From: Chris Mason <chris.mason@oracle.com>
Date: Wed, 7 Jan 2009 14:48:51 +0000 (-0500)
Subject: Btrfs: kmap_atomic(KM_USER0) is safe for btrfs_readpage_end_io_hook
X-Git-Tag: v2.6.29-rc1~27^2~3
X-Git-Url: http://pilppa.com/gitweb/?a=commitdiff_plain;h=9ab86c8e01c3f298dba0cbf2502c635b7f6fc6f9;p=linux-2.6-omap-h63xx.git

Btrfs: kmap_atomic(KM_USER0) is safe for btrfs_readpage_end_io_hook

None of the checksum verification code schedules, so we can use the faster
kmap_atomic

Signed-off-by: Chris Mason <chris.mason@oracle.com>
---

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index cdb701165a0..8adfe059ab4 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1748,7 +1748,7 @@ static int btrfs_readpage_end_io_hook(struct page *page, u64 start, u64 end,
 	} else {
 		ret = get_state_private(io_tree, start, &private);
 	}
-	kaddr = kmap(page);
+	kaddr = kmap_atomic(page, KM_USER0);
 	if (ret)
 		goto zeroit;
 
@@ -1757,7 +1757,7 @@ static int btrfs_readpage_end_io_hook(struct page *page, u64 start, u64 end,
 	if (csum != private)
 		goto zeroit;
 
-	kunmap(page);
+	kunmap_atomic(kaddr, KM_USER0);
 good:
 	/* if the io failure tree for this inode is non-empty,
 	 * check to see if we've recovered from a failed IO
@@ -1772,7 +1772,7 @@ zeroit:
 	       (unsigned long long)private);
 	memset(kaddr + offset, 1, end - start + 1);
 	flush_dcache_page(page);
-	kunmap(page);
+	kunmap_atomic(kaddr, KM_USER0);
 	if (private == 0)
 		return 0;
 	return -EIO;