linux-kernel - [PATCH 3.14 105/122] callers of iov_copy_from_user_atomic() dont need pagecache

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Date:	Wed, 19 Nov 2014 12:52:35 -0800
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Al Viro <viro@...iv.linux.org.uk>,
	Mel Gorman <mgorman@...e.de>
Subject: [PATCH 3.14 105/122] callers of iov_copy_from_user_atomic() dont need pagecache_disable()

3.14-stable review patch.  If anyone has any objections, please let me know.

------------------

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 fs/btrfs/file.c |    5 -----
 fs/fuse/file.c  |    2 --
 mm/filemap.c    |    3 ---
 3 files changed, 10 deletions(-)

--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -425,13 +425,8 @@ static noinline int btrfs_copy_from_user
 		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);
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1003,9 +1003,7 @@ static ssize_t fuse_fill_write_pages(str
 		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);
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2188,7 +2188,6 @@ size_t iov_iter_copy_from_user_atomic(st
 	char *kaddr;
 	size_t copied;
 
-	BUG_ON(!in_atomic());
 	kaddr = kmap_atomic(page);
 	if (likely(i->nr_segs == 1)) {
 		int left;
@@ -2562,9 +2561,7 @@ 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);


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