try_context_readahead() has a single caller page_cache_sync_ra(). Fold
the function there to make ra state modifications more obvious. No
functional changes.
Signed-off-by: Jan Kara <jack@xxxxxxx>
---
mm/readahead.c | 84 +++++++++++++-------------------------------------
1 file changed, 22 insertions(+), 62 deletions(-)
diff --git a/mm/readahead.c b/mm/readahead.c
index a44daa12ebd2..12c0d2215329 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -410,58 +410,6 @@ static unsigned long get_next_ra_size(struct file_ra_state *ra,
* it approaches max_readhead.
*/
-/*
- * Count contiguously cached pages from @index-1 to @index-@max,
- * this count is a conservative estimation of
- * - length of the sequential read sequence, or
- * - thrashing threshold in memory tight systems
- */
-static pgoff_t count_history_pages(struct address_space *mapping,
- pgoff_t index, unsigned long max)
-{
- pgoff_t head;
-
- rcu_read_lock();
- head = page_cache_prev_miss(mapping, index - 1, max);
- rcu_read_unlock();
-
- return index - 1 - head;
-}
-
-/*
- * page cache context based readahead
- */
-static int try_context_readahead(struct address_space *mapping,
- struct file_ra_state *ra,
- pgoff_t index,
- unsigned long req_size,
- unsigned long max)
-{
- pgoff_t size;
-
- size = count_history_pages(mapping, index, max);
-
- /*
- * not enough history pages:
- * it could be a random read
- */
- if (size <= req_size)
- return 0;
-
- /*
- * starts from beginning of file:
- * it is a strong indication of long-run stream (or whole-file-read)
- */
- if (size >= index)
- size *= 2;
-
- ra->start = index;
- ra->size = min(size + req_size, max);
- ra->async_size = 1;
-
- return 1;
-}
-
static inline int ra_alloc_folio(struct readahead_control *ractl, pgoff_t index,
pgoff_t mark, unsigned int order, gfp_t gfp)
{
@@ -561,8 +509,8 @@ void page_cache_sync_ra(struct readahead_control *ractl,
pgoff_t index = readahead_index(ractl);
bool do_forced_ra = ractl->file && (ractl->file->f_mode & FMODE_RANDOM);
struct file_ra_state *ra = ractl->ra;
- unsigned long max_pages;
- pgoff_t prev_index;
+ unsigned long max_pages, contig_count;
+ pgoff_t prev_index, miss;
/*
* Even if readahead is disabled, issue this request as readahead
@@ -603,16 +551,28 @@ void page_cache_sync_ra(struct readahead_control *ractl,
* Query the page cache and look for the traces(cached history pages)
* that a sequential stream would leave behind.
*/
- if (try_context_readahead(ractl->mapping, ra, index, req_count,
- max_pages))
- goto readit;
-
+ rcu_read_lock();
+ miss = page_cache_prev_miss(ractl->mapping, index - 1, max_pages);
+ rcu_read_unlock();
+ contig_count = index - miss - 1;
/*
- * standalone, small random read
- * Read as is, and do not pollute the readahead state.
+ * Standalone, small random read. Read as is, and do not pollute the
+ * readahead state.
*/
- do_page_cache_ra(ractl, req_count, 0);
- return;
+ if (contig_count <= req_count) {
+ do_page_cache_ra(ractl, req_count, 0);
+ return;
+ }
+ /*
+ * File cached from the beginning:
+ * it is a strong indication of long-run stream (or whole-file-read)
+ */
+ if (miss == ULONG_MAX)
+ contig_count *= 2;
+ ra->start = index;
+ ra->size = min(contig_count + req_count, max_pages);
+ ra->async_size = 1;
+ goto readit;
initial_readahead:
ra->start = index;
--
2.35.3
