linux-kernel - [PATCH 49/97] callers of iov_copy_from_user_atomic() don't need pagecache

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Date:	Thu, 28 Aug 2014 19:34:57 +0100
From:	Mel Gorman <mgorman@...e.de>
To:	Jiri Slaby <jslaby@...e.cz>
Cc:	Linux-Stable <stable@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>, Mel Gorman <mgorman@...e.de>
Subject: [PATCH 49/97] callers of iov_copy_from_user_atomic() don't need pagecache_disable()

From: Al Viro <viro@...iv.linux.org.uk>

commit 9e8c2af96e0d2d5fe298dd796fb6bc16e888a48d upstream.

... it does that itself (via kmap_atomic())

Signed-off-by: Al Viro <viro@...iv.linux.org.uk>
Signed-off-by: Mel Gorman <mgorman@...e.de>
---
 fs/btrfs/file.c | 5 -----
 fs/fuse/file.c  | 2 --
 mm/filemap.c    | 3 ---
 3 files changed, 10 deletions(-)

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 72da4df..9952a2a 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -426,13 +426,8 @@ static noinline int btrfs_copy_from_user(loff_t pos, int num_pages,
 		struct page *page = prepared_pages[pg];
 		/*
 		 * Copy data from userspace to the current page
-		 *
-		 * Disable pagefault to avoid recursive lock since
-		 * the pages are already locked
 		 */
-		pagefault_disable();
 		copied = iov_iter_copy_from_user_atomic(page, i, offset, count);
-		pagefault_enable();
 
 		/* Flush processor's dcache for this page */
 		flush_dcache_page(page);
diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 4598345..bf9a755 100644
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -985,9 +985,7 @@ static ssize_t fuse_fill_write_pages(struct fuse_req *req,
 		if (mapping_writably_mapped(mapping))
 			flush_dcache_page(page);
 
-		pagefault_disable();
 		tmp = iov_iter_copy_from_user_atomic(page, ii, offset, bytes);
-		pagefault_enable();
 		flush_dcache_page(page);
 
 		mark_page_accessed(page);
diff --git a/mm/filemap.c b/mm/filemap.c
index d0f765f..8144c27 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2190,7 +2190,6 @@ size_t iov_iter_copy_from_user_atomic(struct page *page,
 	char *kaddr;
 	size_t copied;
 
-	BUG_ON(!in_atomic());
 	kaddr = kmap_atomic(page);
 	if (likely(i->nr_segs == 1)) {
 		int left;
@@ -2564,9 +2563,7 @@ again:
 		if (mapping_writably_mapped(mapping))
 			flush_dcache_page(page);
 
-		pagefault_disable();
 		copied = iov_iter_copy_from_user_atomic(page, i, offset, bytes);
-		pagefault_enable();
 		flush_dcache_page(page);
 
 		mark_page_accessed(page);
-- 
1.8.4.5

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