readahead: MIN_RA_PAGES/MAX_RA_PAGES macros

[pandora-kernel.git] / mm / readahead.c

diff --git a/mm/readahead.c b/mm/readahead.c
index 88ea0f2..7f9bf58 100644 (file)
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -21,8 +21,16 @@ void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page)
 }
 EXPORT_SYMBOL(default_unplug_io_fn);
 
+/*
+ * Convienent macros for min/max read-ahead pages.
+ * Note that MAX_RA_PAGES is rounded down, while MIN_RA_PAGES is rounded up.
+ * The latter is necessary for systems with large page size(i.e. 64k).
+ */
+#define MAX_RA_PAGES   (VM_MAX_READAHEAD*1024 / PAGE_CACHE_SIZE)
+#define MIN_RA_PAGES   DIV_ROUND_UP(VM_MIN_READAHEAD*1024, PAGE_CACHE_SIZE)
+
 struct backing_dev_info default_backing_dev_info = {
-       .ra_pages       = (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE,
+       .ra_pages       = MAX_RA_PAGES,
        .state          = 0,
        .capabilities   = BDI_CAP_MAP_COPY,
        .unplug_io_fn   = default_unplug_io_fn,
@@ -51,7 +59,7 @@ static inline unsigned long get_max_readahead(struct file_ra_state *ra)
 
 static inline unsigned long get_min_readahead(struct file_ra_state *ra)
 {
-       return (VM_MIN_READAHEAD * 1024) / PAGE_CACHE_SIZE;
+       return MIN_RA_PAGES;
 }
 
 static inline void reset_ahead_window(struct file_ra_state *ra)