From 815a51c74ad14864d0a8fff5eea983819c18feae Mon Sep 17 00:00:00 2001 From: Jan Schmidt Date: Wed, 16 May 2012 17:00:02 +0200 Subject: [PATCH] Btrfs: dummy extent buffers for tree mod log The tree modification log needs two ways to create dummy extent buffers, once by allocating a fresh one (to rebuild an old root) and once by cloning an existing one (to make private rewind modifications) to it. Signed-off-by: Jan Schmidt --- fs/btrfs/extent_io.c | 80 ++++++++++++++++++++++++++++++++++++++++---- fs/btrfs/extent_io.h | 3 ++ 2 files changed, 76 insertions(+), 7 deletions(-) diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index 2fb52c26c677..3daed70a401a 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -3930,6 +3930,7 @@ static struct extent_buffer *__alloc_extent_buffer(struct extent_io_tree *tree, eb->start = start; eb->len = len; eb->tree = tree; + eb->bflags = 0; rwlock_init(&eb->lock); atomic_set(&eb->write_locks, 0); atomic_set(&eb->read_locks, 0); @@ -3967,6 +3968,60 @@ static struct extent_buffer *__alloc_extent_buffer(struct extent_io_tree *tree, return eb; } +struct extent_buffer *btrfs_clone_extent_buffer(struct extent_buffer *src) +{ + unsigned long i; + struct page *p; + struct extent_buffer *new; + unsigned long num_pages = num_extent_pages(src->start, src->len); + + new = __alloc_extent_buffer(NULL, src->start, src->len, GFP_ATOMIC); + if (new == NULL) + return NULL; + + for (i = 0; i < num_pages; i++) { + p = alloc_page(GFP_ATOMIC); + BUG_ON(!p); + attach_extent_buffer_page(new, p); + WARN_ON(PageDirty(p)); + SetPageUptodate(p); + new->pages[i] = p; + } + + copy_extent_buffer(new, src, 0, 0, src->len); + set_bit(EXTENT_BUFFER_UPTODATE, &new->bflags); + set_bit(EXTENT_BUFFER_DUMMY, &new->bflags); + + return new; +} + +struct extent_buffer *alloc_dummy_extent_buffer(u64 start, unsigned long len) +{ + struct extent_buffer *eb; + unsigned long num_pages = num_extent_pages(0, len); + unsigned long i; + + eb = __alloc_extent_buffer(NULL, start, len, GFP_ATOMIC); + if (!eb) + return NULL; + + for (i = 0; i < num_pages; i++) { + eb->pages[i] = alloc_page(GFP_ATOMIC); + if (!eb->pages[i]) + goto err; + } + set_extent_buffer_uptodate(eb); + btrfs_set_header_nritems(eb, 0); + set_bit(EXTENT_BUFFER_DUMMY, &eb->bflags); + + return eb; +err: + for (i--; i > 0; i--) + __free_page(eb->pages[i]); + __free_extent_buffer(eb); + return NULL; +} + static int extent_buffer_under_io(struct extent_buffer *eb) { return (atomic_read(&eb->io_pages) || @@ -3982,6 +4037,7 @@ static void btrfs_release_extent_buffer_page(struct extent_buffer *eb, { unsigned long index; struct page *page; + int mapped = !test_bit(EXTENT_BUFFER_DUMMY, &eb->bflags); BUG_ON(extent_buffer_under_io(eb)); @@ -3992,7 +4048,7 @@ static void btrfs_release_extent_buffer_page(struct extent_buffer *eb, do { index--; page = extent_buffer_page(eb, index); - if (page) { + if (page && mapped) { spin_lock(&page->mapping->private_lock); /* * We do this since we'll remove the pages after we've @@ -4017,6 +4073,8 @@ static void btrfs_release_extent_buffer_page(struct extent_buffer *eb, } spin_unlock(&page->mapping->private_lock); + } + if (page) { /* One for when we alloced the page */ page_cache_release(page); } @@ -4235,14 +4293,18 @@ static void release_extent_buffer(struct extent_buffer *eb, gfp_t mask) { WARN_ON(atomic_read(&eb->refs) == 0); if (atomic_dec_and_test(&eb->refs)) { - struct extent_io_tree *tree = eb->tree; + if (test_bit(EXTENT_BUFFER_DUMMY, &eb->bflags)) { + spin_unlock(&eb->refs_lock); + } else { + struct extent_io_tree *tree = eb->tree; - spin_unlock(&eb->refs_lock); + spin_unlock(&eb->refs_lock); - spin_lock(&tree->buffer_lock); - radix_tree_delete(&tree->buffer, - eb->start >> PAGE_CACHE_SHIFT); - spin_unlock(&tree->buffer_lock); + spin_lock(&tree->buffer_lock); + radix_tree_delete(&tree->buffer, + eb->start >> PAGE_CACHE_SHIFT); + spin_unlock(&tree->buffer_lock); + } /* Should be safe to release our pages at this point */ btrfs_release_extent_buffer_page(eb, 0); @@ -4259,6 +4321,10 @@ void free_extent_buffer(struct extent_buffer *eb) return; spin_lock(&eb->refs_lock); + if (atomic_read(&eb->refs) == 2 && + test_bit(EXTENT_BUFFER_DUMMY, &eb->bflags)) + atomic_dec(&eb->refs); + if (atomic_read(&eb->refs) == 2 && test_bit(EXTENT_BUFFER_STALE, &eb->bflags) && !extent_buffer_under_io(eb) && diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h index b516c3b8dec6..96434a61d7c2 100644 --- a/fs/btrfs/extent_io.h +++ b/fs/btrfs/extent_io.h @@ -39,6 +39,7 @@ #define EXTENT_BUFFER_STALE 6 #define EXTENT_BUFFER_WRITEBACK 7 #define EXTENT_BUFFER_IOERR 8 +#define EXTENT_BUFFER_DUMMY 9 /* these are flags for extent_clear_unlock_delalloc */ #define EXTENT_CLEAR_UNLOCK_PAGE 0x1 @@ -265,6 +266,8 @@ void set_page_extent_mapped(struct page *page); struct extent_buffer *alloc_extent_buffer(struct extent_io_tree *tree, u64 start, unsigned long len); +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); void free_extent_buffer(struct extent_buffer *eb); -- GitLab