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-rw-r--r--mm/readahead.c20
1 files changed, 14 insertions, 6 deletions
diff --git a/mm/readahead.c b/mm/readahead.c
index c6ffb76827da..c5b0457415be 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -552,15 +552,23 @@ readit:
void page_cache_sync_ra(struct readahead_control *ractl,
struct file_ra_state *ra, unsigned long req_count)
{
- /* no read-ahead */
- if (!ra->ra_pages)
- return;
+ bool do_forced_ra = ractl->file && (ractl->file->f_mode & FMODE_RANDOM);
- if (blk_cgroup_congested())
- return;
+ /*
+ * Even if read-ahead is disabled, issue this request as read-ahead
+ * as we'll need it to satisfy the requested range. The forced
+ * read-ahead will do the right thing and limit the read to just the
+ * requested range, which we'll set to 1 page for this case.
+ */
+ if (!ra->ra_pages || blk_cgroup_congested()) {
+ if (!ractl->file)
+ return;
+ req_count = 1;
+ do_forced_ra = true;
+ }
/* be dumb */
- if (ractl->file && (ractl->file->f_mode & FMODE_RANDOM)) {
+ if (do_forced_ra) {
force_page_cache_ra(ractl, ra, req_count);
return;
}