Early alpha processors cannot write a single byte or short; they read 8
bytes, modify the value in registers and write back 8 bytes.
This could cause race condition in the structure dm_io - if the fields
flags and io_count are modified simultaneously.
Fix this bug by using 32-bit flags if we are on Alpha and if we are
compiling for a processor that doesn't have the byte-word-extension.
Signed-off-by: Mikulas Patocka <mpatocka@xxxxxxxxxx>
Fixes: bd4a6dd241ae ("dm: reduce size of dm_io and dm_target_io structs")
---
drivers/md/dm-core.h | 4 ++--
include/linux/blk_types.h | 2 ++
2 files changed, 4 insertions(+), 2 deletions(-)
Index: linux-2.6/include/linux/blk_types.h
===================================================================
--- linux-2.6.orig/include/linux/blk_types.h 2022-03-28 18:11:15.000000000 +0200
+++ linux-2.6/include/linux/blk_types.h 2022-03-28 18:20:23.000000000 +0200
@@ -85,8 +85,10 @@ struct block_device {
*/
#if defined(CONFIG_ALPHA) && !defined(__alpha_bwx__)
typedef u32 __bitwise blk_status_t;
+typedef u32 blk_short_t;
#else
typedef u8 __bitwise blk_status_t;
+typedef u16 blk_short_t;
#endif
#define BLK_STS_OK 0
#define BLK_STS_NOTSUPP ((__force blk_status_t)1)
Index: linux-2.6/drivers/md/dm-core.h
===================================================================
--- linux-2.6.orig/drivers/md/dm-core.h 2022-03-28 18:11:11.000000000 +0200
+++ linux-2.6/drivers/md/dm-core.h 2022-03-28 18:21:34.000000000 +0200
@@ -210,7 +210,7 @@ struct dm_table {
#define DM_TIO_MAGIC 28714
struct dm_target_io {
unsigned short magic;
- unsigned short flags;
+ blk_short_t flags;
unsigned int target_bio_nr;
struct dm_io *io;
struct dm_target *ti;
@@ -244,7 +244,7 @@ static inline void dm_tio_set_flag(struc
#define DM_IO_MAGIC 19577
struct dm_io {
unsigned short magic;
- unsigned short flags;
+ blk_short_t flags;
atomic_t io_count;
struct mapped_device *md;
struct bio *orig_bio;
--
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