Btrfs: Avoid memcpy where possible in extent_buffers

Signed-off-by: Chris Mason <chris.mason@oracle.com>

1 files changed, 102 insertions, 30 deletions

diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
index 8bef309e1b37..d2c733c68b4c 100644
--- a/fs/btrfs/extent_map.c
+++ b/fs/btrfs/extent_map.c
@@ -18,6 +18,11 @@ struct kmem_cache *btrfs_cache_create(const char *name, size_t size,
 
 static struct kmem_cache *extent_map_cache;
 static struct kmem_cache *extent_state_cache;
+static struct kmem_cache *extent_buffer_cache;
+static LIST_HEAD(extent_buffers);
+static spinlock_t extent_buffers_lock;
+static int nr_extent_buffers;
+#define MAX_EXTENT_BUFFER_CACHE 128
 
 struct tree_entry {
         u64 start;
@@ -29,21 +34,33 @@ struct tree_entry {
 void __init extent_map_init(void)
 {
         extent_map_cache = btrfs_cache_create("extent_map",
-                                            sizeof(struct extent_map),
-                                            SLAB_DESTROY_BY_RCU,
+                                            sizeof(struct extent_map), 0,
                                             NULL);
         extent_state_cache = btrfs_cache_create("extent_state",
-                                            sizeof(struct extent_state),
-                                            SLAB_DESTROY_BY_RCU,
+                                            sizeof(struct extent_state), 0,
                                             NULL);
+        extent_buffer_cache = btrfs_cache_create("extent_buffers",
+                                            sizeof(struct extent_buffer), 0,
+                                            NULL);
+        spin_lock_init(&extent_buffers_lock);
 }
 
 void __exit extent_map_exit(void)
 {
+        struct extent_buffer *eb;
+
+        while (!list_empty(&extent_buffers)) {
+                eb = list_entry(extent_buffers.next,
+                                struct extent_buffer, list);
+                list_del(&eb->list);
+                kmem_cache_free(extent_buffer_cache, eb);
+        }
         if (extent_map_cache)
                 kmem_cache_destroy(extent_map_cache);
         if (extent_state_cache)
                 kmem_cache_destroy(extent_state_cache);
+        if (extent_buffer_cache)
+                kmem_cache_destroy(extent_buffer_cache);
 }
 
 void extent_map_tree_init(struct extent_map_tree *tree,
@@ -1858,6 +1875,48 @@ sector_t extent_bmap(struct address_space *mapping, sector_t iblock,
         return (em->block_start + start - em->start) >> inode->i_blkbits;
 }
 
+static struct extent_buffer *__alloc_extent_buffer(gfp_t mask)
+{
+        struct extent_buffer *eb = NULL;
+        spin_lock(&extent_buffers_lock);
+        if (!list_empty(&extent_buffers)) {
+                eb = list_entry(extent_buffers.next, struct extent_buffer,
+                                list);
+                list_del(&eb->list);
+                WARN_ON(nr_extent_buffers == 0);
+                nr_extent_buffers--;
+        }
+        spin_unlock(&extent_buffers_lock);
+        if (eb) {
+                memset(eb, 0, sizeof(*eb));
+                return eb;
+        }
+        return kmem_cache_zalloc(extent_buffer_cache, mask);
+}
+
+static void __free_extent_buffer(struct extent_buffer *eb)
+{
+        if (nr_extent_buffers >= MAX_EXTENT_BUFFER_CACHE) {
+                kmem_cache_free(extent_buffer_cache, eb);
+        } else {
+                spin_lock(&extent_buffers_lock);
+                list_add(&eb->list, &extent_buffers);
+                nr_extent_buffers++;
+                spin_unlock(&extent_buffers_lock);
+        }
+}
+
+static inline struct page *extent_buffer_page(struct extent_buffer *eb, int i)
+{
+        struct page *p;
+        if (i == 0)
+                return eb->first_page;
+        i += eb->start >> PAGE_CACHE_SHIFT;
+        p = find_get_page(eb->first_page->mapping, i);
+        page_cache_release(p);
+        return p;
+}
+
 struct extent_buffer *alloc_extent_buffer(struct extent_map_tree *tree,
                                           u64 start, unsigned long len,
                                           gfp_t mask)
@@ -1871,7 +1930,7 @@ struct extent_buffer *alloc_extent_buffer(struct extent_map_tree *tree,
         struct address_space *mapping = tree->mapping;
         int uptodate = 0;
 
-        eb = kzalloc(EXTENT_BUFFER_SIZE(num_pages), mask);
+        eb = __alloc_extent_buffer(mask);
         if (!eb || IS_ERR(eb))
                 return NULL;
 
@@ -1881,9 +1940,16 @@ struct extent_buffer *alloc_extent_buffer(struct extent_map_tree *tree,
 
         for (i = 0; i < num_pages; i++, index++) {
                 p = find_or_create_page(mapping, index, mask | __GFP_HIGHMEM);
-                if (!p)
+                if (!p) {
+                        /* make sure the free only frees the pages we've
+                         * grabbed a reference on
+                         */
+                        eb->len = i << PAGE_CACHE_SHIFT;
+                        eb->start &= ~((u64)PAGE_CACHE_SIZE - 1);
                         goto fail;
-                eb->pages[i] = p;
+                }
+                if (i == 0)
+                        eb->first_page = p;
                 if (!PageUptodate(p))
                         uptodate = 0;
                 unlock_page(p);
@@ -1909,7 +1975,7 @@ struct extent_buffer *find_extent_buffer(struct extent_map_tree *tree,
         struct page *p;
         struct address_space *mapping = tree->mapping;
 
-        eb = kzalloc(EXTENT_BUFFER_SIZE(num_pages), mask);
+        eb = __alloc_extent_buffer(mask);
         if (!eb || IS_ERR(eb))
                 return NULL;
 
@@ -1919,9 +1985,16 @@ struct extent_buffer *find_extent_buffer(struct extent_map_tree *tree,
 
         for (i = 0; i < num_pages; i++, index++) {
                 p = find_get_page(mapping, index);
-                if (!p)
+                if (!p) {
+                        /* make sure the free only frees the pages we've
+                         * grabbed a reference on
+                         */
+                        eb->len = i << PAGE_CACHE_SHIFT;
+                        eb->start &= ~((u64)PAGE_CACHE_SIZE - 1);
                         goto fail;
-                eb->pages[i] = p;
+                }
+                if (i == 0)
+                        eb->first_page = p;
         }
         return eb;
 fail:
@@ -1944,11 +2017,12 @@ void free_extent_buffer(struct extent_buffer *eb)
         num_pages = ((eb->start + eb->len - 1) >> PAGE_CACHE_SHIFT) -
                 (eb->start >> PAGE_CACHE_SHIFT) + 1;
 
-        for (i = 0; i < num_pages; i++) {
-                if (eb->pages[i])
-                        page_cache_release(eb->pages[i]);
+        if (eb->first_page)
+                page_cache_release(eb->first_page);
+        for (i = 1; i < num_pages; i++) {
+                page_cache_release(extent_buffer_page(eb, i));
         }
-        kfree(eb);
+        __free_extent_buffer(eb);
 }
 EXPORT_SYMBOL(free_extent_buffer);
 
@@ -1968,7 +2042,7 @@ int clear_extent_buffer_dirty(struct extent_map_tree *tree,
                 (eb->start >> PAGE_CACHE_SHIFT) + 1;
 
         for (i = 0; i < num_pages; i++) {
-                page = eb->pages[i];
+                page = extent_buffer_page(eb, i);
                 lock_page(page);
                 /*
                  * if we're on the last page or the first page and the
@@ -2021,7 +2095,7 @@ int set_extent_buffer_uptodate(struct extent_map_tree *tree,
         set_extent_uptodate(tree, eb->start, eb->start + eb->len - 1,
                             GFP_NOFS);
         for (i = 0; i < num_pages; i++) {
-                page = eb->pages[i];
+                page = extent_buffer_page(eb, i);
                 if ((i == 0 && (eb->start & (PAGE_CACHE_SIZE - 1))) ||
                     ((i == num_pages - 1) &&
                      ((eb->start + eb->len - 1) & (PAGE_CACHE_SIZE - 1)))) {
@@ -2064,7 +2138,7 @@ int read_extent_buffer_pages(struct extent_map_tree *tree,
         num_pages = ((eb->start + eb->len - 1) >> PAGE_CACHE_SHIFT) -
                 (eb->start >> PAGE_CACHE_SHIFT) + 1;
         for (i = 0; i < num_pages; i++) {
-                page = eb->pages[i];
+                page = extent_buffer_page(eb, i);
                 if (PageUptodate(page)) {
                         continue;
                 }
@@ -2090,7 +2164,7 @@ int read_extent_buffer_pages(struct extent_map_tree *tree,
         }
 
         for (i = 0; i < num_pages; i++) {
-                page = eb->pages[i];
+                page = extent_buffer_page(eb, i);
                 wait_on_page_locked(page);
                 if (!PageUptodate(page)) {
                         ret = -EIO;
@@ -2116,12 +2190,12 @@ void read_extent_buffer(struct extent_buffer *eb, void *dstv,
         WARN_ON(start > eb->len);
         WARN_ON(start + len > eb->start + eb->len);
 
-        page = eb->pages[i];
         offset = start & ((unsigned long)PAGE_CACHE_SIZE - 1);
         if (i == 0)
                 offset += start_offset;
 
         while(len > 0) {
+                page = extent_buffer_page(eb, i);
                 WARN_ON(!PageUptodate(page));
 
                 cur = min(len, (PAGE_CACHE_SIZE - offset));
@@ -2134,7 +2208,6 @@ void read_extent_buffer(struct extent_buffer *eb, void *dstv,
                 len -= cur;
                 offset = 0;
                 i++;
-                page = eb->pages[i];
         }
 }
 EXPORT_SYMBOL(read_extent_buffer);
@@ -2165,7 +2238,7 @@ int map_extent_buffer(struct extent_buffer *eb, unsigned long start,
         }
 
         // kaddr = kmap_atomic(eb->pages[i], km);
-        kaddr = page_address(eb->pages[i]);
+        kaddr = page_address(extent_buffer_page(eb, i));
         *token = kaddr;
         *map = kaddr + offset;
         *map_len = PAGE_CACHE_SIZE - offset;
@@ -2195,12 +2268,12 @@ int memcmp_extent_buffer(struct extent_buffer *eb, const void *ptrv,
         WARN_ON(start > eb->len);
         WARN_ON(start + len > eb->start + eb->len);
 
-        page = eb->pages[i];
         offset = start & ((unsigned long)PAGE_CACHE_SIZE - 1);
         if (i == 0)
                 offset += start_offset;
 
         while(len > 0) {
+                page = extent_buffer_page(eb, i);
                 WARN_ON(!PageUptodate(page));
 
                 cur = min(len, (PAGE_CACHE_SIZE - offset));
@@ -2216,7 +2289,6 @@ int memcmp_extent_buffer(struct extent_buffer *eb, const void *ptrv,
                 len -= cur;
                 offset = 0;
                 i++;
-                page = eb->pages[i];
         }
         return ret;
 }
@@ -2236,12 +2308,12 @@ void write_extent_buffer(struct extent_buffer *eb, const void *srcv,
         WARN_ON(start > eb->len);
         WARN_ON(start + len > eb->start + eb->len);
 
-        page = eb->pages[i];
         offset = start & ((unsigned long)PAGE_CACHE_SIZE - 1);
         if (i == 0)
                 offset += start_offset;
 
         while(len > 0) {
+                page = extent_buffer_page(eb, i);
                 WARN_ON(!PageUptodate(page));
 
                 cur = min(len, PAGE_CACHE_SIZE - offset);
@@ -2254,7 +2326,6 @@ void write_extent_buffer(struct extent_buffer *eb, const void *srcv,
                 len -= cur;
                 offset = 0;
                 i++;
-                page = eb->pages[i];
         }
 }
 EXPORT_SYMBOL(write_extent_buffer);
@@ -2272,12 +2343,12 @@ void memset_extent_buffer(struct extent_buffer *eb, char c,
         WARN_ON(start > eb->len);
         WARN_ON(start + len > eb->start + eb->len);
 
-        page = eb->pages[i];
         offset = start & ((unsigned long)PAGE_CACHE_SIZE - 1);
         if (i == 0)
                 offset += start_offset;
 
         while(len > 0) {
+                page = extent_buffer_page(eb, i);
                 WARN_ON(!PageUptodate(page));
 
                 cur = min(len, PAGE_CACHE_SIZE - offset);
@@ -2289,7 +2360,6 @@ void memset_extent_buffer(struct extent_buffer *eb, char c,
                 len -= cur;
                 offset = 0;
                 i++;
-                page = eb->pages[i];
         }
 }
 EXPORT_SYMBOL(memset_extent_buffer);
@@ -2313,7 +2383,7 @@ void copy_extent_buffer(struct extent_buffer *dst, struct extent_buffer *src,
                 offset += start_offset;
 
         while(len > 0) {
-                page = dst->pages[i];
+                page = extent_buffer_page(dst, i);
                 WARN_ON(!PageUptodate(page));
 
                 cur = min(len, (unsigned long)(PAGE_CACHE_SIZE - offset));
@@ -2414,7 +2484,8 @@ void memcpy_extent_buffer(struct extent_buffer *dst, unsigned long dst_offset,
                 cur = min(cur, (unsigned long)(PAGE_CACHE_SIZE -
                                                dst_off_in_page));
 
-                copy_pages(dst->pages[dst_i], dst->pages[src_i],
+                copy_pages(extent_buffer_page(dst, dst_i),
+                           extent_buffer_page(dst, src_i),
                            dst_off_in_page, src_off_in_page, cur);
 
                 src_offset += cur;
@@ -2467,7 +2538,8 @@ void memmove_extent_buffer(struct extent_buffer *dst, unsigned long dst_offset,
                 cur = min(len, src_off_in_page + 1);
                 cur = min(cur, dst_off_in_page + 1);
 // printk("move pages orig dst %lu src %lu len %lu, this %lu %lu %lu\n", dst_offset, src_offset, len, dst_off_in_page - cur + 1, src_off_in_page - cur + 1, cur);
-                move_pages(dst->pages[dst_i], dst->pages[src_i],
+                move_pages(extent_buffer_page(dst, dst_i),
+                           extent_buffer_page(dst, src_i),
                            dst_off_in_page - cur + 1,
                            src_off_in_page - cur + 1, cur);