ext4_ext_get_blocks returns number of blocks allocated with buffer head
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 and also mark the buffer head unwritten. Some code path tries
to read the block if buffer_head is not new and no uptodate. Marking the buffer
head unwritten avoid this reading.
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
---
fs/ext4/extents.c | 14 +++++++++++++-
1 files changed, 13 insertions(+), 1 deletions(-)
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index d6ae40a..edd1bf2 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -2600,8 +2600,20 @@ int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
}
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 return 0
+ */
+ if (allocated > max_blocks)
+ allocated = max_blocks;
+ /* mark the buffer unwritten */
+ __set_bit(BH_Unwritten, &bh_result->b_state);
goto out2;
+ }
ret = ext4_ext_convert_to_initialized(handle, inode,
path, iblock,
--
1.5.5.rc0.16.g02b00.dirty
--
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