From 452c75c3d2187089f6e846710e6ea7883bf30f8a Mon Sep 17 00:00:00 2001 From: Chandra Seetharaman Date: Mon, 7 Oct 2013 10:45:25 -0500 Subject: [PATCH] Btrfs: Simplify the logic in alloc_extent_buffer() for existing extent buffer case alloc_extent_buffer() uses radix_tree_lookup() when radix_tree_insert() fails with EEXIST. That part of the code is very similar to the code in find_extent_buffer(). This patch replaces radix_tree_lookup() and surrounding code in alloc_extent_buffer() with find_extent_buffer(). Note that radix_tree_lookup() does not need to be protected by tree->buffer_lock. It is protected by eb->refs. While at it, this patch - changes the other usage of radix_tree_lookup() in alloc_extent_buffer() with find_extent_buffer() to reduce redundancy. - removes the unused argument 'len' to find_extent_buffer(). Signed-Off-by: Chandra Seetharaman Reviewed-by: Zach Brown Signed-off-by: Josef Bacik Signed-off-by: Chris Mason --- fs/btrfs/disk-io.c | 3 +-- fs/btrfs/extent_io.c | 63 ++++++++++++++++++-------------------------- fs/btrfs/extent_io.h | 2 +- 3 files changed, 28 insertions(+), 40 deletions(-) diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index b0ea9f4bbc70..ebc784aba3f5 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -1104,8 +1104,7 @@ struct extent_buffer *btrfs_find_tree_block(struct btrfs_root *root, { struct inode *btree_inode = root->fs_info->btree_inode; struct extent_buffer *eb; - eb = find_extent_buffer(&BTRFS_I(btree_inode)->io_tree, - bytenr, blocksize); + eb = find_extent_buffer(&BTRFS_I(btree_inode)->io_tree, bytenr); return eb; } diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index c10291cc4fd1..5439f24ab06b 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -4486,6 +4486,23 @@ static void mark_extent_buffer_accessed(struct extent_buffer *eb) } } +struct extent_buffer *find_extent_buffer(struct extent_io_tree *tree, + u64 start) +{ + struct extent_buffer *eb; + + rcu_read_lock(); + eb = radix_tree_lookup(&tree->buffer, start >> PAGE_CACHE_SHIFT); + if (eb && atomic_inc_not_zero(&eb->refs)) { + rcu_read_unlock(); + mark_extent_buffer_accessed(eb); + return eb; + } + rcu_read_unlock(); + + return NULL; +} + struct extent_buffer *alloc_extent_buffer(struct extent_io_tree *tree, u64 start, unsigned long len) { @@ -4499,14 +4516,10 @@ struct extent_buffer *alloc_extent_buffer(struct extent_io_tree *tree, int uptodate = 1; int ret; - rcu_read_lock(); - eb = radix_tree_lookup(&tree->buffer, start >> PAGE_CACHE_SHIFT); - if (eb && atomic_inc_not_zero(&eb->refs)) { - rcu_read_unlock(); - mark_extent_buffer_accessed(eb); + + eb = find_extent_buffer(tree, start); + if (eb) return eb; - } - rcu_read_unlock(); eb = __alloc_extent_buffer(tree, start, len, GFP_NOFS); if (!eb) @@ -4565,24 +4578,17 @@ again: spin_lock(&tree->buffer_lock); ret = radix_tree_insert(&tree->buffer, start >> PAGE_CACHE_SHIFT, eb); + spin_unlock(&tree->buffer_lock); + radix_tree_preload_end(); if (ret == -EEXIST) { - exists = radix_tree_lookup(&tree->buffer, - start >> PAGE_CACHE_SHIFT); - if (!atomic_inc_not_zero(&exists->refs)) { - spin_unlock(&tree->buffer_lock); - radix_tree_preload_end(); - exists = NULL; + exists = find_extent_buffer(tree, start); + if (exists) + goto free_eb; + else goto again; - } - spin_unlock(&tree->buffer_lock); - radix_tree_preload_end(); - mark_extent_buffer_accessed(exists); - goto free_eb; } /* add one reference for the tree */ check_buffer_tree_ref(eb); - spin_unlock(&tree->buffer_lock); - radix_tree_preload_end(); /* * there is a race where release page may have @@ -4613,23 +4619,6 @@ free_eb: return exists; } -struct extent_buffer *find_extent_buffer(struct extent_io_tree *tree, - u64 start, unsigned long len) -{ - struct extent_buffer *eb; - - rcu_read_lock(); - eb = radix_tree_lookup(&tree->buffer, start >> PAGE_CACHE_SHIFT); - if (eb && atomic_inc_not_zero(&eb->refs)) { - rcu_read_unlock(); - mark_extent_buffer_accessed(eb); - return eb; - } - rcu_read_unlock(); - - return NULL; -} - static inline void btrfs_release_extent_buffer_rcu(struct rcu_head *head) { struct extent_buffer *eb = diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h index f98602eac808..19620c58f096 100644 --- a/fs/btrfs/extent_io.h +++ b/fs/btrfs/extent_io.h @@ -271,7 +271,7 @@ struct extent_buffer *alloc_extent_buffer(struct extent_io_tree *tree, struct extent_buffer *alloc_dummy_extent_buffer(u64 start, unsigned long len); struct extent_buffer *btrfs_clone_extent_buffer(struct extent_buffer *src); struct extent_buffer *find_extent_buffer(struct extent_io_tree *tree, - u64 start, unsigned long len); + u64 start); void free_extent_buffer(struct extent_buffer *eb); void free_extent_buffer_stale(struct extent_buffer *eb); #define WAIT_NONE 0