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-rw-r--r--mm/readahead.c39
1 files changed, 22 insertions, 17 deletions
diff --git a/mm/readahead.c b/mm/readahead.c
index 539bbb6c1fad..e273f0de3376 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -140,23 +140,23 @@ 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.
*
* Returns the number of pages requested, or the maximum amount of I/O allowed.
*/
-int __do_page_cache_readahead(struct address_space *mapping, struct file *filp,
- pgoff_t offset, unsigned long nr_to_read,
- unsigned long lookahead_size)
+unsigned int __do_page_cache_readahead(struct address_space *mapping,
+ struct file *filp, pgoff_t offset, unsigned long nr_to_read,
+ unsigned long lookahead_size)
{
struct inode *inode = mapping->host;
struct page *page;
unsigned long end_index; /* The last page we want to read */
LIST_HEAD(page_pool);
int page_idx;
- int ret = 0;
+ unsigned int nr_pages = 0;
loff_t isize = i_size_read(inode);
gfp_t gfp_mask = readahead_gfp_mask(mapping);
@@ -177,8 +177,18 @@ int __do_page_cache_readahead(struct address_space *mapping, struct file *filp,
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)
@@ -187,7 +197,7 @@ int __do_page_cache_readahead(struct address_space *mapping, struct file *filp,
list_add(&page->lru, &page_pool);
if (page_idx == nr_to_read - lookahead_size)
SetPageReadahead(page);
- ret++;
+ nr_pages++;
}
/*
@@ -195,11 +205,11 @@ int __do_page_cache_readahead(struct address_space *mapping, struct file *filp,
* uptodate then the caller will launch readpage again, and
* will then handle the error.
*/
- if (ret)
- read_pages(mapping, filp, &page_pool, ret, gfp_mask);
+ if (nr_pages)
+ read_pages(mapping, filp, &page_pool, nr_pages, gfp_mask);
BUG_ON(!list_empty(&page_pool));
out:
- return ret;
+ return nr_pages;
}
/*
@@ -223,16 +233,11 @@ int force_page_cache_readahead(struct address_space *mapping, struct file *filp,
max_pages = max_t(unsigned long, bdi->io_pages, ra->ra_pages);
nr_to_read = min(nr_to_read, max_pages);
while (nr_to_read) {
- int err;
-
unsigned long this_chunk = (2 * 1024 * 1024) / PAGE_SIZE;
if (this_chunk > nr_to_read)
this_chunk = nr_to_read;
- err = __do_page_cache_readahead(mapping, filp,
- offset, this_chunk, 0);
- if (err < 0)
- return err;
+ __do_page_cache_readahead(mapping, filp, offset, this_chunk, 0);
offset += this_chunk;
nr_to_read -= this_chunk;