readahead: basic support of interleaved reads

[linux-2.6-omap-h63xx.git] / mm / readahead.c

diff --git a/mm/readahead.c b/mm/readahead.c
index 4a58befbde4a5f157f6c5372d0420ea9c5390e71..fd588ffc508637d8bbf17b9905e24e509aa42369 100644 (file)
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -379,6 +379,29 @@ ondemand_readahead(struct address_space *mapping,
                                                offset, req_size, 0);
        }
 
+       /*
+        * Hit a marked page without valid readahead state.
+        * E.g. interleaved reads.
+        * Query the pagecache for async_size, which normally equals to
+        * readahead size. Ramp it up and use it as the new readahead size.
+        */
+       if (hit_readahead_marker) {
+               pgoff_t start;
+
+               read_lock_irq(&mapping->tree_lock);
+               start = radix_tree_next_hole(&mapping->page_tree, offset, max+1);
+               read_unlock_irq(&mapping->tree_lock);
+
+               if (!start || start - offset > max)
+                       return 0;
+
+               ra->start = start;
+               ra->size = start - offset;      /* old async_size */
+               ra->size = get_next_ra_size(ra, max);
+               ra->async_size = ra->size;
+               goto readit;
+       }
+
        /*
         * It may be one of
         *      - first read on start of file
@@ -390,16 +413,6 @@ ondemand_readahead(struct address_space *mapping,
        ra->size = get_init_ra_size(req_size, max);
        ra->async_size = ra->size > req_size ? ra->size - req_size : ra->size;
 
-       /*
-        * Hit on a marked page without valid readahead state.
-        * E.g. interleaved reads.
-        * Not knowing its readahead pos/size, bet on the minimal possible one.
-        */
-       if (hit_readahead_marker) {
-               ra->start++;
-               ra->size = get_next_ra_size(ra, max);
-       }
-
 readit:
        return ra_submit(ra, mapping, filp);
 }