btrfs: using cached extent_state in set/unlock combinations

In several places the sequence (set_extent_uptodate, unlock_extent) is used.
This leads to a duplicate lookup of the extent state. This patch lets
set_extent_uptodate return a cached extent_state which can be passed to
unlock_extent_cached.
The occurences of the above sequences are updated to use the cache. Only
end_bio_extent_readpage is updated that it first gets a cached state to
pass it to the readpage_end_io_hook as the prototype requested and is later
on being used for set/unlock.

Signed-off-by: Arne Jansen <sensille@gmx.net>
Signed-off-by: Chris Mason <chris.mason@oracle.com>

3 files changed, 55 insertions, 19 deletions

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 864e0496cc1c..8dcfb77678de 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -690,6 +690,17 @@ static void cache_state(struct extent_state *state,
         }
 }
 
+static void uncache_state(struct extent_state **cached_ptr)
+{
+        if (cached_ptr && (*cached_ptr)) {
+                struct extent_state *state = *cached_ptr;
+                if (state->state & (EXTENT_IOBITS | EXTENT_BOUNDARY)) {
+                        *cached_ptr = NULL;
+                        free_extent_state(state);
+                }
+        }
+}
+
 /*
  * set some bits on a range in the tree.  This may require allocations or
  * sleeping, so the gfp mask is used to indicate what is allowed.
@@ -940,10 +951,10 @@ static int clear_extent_new(struct extent_io_tree *tree, u64 start, u64 end,
 }
 
 int set_extent_uptodate(struct extent_io_tree *tree, u64 start, u64 end,
-                        gfp_t mask)
+                        struct extent_state **cached_state, gfp_t mask)
 {
-        return set_extent_bit(tree, start, end, EXTENT_UPTODATE, 0, NULL,
-                              NULL, mask);
+        return set_extent_bit(tree, start, end, EXTENT_UPTODATE, 0,
+                              NULL, cached_state, mask);
 }
 
 static int clear_extent_uptodate(struct extent_io_tree *tree, u64 start,
@@ -1012,8 +1023,7 @@ int unlock_extent_cached(struct extent_io_tree *tree, u64 start, u64 end,
                                 mask);
 }
 
-int unlock_extent(struct extent_io_tree *tree, u64 start, u64 end,
-                  gfp_t mask)
+int unlock_extent(struct extent_io_tree *tree, u64 start, u64 end, gfp_t mask)
 {
         return clear_extent_bit(tree, start, end, EXTENT_LOCKED, 1, 0, NULL,
                                 mask);
@@ -1735,6 +1745,9 @@ static void end_bio_extent_readpage(struct bio *bio, int err)
 
         do {
                 struct page *page = bvec->bv_page;
+                struct extent_state *cached = NULL;
+                struct extent_state *state;
+
                 tree = &BTRFS_I(page->mapping->host)->io_tree;
 
                 start = ((u64)page->index << PAGE_CACHE_SHIFT) +
@@ -1749,9 +1762,20 @@ static void end_bio_extent_readpage(struct bio *bio, int err)
                 if (++bvec <= bvec_end)
                         prefetchw(&bvec->bv_page->flags);
 
+                spin_lock(&tree->lock);
+                state = find_first_extent_bit_state(tree, start, 0);
+                if (state) {
+                        /*
+                         * take a reference on the state, unlock will drop
+                         * the ref
+                         */
+                        cache_state(state, &cached);
+                }
+                spin_unlock(&tree->lock);
+
                 if (uptodate && tree->ops && tree->ops->readpage_end_io_hook) {
                         ret = tree->ops->readpage_end_io_hook(page, start, end,
-                                                              NULL);
+                                                              state);
                         if (ret)
                                 uptodate = 0;
                 }
@@ -1764,15 +1788,16 @@ static void end_bio_extent_readpage(struct bio *bio, int err)
                                         test_bit(BIO_UPTODATE, &bio->bi_flags);
                                 if (err)
                                         uptodate = 0;
+                                uncache_state(&cached);
                                 continue;
                         }
                 }
 
                 if (uptodate) {
-                        set_extent_uptodate(tree, start, end,
+                        set_extent_uptodate(tree, start, end, &cached,
                                             GFP_ATOMIC);
                 }
-                unlock_extent(tree, start, end, GFP_ATOMIC);
+                unlock_extent_cached(tree, start, end, &cached, GFP_ATOMIC);
 
                 if (whole_page) {
                         if (uptodate) {
@@ -1811,6 +1836,7 @@ static void end_bio_extent_preparewrite(struct bio *bio, int err)
 
         do {
                 struct page *page = bvec->bv_page;
+                struct extent_state *cached = NULL;
                 tree = &BTRFS_I(page->mapping->host)->io_tree;
 
                 start = ((u64)page->index << PAGE_CACHE_SHIFT) +
@@ -1821,13 +1847,14 @@ static void end_bio_extent_preparewrite(struct bio *bio, int err)
                         prefetchw(&bvec->bv_page->flags);
 
                 if (uptodate) {
-                        set_extent_uptodate(tree, start, end, GFP_ATOMIC);
+                        set_extent_uptodate(tree, start, end, &cached,
+                                            GFP_ATOMIC);
                 } else {
                         ClearPageUptodate(page);
                         SetPageError(page);
                 }
 
-                unlock_extent(tree, start, end, GFP_ATOMIC);
+                unlock_extent_cached(tree, start, end, &cached, GFP_ATOMIC);
 
         } while (bvec >= bio->bi_io_vec);
 
@@ -2016,14 +2043,17 @@ static int __extent_read_full_page(struct extent_io_tree *tree,
         while (cur <= end) {
                 if (cur >= last_byte) {
                         char *userpage;
+                        struct extent_state *cached = NULL;
+
                         iosize = PAGE_CACHE_SIZE - page_offset;
                         userpage = kmap_atomic(page, KM_USER0);
                         memset(userpage + page_offset, 0, iosize);
                         flush_dcache_page(page);
                         kunmap_atomic(userpage, KM_USER0);
                         set_extent_uptodate(tree, cur, cur + iosize - 1,
-                                            GFP_NOFS);
-                        unlock_extent(tree, cur, cur + iosize - 1, GFP_NOFS);
+                                            &cached, GFP_NOFS);
+                        unlock_extent_cached(tree, cur, cur + iosize - 1,
+                                             &cached, GFP_NOFS);
                         break;
                 }
                 em = get_extent(inode, page, page_offset, cur,
@@ -2063,14 +2093,17 @@ static int __extent_read_full_page(struct extent_io_tree *tree,
                 /* we've found a hole, just zero and go on */
                 if (block_start == EXTENT_MAP_HOLE) {
                         char *userpage;
+                        struct extent_state *cached = NULL;
+
                         userpage = kmap_atomic(page, KM_USER0);
                         memset(userpage + page_offset, 0, iosize);
                         flush_dcache_page(page);
                         kunmap_atomic(userpage, KM_USER0);
 
                         set_extent_uptodate(tree, cur, cur + iosize - 1,
-                                            GFP_NOFS);
-                        unlock_extent(tree, cur, cur + iosize - 1, GFP_NOFS);
+                                            &cached, GFP_NOFS);
+                        unlock_extent_cached(tree, cur, cur + iosize - 1,
+                                             &cached, GFP_NOFS);
                         cur = cur + iosize;
                         page_offset += iosize;
                         continue;
@@ -2789,9 +2822,12 @@ int extent_prepare_write(struct extent_io_tree *tree,
                         iocount++;
                         block_start = block_start + iosize;
                 } else {
-                        set_extent_uptodate(tree, block_start, cur_end,
+                        struct extent_state *cached = NULL;
+
+                        set_extent_uptodate(tree, block_start, cur_end, &cached,
                                             GFP_NOFS);
-                        unlock_extent(tree, block_start, cur_end, GFP_NOFS);
+                        unlock_extent_cached(tree, block_start, cur_end,
+                                             &cached, GFP_NOFS);
                         block_start = cur_end + 1;
                 }
                 page_offset = block_start & (PAGE_CACHE_SIZE - 1);
@@ -3457,7 +3493,7 @@ int set_extent_buffer_uptodate(struct extent_io_tree *tree,
         num_pages = num_extent_pages(eb->start, eb->len);
 
         set_extent_uptodate(tree, eb->start, eb->start + eb->len - 1,
-                            GFP_NOFS);
+                            NULL, GFP_NOFS);
         for (i = 0; i < num_pages; i++) {
                 page = extent_buffer_page(eb, i);
                 if ((i == 0 && (eb->start & (PAGE_CACHE_SIZE - 1))) ||
diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index f62c5442835d..af2d7179c372 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -208,7 +208,7 @@ int set_extent_bit(struct extent_io_tree *tree, u64 start, u64 end,
                    int bits, int exclusive_bits, u64 *failed_start,
                    struct extent_state **cached_state, gfp_t mask);
 int set_extent_uptodate(struct extent_io_tree *tree, u64 start, u64 end,
-                        gfp_t mask);
+                        struct extent_state **cached_state, gfp_t mask);
 int set_extent_new(struct extent_io_tree *tree, u64 start, u64 end,
                    gfp_t mask);
 int set_extent_dirty(struct extent_io_tree *tree, u64 start, u64 end,
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index edafc28883af..5a993e0ec865 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -5226,7 +5226,7 @@ again:
                         btrfs_mark_buffer_dirty(leaf);
                 }
                 set_extent_uptodate(io_tree, em->start,
-                                    extent_map_end(em) - 1, GFP_NOFS);
+                                    extent_map_end(em) - 1, NULL, GFP_NOFS);
                 goto insert;
         } else {
                 printk(KERN_ERR "btrfs unknown found_type %d\n", found_type);