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: Christoph Hellwig <hch@xxxxxx>
---
include/linux/blk_types.h | 38 ++++++++++++++++++++++++++++++--------
include/linux/fs.h | 5 -----
2 files changed, 30 insertions(+), 13 deletions(-)
diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index dca972d..70d0ef1 100644
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -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 not
+ * 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);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 16d2b6e..e3e878f 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -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
*/
--
2.1.4
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