readahead: combine file_ra_state.prev_index/prev_offset into prev_pos

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

diff --git a/mm/readahead.c b/mm/readahead.c
index d250487..4a58bef 100644 (file)
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -46,7 +46,7 @@ void
 file_ra_state_init(struct file_ra_state *ra, struct address_space *mapping)
 {
        ra->ra_pages = mapping->backing_dev_info->ra_pages;
-       ra->prev_index = -1;
+       ra->prev_pos = -1;
 }
 EXPORT_SYMBOL_GPL(file_ra_state_init);
 
@@ -327,7 +327,7 @@ static unsigned long get_next_ra_size(struct file_ra_state *ra,
  * indicator. The flag won't be set on already cached pages, to avoid the
  * readahead-for-nothing fuss, saving pointless page cache lookups.
  *
- * prev_index tracks the last visited page in the _previous_ read request.
+ * prev_pos tracks the last visited byte in the _previous_ read request.
  * It should be maintained by the caller, and will be used for detecting
  * small random reads. Note that the readahead algorithm checks loosely
  * for sequential patterns. Hence interleaved reads might be served as
@@ -351,11 +351,9 @@ ondemand_readahead(struct address_space *mapping,
                   bool hit_readahead_marker, pgoff_t offset,
                   unsigned long req_size)
 {
-       int max;        /* max readahead pages */
-       int sequential;
-
-       max = ra->ra_pages;
-       sequential = (offset - ra->prev_index <= 1UL) || (req_size > max);
+       int     max = ra->ra_pages;     /* max readahead pages */
+       pgoff_t prev_offset;
+       int     sequential;
 
        /*
         * It's the expected callback offset, assume sequential access.
@@ -369,6 +367,9 @@ ondemand_readahead(struct address_space *mapping,
                goto readit;
        }
 
+       prev_offset = ra->prev_pos >> PAGE_CACHE_SHIFT;
+       sequential = offset - prev_offset <= 1UL || req_size > max;
+
        /*
         * Standalone, small read.
         * Read as is, and do not pollute the readahead state.