ext4: Take read lock during overwrite case.
When we are overwriting a file and not actually allocating new file system
blocks we need to take only the read lock on i_data_sem.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index a7eb8bb..89cd353 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -901,11 +901,31 @@
int create, int extend_disksize)
{
int retval;
- if (create) {
- down_write((&EXT4_I(inode)->i_data_sem));
+ /*
+ * Try to see if we can get the block without requesting
+ * for new file system block.
+ */
+ down_read((&EXT4_I(inode)->i_data_sem));
+ if (EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL) {
+ retval = ext4_ext_get_blocks(handle, inode, block, max_blocks,
+ bh, 0, 0);
} else {
- down_read((&EXT4_I(inode)->i_data_sem));
+ retval = ext4_get_blocks_handle(handle,
+ inode, block, max_blocks, bh, 0, 0);
}
+ up_read((&EXT4_I(inode)->i_data_sem));
+ if (!create || (retval > 0))
+ return retval;
+
+ /*
+ * We need to allocate new blocks which will result
+ * in i_data update
+ */
+ down_write((&EXT4_I(inode)->i_data_sem));
+ /*
+ * We need to check for EXT4 here because migrate
+ * could have changed the inode type in between
+ */
if (EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL) {
retval = ext4_ext_get_blocks(handle, inode, block, max_blocks,
bh, create, extend_disksize);
@@ -913,11 +933,7 @@
retval = ext4_get_blocks_handle(handle, inode, block,
max_blocks, bh, create, extend_disksize);
}
- if (create) {
- up_write((&EXT4_I(inode)->i_data_sem));
- } else {
- up_read((&EXT4_I(inode)->i_data_sem));
- }
+ up_write((&EXT4_I(inode)->i_data_sem));
return retval;
}