ext4: make ext4_ext_get_blocks always return <= max_blocks
ext4_ext_get_blocks() returns number of blocks allocated with buffer
heads unmapped for a read from prealloc space. This is needed so that
delayed allocation doesn't do block reservation for prealloc space since
the blocks are already resevred on disk. Fix ext4_ext_get_blocks to not
return greater than max_blocks, since some of the code paths cannot
handle such a return value.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index c2b004e..f4ef0b7 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -2570,8 +2570,18 @@
}
if (create == EXT4_CREATE_UNINITIALIZED_EXT)
goto out;
- if (!create)
+ if (!create) {
+ /*
+ * We have blocks reserved already. We
+ * return allocated blocks so that delalloc
+ * won't do block reservation for us. But
+ * the buffer head will be unmapped so that
+ * a read from the block returns 0s.
+ */
+ if (allocated > max_blocks)
+ allocated = max_blocks;
goto out2;
+ }
ret = ext4_ext_convert_to_initialized(handle, inode,
path, iblock,