linux-kernel - [PATCH 66/71] hugetlb: get rid of PAGE_CACHE_* and page_cache

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Date:	Sun, 20 Mar 2016 21:41:13 +0300
From:	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To:	Andrew Morton <akpm@...ux-foundation.org>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Christoph Lameter <cl@...ux.com>,
	Matthew Wilcox <willy@...ux.intel.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	linux-fsdevel@...r.kernel.org,
	"Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
	Nadia Yvette Chambers <nyc@...omorphy.com>
Subject: [PATCH 66/71] hugetlb: get rid of PAGE_CACHE_* and page_cache_{get,release} macros

PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} macros were introduced *long* time ago
with promise that one day it will be possible to implement page cache with
bigger chunks than PAGE_SIZE.

This promise never materialized. And unlikely will.

We have many places where PAGE_CACHE_SIZE assumed to be equal to
PAGE_SIZE. And it's constant source of confusion on whether PAGE_CACHE_*
or PAGE_* constant should be used in a particular case, especially on the
border between fs and mm.

Global switching to PAGE_CACHE_SIZE != PAGE_SIZE would cause to much
breakage to be doable.

Let's stop pretending that pages in page cache are special. They are not.

The changes are pretty straight-forward:

 - <foo> << (PAGE_CACHE_SHIFT - PAGE_SHIFT) -> <foo>;

 - PAGE_CACHE_{SIZE,SHIFT,MASK,ALIGN} -> PAGE_{SIZE,SHIFT,MASK,ALIGN};

 - page_cache_get() -> get_page();

 - page_cache_release() -> put_page();

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Cc: Nadia Yvette Chambers <nyc@...omorphy.com>
---
 fs/hugetlbfs/inode.c | 10 +++++-----
 mm/hugetlb.c         |  8 ++++----
 2 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index e1f465a389d5..4ea71eba40a5 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -213,12 +213,12 @@ hugetlbfs_read_actor(struct page *page, unsigned long offset,
 	int i, chunksize;
 
 	/* Find which 4k chunk and offset with in that chunk */
-	i = offset >> PAGE_CACHE_SHIFT;
-	offset = offset & ~PAGE_CACHE_MASK;
+	i = offset >> PAGE_SHIFT;
+	offset = offset & ~PAGE_MASK;
 
 	while (size) {
 		size_t n;
-		chunksize = PAGE_CACHE_SIZE;
+		chunksize = PAGE_SIZE;
 		if (offset)
 			chunksize -= offset;
 		if (chunksize > size)
@@ -237,7 +237,7 @@ hugetlbfs_read_actor(struct page *page, unsigned long offset,
 /*
  * Support for read() - Find the page attached to f_mapping and copy out the
  * data. Its *very* similar to do_generic_mapping_read(), we can't use that
- * since it has PAGE_CACHE_SIZE assumptions.
+ * since it has PAGE_SIZE assumptions.
  */
 static ssize_t hugetlbfs_read_iter(struct kiocb *iocb, struct iov_iter *to)
 {
@@ -285,7 +285,7 @@ static ssize_t hugetlbfs_read_iter(struct kiocb *iocb, struct iov_iter *to)
 			 * We have the page, copy it to user space buffer.
 			 */
 			copied = hugetlbfs_read_actor(page, offset, to, nr);
-			page_cache_release(page);
+			put_page(page);
 		}
 		offset += copied;
 		retval += copied;
diff --git a/mm/hugetlb.c b/mm/hugetlb.c
index 06058eaa173b..19d0d08b396f 100644
--- a/mm/hugetlb.c
+++ b/mm/hugetlb.c
@@ -3346,7 +3346,7 @@ retry_avoidcopy:
 			old_page != pagecache_page)
 		outside_reserve = 1;
 
-	page_cache_get(old_page);
+	get_page(old_page);
 
 	/*
 	 * Drop page table lock as buddy allocator may be called. It will
@@ -3364,7 +3364,7 @@ retry_avoidcopy:
 		 * may get SIGKILLed if it later faults.
 		 */
 		if (outside_reserve) {
-			page_cache_release(old_page);
+			put_page(old_page);
 			BUG_ON(huge_pte_none(pte));
 			unmap_ref_private(mm, vma, old_page, address);
 			BUG_ON(huge_pte_none(pte));
@@ -3425,9 +3425,9 @@ retry_avoidcopy:
 	spin_unlock(ptl);
 	mmu_notifier_invalidate_range_end(mm, mmun_start, mmun_end);
 out_release_all:
-	page_cache_release(new_page);
+	put_page(new_page);
 out_release_old:
-	page_cache_release(old_page);
+	put_page(old_page);
 
 	spin_lock(ptl); /* Caller expects lock to be held */
 	return ret;
-- 
2.7.0