netfs: zero the tail of a short DIO/unbuffered readgrafted

The buffered read collector zero-fills the tail of a short read that
stops below the inode's i_size (netfs_clear_unread()), so a read that
races an extending write still returns the expected number of bytes.
The non-buffered collector path does no such thing: it just records
how much was transferred.

Add the same zero-fill for the non-buffered case, gated on
NETFS_SREQ_CLEAR_TAIL: a subreq's source sets that flag when a short
result from it is known to be safe to treat as a hole, as opposed to
NETFS_SREQ_HIT_EOF, which means the read genuinely ran off the end of
the file and should be reported short as-is. Only CLEAR_TAIL should
zero-fill here; a real EOF must stay a real short read.

No source currently sets CLEAR_TAIL on an unbuffered/DIO subrequest,
so this is inert on its own -- a following change teaches cifs to set
it in the one case that needs it.

Fixes: e2d46f2ec332 ("netfs: Change the read result collector to only use one work item")
Reviewed-by: David Howells <dhowells@redhat.com>
Reviewed-by: Namjae Jeon <linkinjeon@kernel.org>
Signed-off-by: Paulo Alcantara <pc@manguebit.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ronnie Sahlberg <ronniesahlberg@gmail.com>
Cc: Shyam Prasad N <sprasad@microsoft.com>
Cc: Tom Talpey <tom@talpey.com>
Cc: Bharath SM <bharathsm@microsoft.com>
Cc: stable@vger.kernel.org

1 files changed, 36 insertions, 0 deletions

diff --git a/block/partitions/atari.h b/block/partitions/atari.h
new file mode 100644
index 000000000..678202442
--- /dev/null
+++ b/block/partitions/atari.h
@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ *  fs/partitions/atari.h
+ *  Moved by Russell King from:
+ *
+ * linux/include/linux/atari_rootsec.h
+ * definitions for Atari Rootsector layout
+ * by Andreas Schwab (schwab@ls5.informatik.uni-dortmund.de)
+ *
+ * modified for ICD/Supra partitioning scheme restricted to at most 12
+ * partitions
+ * by Guenther Kelleter (guenther@pool.informatik.rwth-aachen.de)
+ */
+
+#include <linux/compiler.h>
+
+struct partition_info
+{
+  u8 flg;			/* bit 0: active; bit 7: bootable */
+  char id[3];			/* "GEM", "BGM", "XGM", or other */
+  __be32 st;			/* start of partition */
+  __be32 siz;			/* length of partition */
+};
+
+struct rootsector
+{
+  char unused[0x156];		/* room for boot code */
+  struct partition_info icdpart[8];	/* info for ICD-partitions 5..12 */
+  char unused2[0xc];
+  u32 hd_siz;			/* size of disk in blocks */
+  struct partition_info part[4];
+  u32 bsl_st;			/* start of bad sector list */
+  u32 bsl_cnt;			/* length of bad sector list */
+  u16 checksum;			/* checksum for bootable disks */
+} __packed;
+