On 03/09/2012 02:37 AM, Josef Bacik wrote:
> We spend a lot of time looking up extent buffers from pages when we could just
> store the pointer to the eb the page is associated with in page->private.
> This
> patch does just that, and it makes things a little simpler and reduces a bit
> of
> CPU overhead involved with doing metadata IO. Thanks,
>
Hi Josef,
This is not against the normal branch, so we must inform people that. :)
Have a quick look, and I guess it is for "Btrfs: allow metadata blocks larger
than the page size", isn't it?
thanks,
liubo
> Signed-off-by: Josef Bacik <jo...@redhat.com>
> ---
> fs/btrfs/disk-io.c | 92 ++++++++++++-------------------------------------
> fs/btrfs/extent_io.c | 92 ++++++++++++++++++++++++++++++++++++-------------
> fs/btrfs/extent_io.h | 1 +
> 3 files changed, 91 insertions(+), 94 deletions(-)
>
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index 33114bc..6f97129 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -403,39 +403,28 @@ static int csum_dirty_buffer(struct btrfs_root *root,
> struct page *page)
> struct extent_io_tree *tree;
> u64 start = (u64)page->index << PAGE_CACHE_SHIFT;
> u64 found_start;
> - unsigned long len;
> struct extent_buffer *eb;
>
> tree = &BTRFS_I(page->mapping->host)->io_tree;
>
> - if (page->private == EXTENT_PAGE_PRIVATE)
> - goto out;
> - if (!page->private) {
> - WARN_ON(1);
> - goto out;
> - }
> - len = page->private >> 2;
> - WARN_ON(len == 0);
> -
> - eb = find_extent_buffer(tree, start, len);
> + eb = (struct extent_buffer *)page->private;
> + if (page != eb->pages[0])
> + return 0;
>
> found_start = btrfs_header_bytenr(eb);
> if (found_start != start) {
> WARN_ON(1);
> - goto err;
> + return 0;
> }
> if (eb->pages[0] != page) {
> WARN_ON(1);
> - goto err;
> + return 0;
> }
> if (!PageUptodate(page)) {
> WARN_ON(1);
> - goto err;
> + return 0;
> }
> csum_tree_block(root, eb, 0);
> -err:
> - free_extent_buffer(eb);
> -out:
> return 0;
> }
>
> @@ -566,7 +555,6 @@ static int btree_readpage_end_io_hook(struct page *page,
> u64 start, u64 end,
> struct extent_io_tree *tree;
> u64 found_start;
> int found_level;
> - unsigned long len;
> struct extent_buffer *eb;
> struct btrfs_root *root = BTRFS_I(page->mapping->host)->root;
> int ret = 0;
> @@ -576,13 +564,8 @@ static int btree_readpage_end_io_hook(struct page *page,
> u64 start, u64 end,
> goto out;
>
> tree = &BTRFS_I(page->mapping->host)->io_tree;
> - len = page->private >> 2;
> + eb = (struct extent_buffer *)page->private;
>
> - eb = find_eb_for_page(tree, page, max(root->leafsize, root->nodesize));
> - if (!eb) {
> - ret = -EIO;
> - goto out;
> - }
> reads_done = atomic_dec_and_test(&eb->pages_reading);
> if (!reads_done)
> goto err;
> @@ -631,7 +614,6 @@ err:
>
> if (ret && eb)
> clear_extent_buffer_uptodate(tree, eb, NULL);
> - free_extent_buffer(eb);
> out:
> return ret;
> }
> @@ -640,31 +622,17 @@ static int btree_io_failed_hook(struct bio *failed_bio,
> struct page *page, u64 start, u64 end,
> int mirror_num, struct extent_state *state)
> {
> - struct extent_io_tree *tree;
> - unsigned long len;
> struct extent_buffer *eb;
> struct btrfs_root *root = BTRFS_I(page->mapping->host)->root;
>
> - tree = &BTRFS_I(page->mapping->host)->io_tree;
> - if (page->private == EXTENT_PAGE_PRIVATE)
> - goto out;
> - if (!page->private)
> - goto out;
> -
> - len = page->private >> 2;
> - WARN_ON(len == 0);
> -
> - eb = alloc_extent_buffer(tree, start, len);
> - if (eb == NULL)
> - goto out;
> + eb = (struct extent_buffer *)page->private;
> + if (page != eb->pages[0])
> + return -EIO;
>
> if (test_bit(EXTENT_BUFFER_READAHEAD, &eb->bflags)) {
> clear_bit(EXTENT_BUFFER_READAHEAD, &eb->bflags);
> btree_readahead_hook(root, eb, eb->start, -EIO);
> }
> - free_extent_buffer(eb);
> -
> -out:
> return -EIO; /* we fixed nothing */
> }
>
> @@ -955,10 +923,8 @@ static int btree_readpage(struct file *file, struct page
> *page)
>
> static int btree_releasepage(struct page *page, gfp_t gfp_flags)
> {
> - struct extent_io_tree *tree;
> struct extent_map_tree *map;
> - struct extent_buffer *eb;
> - struct btrfs_root *root;
> + struct extent_io_tree *tree;
> int ret;
>
> if (PageWriteback(page) || PageDirty(page))
> @@ -967,26 +933,11 @@ static int btree_releasepage(struct page *page, gfp_t
> gfp_flags)
> tree = &BTRFS_I(page->mapping->host)->io_tree;
> map = &BTRFS_I(page->mapping->host)->extent_tree;
>
> - root = BTRFS_I(page->mapping->host)->root;
> - if (page->private == EXTENT_PAGE_PRIVATE) {
> - eb = find_eb_for_page(tree, page, max(root->leafsize,
> root->nodesize));
> - free_extent_buffer(eb);
> - if (eb)
> - return 0;
> - }
> -
> ret = try_release_extent_state(map, tree, page, gfp_flags);
> if (!ret)
> return 0;
>
> - ret = try_release_extent_buffer(tree, page);
> - if (ret == 1) {
> - ClearPagePrivate(page);
> - set_page_private(page, 0);
> - page_cache_release(page);
> - }
> -
> - return ret;
> + return try_release_extent_buffer(tree, page);
> }
>
> static void btree_invalidatepage(struct page *page, unsigned long offset)
> @@ -3173,17 +3124,21 @@ static int btree_lock_page_hook(struct page *page,
> void *data,
> {
> struct inode *inode = page->mapping->host;
> struct btrfs_root *root = BTRFS_I(inode)->root;
> - struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
> struct extent_buffer *eb;
> - unsigned long len;
> - u64 bytenr = page_offset(page);
>
> - if (page->private == EXTENT_PAGE_PRIVATE)
> + /*
> + * We culled this eb but the page is still hanging out on the mapping,
> + * carry on.
> + */
> + if (!PagePrivate(page))
> goto out;
>
> - len = page->private >> 2;
> - eb = find_extent_buffer(io_tree, bytenr, len);
> - if (!eb)
> + eb = (struct extent_buffer *)page->private;
> + if (!eb) {
> + WARN_ON(1);
> + goto out;
> + }
> + if (page != eb->pages[0])
> goto out;
>
> if (!btrfs_try_tree_write_lock(eb)) {
> @@ -3202,7 +3157,6 @@ static int btree_lock_page_hook(struct page *page, void
> *data,
> }
>
> btrfs_tree_unlock(eb);
> - free_extent_buffer(eb);
> out:
> if (!trylock_page(page)) {
> flush_fn(data);
> diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
> index d4795fc..197595a 100644
> --- a/fs/btrfs/extent_io.c
> +++ b/fs/btrfs/extent_io.c
> @@ -2462,19 +2462,24 @@ static int submit_extent_page(int rw, struct
> extent_io_tree *tree,
> return ret;
> }
>
> -void set_page_extent_mapped(struct page *page)
> +void attach_extent_buffer_page(struct extent_buffer *eb, struct page *page)
> {
> if (!PagePrivate(page)) {
> SetPagePrivate(page);
> page_cache_get(page);
> - set_page_private(page, EXTENT_PAGE_PRIVATE);
> + set_page_private(page, (unsigned long)eb);
> + } else {
> + WARN_ON(page->private != (unsigned long)eb);
> }
> }
>
> -static void set_page_extent_head(struct page *page, unsigned long len)
> +void set_page_extent_mapped(struct page *page)
> {
> - WARN_ON(!PagePrivate(page));
> - set_page_private(page, EXTENT_PAGE_PRIVATE_FIRST_PAGE | len << 2);
> + if (!PagePrivate(page)) {
> + SetPagePrivate(page);
> + page_cache_get(page);
> + set_page_private(page, EXTENT_PAGE_PRIVATE);
> + }
> }
>
> /*
> @@ -3567,6 +3572,7 @@ static struct extent_buffer
> *__alloc_extent_buffer(struct extent_io_tree *tree,
> return NULL;
> eb->start = start;
> eb->len = len;
> + eb->tree = tree;
> rwlock_init(&eb->lock);
> atomic_set(&eb->write_locks, 0);
> atomic_set(&eb->read_locks, 0);
> @@ -3619,8 +3625,31 @@ static void btrfs_release_extent_buffer_page(struct
> extent_buffer *eb,
> do {
> index--;
> page = extent_buffer_page(eb, index);
> - if (page)
> + if (page) {
> + spin_lock(&page->mapping->private_lock);
> + /*
> + * We do this since we'll remove the pages after we've
> + * removed the eb from the radix tree, so we could race
> + * and have this page now attached to the new eb. So
> + * only clear page_private if it's still connected to
> + * this eb.
> + */
> + if (PagePrivate(page) &&
> + page->private == (unsigned long)eb) {
> + /*
> + * We need to make sure we haven't be attached
> + * to a new eb.
> + */
> + ClearPagePrivate(page);
> + set_page_private(page, 0);
> + /* One for the page private */
> + page_cache_release(page);
> + }
> + spin_unlock(&page->mapping->private_lock);
> +
> + /* One for when we alloced the page */
> page_cache_release(page);
> + }
> } while (index != start_idx);
> }
>
> @@ -3665,6 +3694,32 @@ struct extent_buffer *alloc_extent_buffer(struct
> extent_io_tree *tree,
> WARN_ON(1);
> goto free_eb;
> }
> +
> + spin_lock(&mapping->private_lock);
> + if (PagePrivate(p)) {
> + /*
> + * We could have already allocated an eb for this page
> + * and attached one so lets see if we can get a ref on
> + * the existing eb, and if we can we know it's good and
> + * we can just return that one, else we know we can just
> + * overwrite page->private.
> + */
> + exists = (struct extent_buffer *)p->private;
> + if (atomic_inc_not_zero(&exists->refs)) {
> + spin_unlock(&mapping->private_lock);
> + unlock_page(p);
> + goto free_eb;
> + }
> +
> + /*
> + * Do this so attach doesn't complain and we need to
> + * drop the ref the old guy had.
> + */
> + ClearPagePrivate(p);
> + page_cache_release(p);
> + }
> + attach_extent_buffer_page(eb, p);
> + spin_unlock(&mapping->private_lock);
> mark_page_accessed(p);
> eb->pages[i] = p;
> if (!PageUptodate(p))
> @@ -3687,7 +3742,6 @@ struct extent_buffer *alloc_extent_buffer(struct
> extent_io_tree *tree,
> if (ret == -EEXIST) {
> exists = radix_tree_lookup(&tree->buffer,
> start >> PAGE_CACHE_SHIFT);
> - /* add one reference for the caller */
> atomic_inc(&exists->refs);
> spin_unlock(&tree->buffer_lock);
> radix_tree_preload_end();
> @@ -3707,12 +3761,9 @@ struct extent_buffer *alloc_extent_buffer(struct
> extent_io_tree *tree,
> * after the extent buffer is in the radix tree so
> * it doesn't get lost
> */
> - set_page_extent_mapped(eb->pages[0]);
> - set_page_extent_head(eb->pages[0], eb->len);
> SetPageChecked(eb->pages[0]);
> for (i = 1; i < num_pages; i++) {
> p = extent_buffer_page(eb, i);
> - set_page_extent_mapped(p);
> ClearPageChecked(p);
> unlock_page(p);
> }
> @@ -3776,10 +3827,6 @@ int clear_extent_buffer_dirty(struct extent_io_tree
> *tree,
> lock_page(page);
> WARN_ON(!PagePrivate(page));
>
> - set_page_extent_mapped(page);
> - if (i == 0)
> - set_page_extent_head(page, eb->len);
> -
> clear_page_dirty_for_io(page);
> spin_lock_irq(&page->mapping->tree_lock);
> if (!PageDirty(page)) {
> @@ -3991,9 +4038,6 @@ int read_extent_buffer_pages(struct extent_io_tree
> *tree,
> atomic_set(&eb->pages_reading, num_reads);
> for (i = start_i; i < num_pages; i++) {
> page = extent_buffer_page(eb, i);
> - set_page_extent_mapped(page);
> - if (i == 0)
> - set_page_extent_head(page, eb->len);
> if (!PageUptodate(page)) {
> ClearPageError(page);
> err = __extent_read_full_page(tree, page,
> @@ -4376,22 +4420,19 @@ static inline void
> btrfs_release_extent_buffer_rcu(struct rcu_head *head)
> struct extent_buffer *eb =
> container_of(head, struct extent_buffer, rcu_head);
>
> - btrfs_release_extent_buffer(eb);
> + __free_extent_buffer(eb);
> }
>
> int try_release_extent_buffer(struct extent_io_tree *tree, struct page *page)
> {
> u64 start = page_offset(page);
> - struct extent_buffer *eb;
> + struct extent_buffer *eb = (struct extent_buffer *)page->private;
> int ret = 1;
>
> - spin_lock(&tree->buffer_lock);
> - eb = radix_tree_lookup(&tree->buffer, start >> PAGE_CACHE_SHIFT);
> - if (!eb) {
> - spin_unlock(&tree->buffer_lock);
> - return ret;
> - }
> + if (!PagePrivate(page) || !eb)
> + return 1;
>
> + spin_lock(&tree->buffer_lock);
> if (atomic_read(&eb->refs) > 1 ||
> test_bit(EXTENT_BUFFER_DIRTY, &eb->bflags)) {
> ret = 0;
> @@ -4407,6 +4448,7 @@ int try_release_extent_buffer(struct extent_io_tree
> *tree, struct page *page)
> goto out;
> }
> radix_tree_delete(&tree->buffer, start >> PAGE_CACHE_SHIFT);
> + btrfs_release_extent_buffer_page(eb, 0);
> out:
> spin_unlock(&tree->buffer_lock);
>
> diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
> index 9b6c8f3..f030a2d 100644
> --- a/fs/btrfs/extent_io.h
> +++ b/fs/btrfs/extent_io.h
> @@ -127,6 +127,7 @@ struct extent_buffer {
> unsigned long map_start;
> unsigned long map_len;
> unsigned long bflags;
> + struct extent_io_tree *tree;
> atomic_t refs;
> atomic_t pages_reading;
> struct list_head leak_list;
--
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