From: Amir Goldstein <amir73il@xxxxxxxxxxxx>
With indirect mapped files, direct I/O write is not allowed to
initialize holes, so stale data won't be exposed.
With snapshots, direct I/O write is not allowed to do move-on-write,
for the exact same reason.
Signed-off-by: Amir Goldstein <amir73il@xxxxxxxxxxxx>
Signed-off-by: Yongqiang Yang <xiaoqiangnk@xxxxxxxxx>
---
fs/ext4/inode.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++--
1 files changed, 48 insertions(+), 2 deletions(-)
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 2d7e540..1cb94d2 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1373,6 +1373,16 @@ int ext4_map_blocks(handle_t *handle, struct inode *inode,
return ret;
}
+ if (retval > 0 && (map->m_flags & EXT4_MAP_REMAP) &&
+ (flags & EXT4_GET_BLOCKS_PRE_IO)) {
+ /*
+ * If mow is needed on the requested block and
+ * request comes from async-direct-io-write path,
+ * we return an unmapped buffer to fall back to buffered I/O.
+ */
+ map->m_flags &= ~EXT4_MAP_MAPPED;
+ return 0;
+ }
/* If it is only a block(s) look up */
if ((flags & EXT4_GET_BLOCKS_CREATE) == 0)
return retval;
@@ -3654,6 +3664,29 @@ static int ext4_releasepage(struct page *page, gfp_t wait)
}
/*
+ * ext4_get_block_dio used when preparing for a DIO write
+ * to indirect mapped files with snapshots.
+ */
+int ext4_get_block_dio_write(struct inode *inode, sector_t iblock,
+ struct buffer_head *bh, int create)
+{
+ int flags = EXT4_GET_BLOCKS_CREATE;
+
+ /*
+ * DIO_SKIP_HOLES may ask to map direct I/O write with create=0,
+ * but we know this is a write, so we need to check if block
+ * needs to be moved to snapshot and fall back to buffered I/O.
+ * ext4_map_blocks() will return an unmapped buffer if block
+ * is not allocated or if it needs to be moved to snapshot.
+ */
+ if (ext4_snapshot_should_move_data(inode))
+ flags |= EXT4_GET_BLOCKS_MOVE_ON_WRITE|
+ EXT4_GET_BLOCKS_PRE_IO;
+
+ return _ext4_get_block(inode, iblock, bh, flags);
+}
+
+/*
* O_DIRECT for ext3 (or indirect map) based files
*
* If the O_DIRECT write will extend the file then add this inode to the
@@ -3708,6 +3741,16 @@ retry:
ret = blockdev_direct_IO(rw, iocb, inode,
inode->i_sb->s_bdev, iov,
offset, nr_segs,
+ /*
+ * snapshots code gets here for DIO write
+ * to ind mapped files or outside i_size
+ * of extent mapped files and for DIO read
+ * to all files.
+ * XXX: isn't it possible to expose stale data
+ * on DIO read to newly allocated ind map
+ * blocks or newly MOWed blocks?
+ */
+ (rw == WRITE) ? ext4_get_block_dio_write :
ext4_get_block, NULL);
if (unlikely((rw & WRITE) && ret < 0)) {
@@ -3769,10 +3812,13 @@ out:
static int ext4_get_block_write(struct inode *inode, sector_t iblock,
struct buffer_head *bh_result, int create)
{
+ int flags = EXT4_GET_BLOCKS_IO_CREATE_EXT;
+
ext4_debug("ext4_get_block_write: inode %lu, create flag %d\n",
inode->i_ino, create);
- return _ext4_get_block(inode, iblock, bh_result,
- EXT4_GET_BLOCKS_IO_CREATE_EXT);
+ if (ext4_snapshot_should_move_data(inode))
+ flags |= EXT4_GET_BLOCKS_MOVE_ON_WRITE;
+ return _ext4_get_block(inode, iblock, bh_result, flags);
}
static void ext4_end_io_dio(struct kiocb *iocb, loff_t offset,
--
1.7.4.1
--
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