Btrfs: use i_size_read() in btrfs_defrag_file()

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>

1 files changed, 4 insertions, 3 deletions

diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index b39f7bf92704..323d77f09258 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -978,6 +978,7 @@ 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;
@@ -1003,7 +1004,7 @@ 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;
 
         /*
@@ -1028,10 +1029,10 @@ 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) {