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Date: Sun, 12 May 2013 04:23:31 +0300
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: Andrea Arcangeli <aarcange@...hat.com>,
Andrew Morton <akpm@...ux-foundation.org>
Cc: Al Viro <viro@...iv.linux.org.uk>, Hugh Dickins <hughd@...gle.com>,
Wu Fengguang <fengguang.wu@...el.com>, Jan Kara <jack@...e.cz>,
Mel Gorman <mgorman@...e.de>, linux-mm@...ck.org,
Andi Kleen <ak@...ux.intel.com>,
Matthew Wilcox <matthew.r.wilcox@...el.com>,
"Kirill A. Shutemov" <kirill@...temov.name>,
Hillf Danton <dhillf@...il.com>, Dave Hansen <dave@...1.net>,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: [PATCHv4 34/39] thp, mm: handle huge pages in filemap_fault()
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
If caller asks for huge page (flags & FAULT_FLAG_TRANSHUGE),
filemap_fault() return it if there's a huge page already by the offset.
If the area of page cache required to create huge is empty, we create a
new huge page and return it.
Otherwise we return VM_FAULT_FALLBACK to indicate that fallback to small
pages is required.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
---
mm/filemap.c | 52 +++++++++++++++++++++++++++++++++++++++++++---------
1 file changed, 43 insertions(+), 9 deletions(-)
diff --git a/mm/filemap.c b/mm/filemap.c
index 9877347..1deedd6 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -1557,14 +1557,23 @@ EXPORT_SYMBOL(generic_file_aio_read);
* This adds the requested page to the page cache if it isn't already there,
* and schedules an I/O to read in its contents from disk.
*/
-static int page_cache_read(struct file *file, pgoff_t offset)
+static int page_cache_read(struct file *file, pgoff_t offset, bool thp)
{
struct address_space *mapping = file->f_mapping;
- struct page *page;
+ struct page *page;
int ret;
do {
- page = page_cache_alloc_cold(mapping);
+ if (thp) {
+ gfp_t gfp_mask = mapping_gfp_mask(mapping) | __GFP_COLD;
+ BUG_ON(offset & HPAGE_CACHE_INDEX_MASK);
+ page = alloc_pages(gfp_mask, HPAGE_PMD_ORDER);
+ if (page)
+ count_vm_event(THP_FAULT_ALLOC);
+ else
+ count_vm_event(THP_FAULT_FALLBACK);
+ } else
+ page = page_cache_alloc_cold(mapping);
if (!page)
return -ENOMEM;
@@ -1573,11 +1582,18 @@ static int page_cache_read(struct file *file, pgoff_t offset)
ret = mapping->a_ops->readpage(file, page);
else if (ret == -EEXIST)
ret = 0; /* losing race to add is OK */
+ else if (ret == -ENOSPC)
+ /*
+ * No space in page cache to add huge page.
+ * For caller it's the same as -ENOMEM: fall back to
+ * small pages is required.
+ */
+ ret = -ENOMEM;
page_cache_release(page);
} while (ret == AOP_TRUNCATED_PAGE);
-
+
return ret;
}
@@ -1669,13 +1685,20 @@ int filemap_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
struct address_space *mapping = file->f_mapping;
struct file_ra_state *ra = &file->f_ra;
struct inode *inode = mapping->host;
+ bool thp = vmf->flags & FAULT_FLAG_TRANSHUGE;
pgoff_t offset = vmf->pgoff;
+ unsigned long address = (unsigned long)vmf->virtual_address;
struct page *page;
pgoff_t size;
int ret = 0;
+ if (thp) {
+ BUG_ON(ra->ra_pages);
+ offset = linear_page_index(vma, address & HPAGE_PMD_MASK);
+ }
+
size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
- if (offset >= size)
+ if (vmf->pgoff >= size)
return VM_FAULT_SIGBUS;
/*
@@ -1700,7 +1723,8 @@ retry_find:
goto no_cached_page;
}
- if (PageTransCompound(page))
+ /* Split huge page if we don't want huge page to be here */
+ if (!thp && PageTransCompound(page))
split_huge_page(compound_trans_head(page));
if (!lock_page_or_retry(page, vma->vm_mm, vmf->flags)) {
page_cache_release(page);
@@ -1722,12 +1746,22 @@ retry_find:
if (unlikely(!PageUptodate(page)))
goto page_not_uptodate;
+ if (thp && !PageTransHuge(page)) {
+ /*
+ * Caller asked for huge page, but we have small page
+ * by this offset. Fallback to small pages.
+ */
+ unlock_page(page);
+ page_cache_release(page);
+ return VM_FAULT_FALLBACK;
+ }
+
/*
* Found the page and have a reference on it.
* We must recheck i_size under page lock.
*/
size = (i_size_read(inode) + PAGE_CACHE_SIZE - 1) >> PAGE_CACHE_SHIFT;
- if (unlikely(offset >= size)) {
+ if (unlikely(vmf->pgoff >= size)) {
unlock_page(page);
page_cache_release(page);
return VM_FAULT_SIGBUS;
@@ -1741,7 +1775,7 @@ no_cached_page:
* We're only likely to ever get here if MADV_RANDOM is in
* effect.
*/
- error = page_cache_read(file, offset);
+ error = page_cache_read(file, offset, thp);
/*
* The page we want has now been added to the page cache.
@@ -1757,7 +1791,7 @@ no_cached_page:
* to schedule I/O.
*/
if (error == -ENOMEM)
- return VM_FAULT_OOM;
+ return VM_FAULT_OOM | VM_FAULT_FALLBACK;
return VM_FAULT_SIGBUS;
page_not_uptodate:
--
1.7.10.4
--
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