linux-kernel - [PATCH 1/2] LSEEK: BTRFS: Avoid i_mutex for SEEK

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Date:	Sat, 1 Oct 2011 22:49:27 +0200
From:	Andres Freund <andres@...razel.de>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	robertmhaas@...il.com, viro@...iv.linux.org.uk,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] LSEEK: BTRFS: Avoid i_mutex for SEEK_{CUR,SET,END}


Don't need the i_mutex for those cases, only for SEEK_HOLE/DATA.

Really-From: Andi Kleen <ak@...ux.intel.com>
Signed-off-by: Andi Kleen <ak@...ux.intel.com>
Signed-off-by: Andres Freund <andres@...razel.de>
---
 fs/btrfs/file.c |   27 +++++++++++----------------
 1 files changed, 11 insertions(+), 16 deletions(-)

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 7a13337..5bc7116 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1809,24 +1809,19 @@ static loff_t btrfs_file_llseek(struct file *file, loff_t offset, int origin)
 	struct inode *inode = file->f_mapping->host;
 	int ret;
 
+	if (origin != SEEK_DATA && origin != SEEK_HOLE)
+		return generic_file_llseek(file, offset, origin);
+
 	mutex_lock(&inode->i_mutex);
-	switch (origin) {
-	case SEEK_END:
-	case SEEK_CUR:
-		offset = generic_file_llseek(file, offset, origin);
-		goto out;
-	case SEEK_DATA:
-	case SEEK_HOLE:
-		if (offset >= i_size_read(inode)) {
-			mutex_unlock(&inode->i_mutex);
-			return -ENXIO;
-		}
+	if (offset >= i_size_read(inode)) {
+		mutex_unlock(&inode->i_mutex);
+		return -ENXIO;
+	}
 
-		ret = find_desired_extent(inode, &offset, origin);
-		if (ret) {
-			mutex_unlock(&inode->i_mutex);
-			return ret;
-		}
+	ret = find_desired_extent(inode, &offset, origin);
+	if (ret) {
+		mutex_unlock(&inode->i_mutex);
+		return ret;
 	}
 
 	if (offset < 0 && !(file->f_mode & FMODE_UNSIGNED_OFFSET)) {
-- 
1.7.6.409.ge7a85.dirty

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