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dm: fix dm_io and dm_target_io flags race condition on Alpha 

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@redhat.com>
Fixes: bd4a6dd241 ("dm: reduce size of dm_io and dm_target_io structs")
[snitzer: Jens allowed this change since Mikulas owns a relevant Alpha!]
Acked-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Mike Snitzer <snitzer@kernel.org>
This commit is contained in:
Mikulas Patocka 2022-03-28 12:34:31 -04:00 committed by Mike Snitzer
parent cc09e8a9de
commit aad5b23ebf
2 changed files with 4 additions and 2 deletions
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4
drivers/md/dm-core.h
View File

@ -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(struct dm_target_io *tio, unsigned int bit)
#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;

2
include/linux/blk_types.h
View File

@ -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)