From f615bfca468c9b80ed2d09be5fdbaf470a32c045 Mon Sep 17 00:00:00 2001 From: Fengguang Wu Date: Thu, 19 Jul 2007 01:47:58 -0700 Subject: readahead: MIN_RA_PAGES/MAX_RA_PAGES macros Define two convenient macros for read-ahead: - MAX_RA_PAGES: rounded down counterpart of VM_MAX_READAHEAD - MIN_RA_PAGES: rounded _up_ counterpart of VM_MIN_READAHEAD Note that the rounded up MIN_RA_PAGES will work flawlessly with _large_ page sizes like 64k. Signed-off-by: Fengguang Wu Cc: Steven Pratt Cc: Ram Pai Cc: Rusty Russell Cc: Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/readahead.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) (limited to 'mm/readahead.c') diff --git a/mm/readahead.c b/mm/readahead.c index 88ea0f2..7f9bf58 100644 --- 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) -- cgit v1.1