ext4: Properly update i_disksize.

With delayed allocation we use i_data_sem to update i_disksize.  We need
to update i_disksize only if the new size specified is greater than the
current value and we need to make sure we don't race with other
i_disksize update.  With delayed allocation we will switch to the
write_begin function for non-delayed allocation if we are low on free
blocks.  This means the write_begin function for non-delayed allocation
also needs to use the same locking.

We also need to check and update i_disksize even if the new size is less
that inode.i_size because of delayed allocation.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 11 insertions, 0 deletions

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index e13b9deee86..3e47b99a763 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1218,6 +1218,17 @@ do {								\
 #define EXT4_FREEBLOCKS_WATERMARK 0
 #endif
 
+static inline void ext4_update_i_disksize(struct inode *inode, loff_t newsize)
+{
+        /*
+         * XXX: replace with spinlock if seen contended -bzzz
+         */
+        down_write(&EXT4_I(inode)->i_data_sem);
+        if (newsize > EXT4_I(inode)->i_disksize)
+                EXT4_I(inode)->i_disksize = newsize;
+        up_write(&EXT4_I(inode)->i_data_sem);
+        return ;
+}
 
 /*
  * Inodes and files operations