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btrfs: allocate page arrays using bulk page allocator

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While calling alloc_page() in a loop is an effective way to populate an
array of pages, the MM subsystem provides a method to allocate pages in
bulk.  alloc_pages_bulk_array() populates the NULL slots in a page
array, trying to grab more than one page at a time.

Unfortunately, it doesn't guarantee allocating all slots in the array,
but it's easy to call it in a loop and return an error if no progress
occurs.

Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Sweet Tea Dorminy <sweettea-kernel@dorminy.me>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Sweet Tea Dorminy 2022-03-30 16:11:23 -04:00 committed by David Sterba
parent dd137dd1f2
commit 91d6ac1d62
1 changed files with 11 additions and 8 deletions
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19
fs/btrfs/extent_io.c
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@ -3146,17 +3146,20 @@ static void end_bio_extent_readpage(struct bio *bio)
*/
int btrfs_alloc_page_array(unsigned int nr_pages, struct page **page_array)
{
int i;
unsigned int allocated;
for (i = 0; i < nr_pages; i++) {
struct page *page;
for (allocated = 0; allocated < nr_pages;) {
unsigned int last = allocated;
if (page_array[i])
continue;
page = alloc_page(GFP_NOFS);
if (!page)
allocated = alloc_pages_bulk_array(GFP_NOFS, nr_pages, page_array);
/*
* During this iteration, no page could be allocated, even
* though alloc_pages_bulk_array() falls back to alloc_page()
* if it could not bulk-allocate. So we must be out of memory.
*/
if (allocated == last)
return -ENOMEM;
page_array[i] = page;
}
return 0;
}