level == -1 && ctx->refs.nnodes > 1) + if ((ctx->refs.nnodes - prev_ref_count) > 1) ctx->use_path_cache = false; if (level >= 0) @@ -1964,12 +1978,17 @@ int btrfs_is_data_extent_shared(struct btrfs_inode *inode, u64 bytenr, if (!node) break; bytenr = node->val; - level++; - cached = lookup_backref_shared_cache(ctx, root, bytenr, level, - &is_shared); - if (cached) { - ret = (is_shared ? 1 : 0); - break; + if (ctx->use_path_cache) { + bool is_shared; + bool cached; + + level++; + cached = lookup_backref_shared_cache(ctx, root, bytenr, + level, &is_shared); + if (cached) { + ret = (is_shared ? 1 : 0); + break; + } } shared.share_count = 0; shared.have_delayed_delete_refs = false; @@ -1977,6 +1996,28 @@ int btrfs_is_data_extent_shared(struct btrfs_inode *inode, u64 bytenr, } /* + * If the path cache is disabled, then it means at some tree level we + * got multiple parents due to a mix of direct and indirect backrefs or + * multiple leaves with file extent items pointing to the same data + * extent. We have to invalidate the cache and cache only the sharedness + * result for the levels where we got only one node/reference. + */ + if (!ctx->use_path_cache) { + int i = 0; + + level--; + if (ret >= 0 && level >= 0) { + bytenr = ctx->path_cache_entries[level].bytenr; + ctx->use_path_cache = true; + store_backref_shared_cache(ctx, root, bytenr, level, ret); + i = level + 1; + } + + for ( ; i < BTRFS_MAX_LEVEL; i++) + ctx->path_cache_entries[i].bytenr = 0; + } + + /* * Cache the sharedness result for the data extent if we know our inode * has more than 1 file extent item that refers to the data extent. */ |