[PATCH 2/4] Btrfs: use i_size_read() in btrfs_defrag_file()

[Li Zefan <lizf@cn.fujitsu.com>]

Don't use inode->i_size directly, since we're not holding i_mutex.

This also fixes another bug, that i_size can change after it's checked
against 0 and then (i_size - 1) can be negative.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
---
 fs/btrfs/ioctl.c |    7 ++++---
 1 files changed, 4 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 31fe6d4..6f2b257 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -972,6 +972,7 @@ int btrfs_defrag_file(struct inode *inode, struct file *file,
 	struct btrfs_super_block *disk_super;
 	struct file_ra_state *ra = NULL;
 	unsigned long last_index;
+	u64 isize = i_size_read(inode);
 	u64 features;
 	u64 last_len = 0;
 	u64 skip = 0;
@@ -997,7 +998,7 @@ int btrfs_defrag_file(struct inode *inode, struct file *file,
 			compress_type = range->compress_type;
 	}
 
-	if (inode->i_size == 0)
+	if (isize == 0)
 		return 0;
 
 	/*
@@ -1022,10 +1023,10 @@ int btrfs_defrag_file(struct inode *inode, struct file *file,
 
 	/* find the last page to defrag */
 	if (range->start + range->len > range->start) {
-		last_index = min_t(u64, inode->i_size - 1,
+		last_index = min_t(u64, isize - 1,
 			 range->start + range->len - 1) >> PAGE_CACHE_SHIFT;
 	} else {
-		last_index = (inode->i_size - 1) >> PAGE_CACHE_SHIFT;
+		last_index = (isize - 1) >> PAGE_CACHE_SHIFT;
 	}
 
 	if (newer_than) {
-- 
1.7.3.1