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Commit 87374179 authored by Christoph Hellwig's avatar Christoph Hellwig Committed by Jens Axboe
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block: add a proper block layer data direction encoding 



Currently the block layer op_is_write, bio_data_dir and rq_data_dir
helper treat every operation that is not a READ as a data out operation.
This worked surprisingly long, but the new REQ_OP_ZONE_REPORT operation
actually adds a second operation that reads data from the device.
Surprisingly nothing critical relied on this direction, but this might
be a good opportunity to properly fix this issue up.

We take a little inspiration and use the least significant bit of the
operation number to encode the data direction, which just requires us
to renumber the operations to fix this scheme.

Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
Reviewed-by: default avatarShaun Tancheff <shaun.tancheff@seagate.com>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent ef295ecf

include/linux/blk_types.h

+30 −8
Original line number Diff line number Diff line
@@ -131,20 +131,37 @@ struct bio { 
/*

 * Operations and flags common to the bio and request structures.

 * We use 8 bits for encoding the operation, and the remaining 24 for flags.

 *

 * The least significant bit of the operation number indicates the data

 * transfer direction:

 *

 *   - if the least significant bit is set transfers are TO the device

 *   - if the least significant bit is not set transfers are FROM the device

 *

 * If a operation does not transfer data the least significant bit has no

 * meaning.

 */

#define REQ_OP_BITS	8

#define REQ_OP_MASK	((1 << REQ_OP_BITS) - 1)

#define REQ_FLAG_BITS	24



enum req_opf {

	REQ_OP_READ,

	REQ_OP_WRITE,

	REQ_OP_DISCARD,		/* request to discard sectors */

	REQ_OP_SECURE_ERASE,	/* request to securely erase sectors */

	REQ_OP_WRITE_SAME,	/* write same block many times */

	REQ_OP_FLUSH,		/* request for cache flush */

	REQ_OP_ZONE_REPORT,	/* Get zone information */

	REQ_OP_ZONE_RESET,	/* Reset a zone write pointer */

	/* read sectors from the device */

	REQ_OP_READ		= 0,

	/* write sectors to the device */

	REQ_OP_WRITE		= 1,

	/* flush the volatile write cache */

	REQ_OP_FLUSH		= 2,

	/* discard sectors */

	REQ_OP_DISCARD		= 3,

	/* get zone information */

	REQ_OP_ZONE_REPORT	= 4,

	/* securely erase sectors */

	REQ_OP_SECURE_ERASE	= 5,

	/* seset a zone write pointer */

	REQ_OP_ZONE_RESET	= 6,

	/* write the same sector many times */

	REQ_OP_WRITE_SAME	= 7,



	REQ_OP_LAST,

};
@@ -194,6 +211,11 @@ enum req_flag_bits { 
#define bio_set_op_attrs(bio, op, op_flags) \

	((bio)->bi_opf |= (op | op_flags))



static inline bool op_is_write(unsigned int op)

{

	return (op & 1);

}



static inline bool op_is_sync(unsigned int op)

{

	return (op & REQ_OP_MASK) == REQ_OP_READ || (op & REQ_SYNC);

include/linux/fs.h

+0 −5
Original line number Diff line number Diff line
@@ -2499,11 +2499,6 @@ extern void make_bad_inode(struct inode *); 
extern bool is_bad_inode(struct inode *);



#ifdef CONFIG_BLOCK

static inline bool op_is_write(unsigned int op)

{

	return op == REQ_OP_READ ? false : true;

}



/*

 * return data direction, READ or WRITE

 */