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authorChristoph Hellwig <hch@lst.de>2018-06-01 09:03:06 -0700
committerDarrick J. Wong <darrick.wong@oracle.com>2018-06-01 18:37:32 -0700
commitb3751e6ab45a3b92da1e4acd42ada7b6a4122f2b (patch)
tree89da8a8cbe40bb7258ec11861e3b4f18db026537 /mm/readahead.c
parentc534aa3fdd149fab18b094375f334b4bb3635cbf (diff)
downloadlinux-b3751e6ab45a3b92da1e4acd42ada7b6a4122f2b.tar.bz2
mm: split ->readpages calls to avoid non-contiguous pages lists
That way file systems don't have to go spotting for non-contiguous pages and work around them. It also kicks off I/O earlier, allowing it to finish earlier and reduce latency. Signed-off-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Dave Chinner <dchinner@redhat.com> Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com> Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
Diffstat (limited to 'mm/readahead.c')
-rw-r--r--mm/readahead.c16
1 files changed, 13 insertions, 3 deletions
diff --git a/mm/readahead.c b/mm/readahead.c
index fa4d4b767130..e273f0de3376 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -140,8 +140,8 @@ out:
}
/*
- * __do_page_cache_readahead() actually reads a chunk of disk. It allocates all
- * the pages first, then submits them all for I/O. This avoids the very bad
+ * __do_page_cache_readahead() actually reads a chunk of disk. It allocates
+ * the pages first, then submits them for I/O. This avoids the very bad
* behaviour which would occur if page allocations are causing VM writeback.
* We really don't want to intermingle reads and writes like that.
*
@@ -177,8 +177,18 @@ unsigned int __do_page_cache_readahead(struct address_space *mapping,
rcu_read_lock();
page = radix_tree_lookup(&mapping->i_pages, page_offset);
rcu_read_unlock();
- if (page && !radix_tree_exceptional_entry(page))
+ if (page && !radix_tree_exceptional_entry(page)) {
+ /*
+ * Page already present? Kick off the current batch of
+ * contiguous pages before continuing with the next
+ * batch.
+ */
+ if (nr_pages)
+ read_pages(mapping, filp, &page_pool, nr_pages,
+ gfp_mask);
+ nr_pages = 0;
continue;
+ }
page = __page_cache_alloc(gfp_mask);
if (!page)