Btrfs: Add readpages support

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

3 files changed, 78 insertions, 8 deletions

diff --git a/fs/btrfs/extent_map.c b/fs/btrfs/extent_map.c
index 754bc42c162a..0077c6c1d9f9 100644
--- a/fs/btrfs/extent_map.c
+++ b/fs/btrfs/extent_map.c
@@ -11,6 +11,7 @@
 #include <linux/swap.h>
 #include <linux/version.h>
 #include <linux/writeback.h>
+#include <linux/pagevec.h>
 #include "extent_map.h"
 
 /* temporary define until extent_map moves out of btrfs */
@@ -1503,7 +1504,7 @@ static int submit_extent_page(int rw, struct extent_map_tree *tree,
                               size_t size, unsigned long offset,
                               struct block_device *bdev,
                               struct bio **bio_ret,
-                              int max_pages,
+                              unsigned long max_pages,
                               bio_end_io_t end_io_func)
 {
         int ret = 0;
@@ -1520,7 +1521,7 @@ static int submit_extent_page(int rw, struct extent_map_tree *tree,
                         return 0;
                 }
         }
-        nr = min(max_pages, bio_get_nr_vecs(bdev));
+        nr = min_t(int, max_pages, bio_get_nr_vecs(bdev));
         bio = extent_bio_alloc(bdev, sector, nr, GFP_NOFS | __GFP_HIGH);
         if (!bio) {
                 printk("failed to allocate bio nr %d\n", nr);
@@ -1552,8 +1553,10 @@ void set_page_extent_mapped(struct page *page)
  * into the tree that are removed when the IO is done (by the end_io
  * handlers)
  */
-int extent_read_full_page(struct extent_map_tree *tree, struct page *page,
-                          get_extent_t *get_extent)
+static int __extent_read_full_page(struct extent_map_tree *tree,
+                                   struct page *page,
+                                   get_extent_t *get_extent,
+                                   struct bio **bio)
 {
         struct inode *inode = page->mapping->host;
         u64 start = (u64)page->index << PAGE_CACHE_SHIFT;
@@ -1631,10 +1634,12 @@ int extent_read_full_page(struct extent_map_tree *tree, struct page *page,
                                                           cur + iosize - 1);
                 }
                 if (!ret) {
+                        unsigned long nr = (last_byte >> PAGE_CACHE_SHIFT) + 1;
+                        nr -= page->index;
                         ret = submit_extent_page(READ, tree, page,
-                                                 sector, iosize, page_offset,
-                                                 bdev, NULL, 1,
-                                                 end_bio_extent_readpage);
+                                         sector, iosize, page_offset,
+                                         bdev, bio, nr,
+                                         end_bio_extent_readpage);
                 }
                 if (ret)
                         SetPageError(page);
@@ -1649,6 +1654,18 @@ int extent_read_full_page(struct extent_map_tree *tree, struct page *page,
         }
         return 0;
 }
+
+int extent_read_full_page(struct extent_map_tree *tree, struct page *page,
+                            get_extent_t *get_extent)
+{
+        struct bio *bio = NULL;
+        int ret;
+
+        ret = __extent_read_full_page(tree, page, get_extent, &bio);
+        if (bio)
+                submit_one_bio(READ, bio);
+        return ret;
+}
 EXPORT_SYMBOL(extent_read_full_page);
 
 /*
@@ -1836,6 +1853,45 @@ int extent_writepages(struct extent_map_tree *tree,
 }
 EXPORT_SYMBOL(extent_writepages);
 
+int extent_readpages(struct extent_map_tree *tree,
+                     struct address_space *mapping,
+                     struct list_head *pages, unsigned nr_pages,
+                     get_extent_t get_extent)
+{
+        struct bio *bio = NULL;
+        unsigned page_idx;
+        struct pagevec pvec;
+
+        pagevec_init(&pvec, 0);
+        for (page_idx = 0; page_idx < nr_pages; page_idx++) {
+                struct page *page = list_entry(pages->prev, struct page, lru);
+
+                prefetchw(&page->flags);
+                list_del(&page->lru);
+                /*
+                 * what we want to do here is call add_to_page_cache_lru,
+                 * but that isn't exported, so we reproduce it here
+                 */
+                if (!add_to_page_cache(page, mapping,
+                                        page->index, GFP_KERNEL)) {
+
+                        /* open coding of lru_cache_add, also not exported */
+                        page_cache_get(page);
+                        if (!pagevec_add(&pvec, page))
+                                __pagevec_lru_add(&pvec);
+                        __extent_read_full_page(tree, page, get_extent, &bio);
+                }
+                page_cache_release(page);
+        }
+        if (pagevec_count(&pvec))
+                __pagevec_lru_add(&pvec);
+        BUG_ON(!list_empty(pages));
+        if (bio)
+                submit_one_bio(READ, bio);
+        return 0;
+}
+EXPORT_SYMBOL(extent_readpages);
+
 /*
  * basic invalidatepage code, this waits on any locked or writeback
  * ranges corresponding to the page, and then deletes any extent state
diff --git a/fs/btrfs/extent_map.h b/fs/btrfs/extent_map.h
index 0b0dcf19fe45..fbd23a72f53b 100644
--- a/fs/btrfs/extent_map.h
+++ b/fs/btrfs/extent_map.h
@@ -140,6 +140,10 @@ int extent_writepages(struct extent_map_tree *tree,
                       struct address_space *mapping,
                       get_extent_t *get_extent,
                       struct writeback_control *wbc);
+int extent_readpages(struct extent_map_tree *tree,
+                     struct address_space *mapping,
+                     struct list_head *pages, unsigned nr_pages,
+                     get_extent_t get_extent);
 int extent_prepare_write(struct extent_map_tree *tree,
                          struct inode *inode, struct page *page,
                          unsigned from, unsigned to, get_extent_t *get_extent);
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 90cb71d68294..d6d32465bc9a 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1748,7 +1748,6 @@ static int btrfs_writepage(struct page *page, struct writeback_control *wbc)
         return extent_write_full_page(tree, page, btrfs_get_extent, wbc);
 }
 
-
 static int btrfs_writepages(struct address_space *mapping,
                             struct writeback_control *wbc)
 {
@@ -1757,6 +1756,16 @@ static int btrfs_writepages(struct address_space *mapping,
         return extent_writepages(tree, mapping, btrfs_get_extent, wbc);
 }
 
+static int
+btrfs_readpages(struct file *file, struct address_space *mapping,
+                struct list_head *pages, unsigned nr_pages)
+{
+        struct extent_map_tree *tree;
+        tree = &BTRFS_I(mapping->host)->extent_tree;
+        return extent_readpages(tree, mapping, pages, nr_pages,
+                                btrfs_get_extent);
+}
+
 static int btrfs_releasepage(struct page *page, gfp_t unused_gfp_flags)
 {
         struct extent_map_tree *tree;
@@ -2537,6 +2546,7 @@ static struct address_space_operations btrfs_aops = {
         .readpage       = btrfs_readpage,
         .writepage      = btrfs_writepage,
         .writepages     = btrfs_writepages,
+        .readpages      = btrfs_readpages,
         .sync_page      = block_sync_page,
         .prepare_write  = btrfs_prepare_write,
         .commit_write   = btrfs_commit_write,