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Commit 815a51c7 authored by Jan Schmidt's avatar Jan Schmidt
Browse files

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: default avatarJan Schmidt <list.btrfs@jan-o-sch.net>
parent 64947ec0

fs/btrfs/extent_io.c

+73 −7
Original line number Diff line number Diff line
@@ -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);

		}
@@ -4235,6 +4293,9 @@ 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)) {

		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);
@@ -4243,6 +4304,7 @@ static void release_extent_buffer(struct extent_buffer *eb, gfp_t mask) 
			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) &&

fs/btrfs/extent_io.h

+3 −0
Original line number Diff line number Diff line
@@ -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);