From: Adam Manzanares <[email protected]>
This is the per-I/O equivalent of the ioprio_set system call.
See the following link for performance implications on a SATA HDD:
https://lkml.org/lkml/2016/12/6/495
First patch factors ioprio_check_cap function out of ioprio_set system call to
also be used by the aio ioprio interface.
Second patch converts kiocb ki_hint field to a u16 to avoid kiocb bloat.
Third patch passes ioprio hint from aio iocb to kiocb and initializes kiocb
ioprio value appropriately when it is not explicitly set.
Fourth patch enables the feature for blkdev.
Fifth patch enables the feature for iomap direct IO
Note: this work is based on top of linux-vfs/for-next
v2: merge patches
use IOCB_FLAG_IOPRIO
validate intended use with IOCB_IOPRIO
add linux-api and linux-block to cc
v3: add ioprio_check_cap function
convert kiocb ki_hint to u16
use ioprio_check_cap when adding ioprio to kiocb in aio.c
v4: handle IOCB_IOPRIO in aio_prep_rw
note patch 3 depends on patch 1 in commit msg
v5: rename ki_hint_valid -> ki_hint_validate
remove ki_hint_validate comment and whitespace
remove IOCB_IOPRIO flag
initialize kiocb to have no priority
v6: add __blkdev_direct_IO_simple ioprio support
Adam Manzanares (5):
block: add ioprio_check_cap function
fs: Convert kiocb rw_hint from enum to u16
fs: Add aio iopriority support
fs: blkdev set bio prio from kiocb prio
fs: iomap dio set bio prio from kiocb prio
block/ioprio.c | 22 ++++++++++++++++------
drivers/block/loop.c | 3 +++
fs/aio.c | 16 ++++++++++++++++
fs/block_dev.c | 2 ++
fs/iomap.c | 1 +
include/linux/fs.h | 16 ++++++++++++++--
include/linux/ioprio.h | 2 ++
include/uapi/linux/aio_abi.h | 1 +
8 files changed, 55 insertions(+), 8 deletions(-)
--
2.15.1
From: Adam Manzanares <[email protected]>
In order to avoid kiocb bloat for per command iopriority support, rw_hint
is converted from enum to a u16. Added a guard around ki_hint assignment.
Signed-off-by: Adam Manzanares <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
---
include/linux/fs.h | 13 +++++++++++--
1 file changed, 11 insertions(+), 2 deletions(-)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 7f07977bdfd7..50de40dbbb85 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -284,6 +284,8 @@ enum rw_hint {
WRITE_LIFE_EXTREME = RWH_WRITE_LIFE_EXTREME,
};
+#define MAX_KI_HINT ((1 << 16) - 1) /* ki_hint type is u16 */
+
#define IOCB_EVENTFD (1 << 0)
#define IOCB_APPEND (1 << 1)
#define IOCB_DIRECT (1 << 2)
@@ -299,7 +301,7 @@ struct kiocb {
void (*ki_complete)(struct kiocb *iocb, long ret, long ret2);
void *private;
int ki_flags;
- enum rw_hint ki_hint;
+ u16 ki_hint;
} __randomize_layout;
static inline bool is_sync_kiocb(struct kiocb *kiocb)
@@ -1927,12 +1929,19 @@ static inline enum rw_hint file_write_hint(struct file *file)
static inline int iocb_flags(struct file *file);
+static inline u16 ki_hint_validate(enum rw_hint hint)
+{
+ if (hint > MAX_KI_HINT)
+ return 0;
+ return hint;
+}
+
static inline void init_sync_kiocb(struct kiocb *kiocb, struct file *filp)
{
*kiocb = (struct kiocb) {
.ki_filp = filp,
.ki_flags = iocb_flags(filp),
- .ki_hint = file_write_hint(filp),
+ .ki_hint = ki_hint_validate(file_write_hint(filp)),
};
}
--
2.15.1
From: Adam Manzanares <[email protected]>
Now that kiocb has an ioprio field copy this over to the bio when it is
created from the kiocb during direct IO.
Signed-off-by: Adam Manzanares <[email protected]>
Reviewed-by: Jeff Moyer <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
---
fs/iomap.c | 1 +
1 file changed, 1 insertion(+)
diff --git a/fs/iomap.c b/fs/iomap.c
index afd163586aa0..65aae194aeca 100644
--- a/fs/iomap.c
+++ b/fs/iomap.c
@@ -919,6 +919,7 @@ iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
bio->bi_iter.bi_sector =
(iomap->addr + pos - iomap->offset) >> 9;
bio->bi_write_hint = dio->iocb->ki_hint;
+ bio->bi_ioprio = dio->iocb->ki_ioprio;
bio->bi_private = dio;
bio->bi_end_io = iomap_dio_bio_end_io;
--
2.15.1
From: Adam Manzanares <[email protected]>
Aio per command iopriority support introduces a second interface between
userland and the kernel capable of passing iopriority. The aio interface also
needs the ability to verify that the submitting context has sufficient
privileges to submit IOPRIO_RT commands. This patch creates the
ioprio_check_cap function to be used by the ioprio_set system call and also by
the aio interface.
Signed-off-by: Adam Manzanares <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
Reviewed-by: Jeff Moyer <[email protected]>
---
block/ioprio.c | 22 ++++++++++++++++------
include/linux/ioprio.h | 2 ++
2 files changed, 18 insertions(+), 6 deletions(-)
diff --git a/block/ioprio.c b/block/ioprio.c
index 6f5d0b6625e3..f9821080c92c 100644
--- a/block/ioprio.c
+++ b/block/ioprio.c
@@ -61,15 +61,10 @@ int set_task_ioprio(struct task_struct *task, int ioprio)
}
EXPORT_SYMBOL_GPL(set_task_ioprio);
-SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
+int ioprio_check_cap(int ioprio)
{
int class = IOPRIO_PRIO_CLASS(ioprio);
int data = IOPRIO_PRIO_DATA(ioprio);
- struct task_struct *p, *g;
- struct user_struct *user;
- struct pid *pgrp;
- kuid_t uid;
- int ret;
switch (class) {
case IOPRIO_CLASS_RT:
@@ -92,6 +87,21 @@ SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
return -EINVAL;
}
+ return 0;
+}
+
+SYSCALL_DEFINE3(ioprio_set, int, which, int, who, int, ioprio)
+{
+ struct task_struct *p, *g;
+ struct user_struct *user;
+ struct pid *pgrp;
+ kuid_t uid;
+ int ret;
+
+ ret = ioprio_check_cap(ioprio);
+ if (ret)
+ return ret;
+
ret = -ESRCH;
rcu_read_lock();
switch (which) {
diff --git a/include/linux/ioprio.h b/include/linux/ioprio.h
index 627efac73e6d..4a28cec49ec3 100644
--- a/include/linux/ioprio.h
+++ b/include/linux/ioprio.h
@@ -77,4 +77,6 @@ extern int ioprio_best(unsigned short aprio, unsigned short bprio);
extern int set_task_ioprio(struct task_struct *task, int ioprio);
+extern int ioprio_check_cap(int ioprio);
+
#endif
--
2.15.1
From: Adam Manzanares <[email protected]>
Now that kiocb has an ioprio field copy this over to the bio when it is
created from the kiocb.
Signed-off-by: Adam Manzanares <[email protected]>
---
fs/block_dev.c | 2 ++
1 file changed, 2 insertions(+)
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 7ec920e27065..11ba99e79d2a 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -216,6 +216,7 @@ __blkdev_direct_IO_simple(struct kiocb *iocb, struct iov_iter *iter,
bio.bi_write_hint = iocb->ki_hint;
bio.bi_private = current;
bio.bi_end_io = blkdev_bio_end_io_simple;
+ bio.bi_ioprio = iocb->ki_ioprio;
ret = bio_iov_iter_get_pages(&bio, iter);
if (unlikely(ret))
@@ -355,6 +356,7 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
bio->bi_write_hint = iocb->ki_hint;
bio->bi_private = dio;
bio->bi_end_io = blkdev_bio_end_io;
+ bio->bi_ioprio = iocb->ki_ioprio;
ret = bio_iov_iter_get_pages(bio, iter);
if (unlikely(ret)) {
--
2.15.1
From: Adam Manzanares <[email protected]>
This is the per-I/O equivalent of the ioprio_set system call.
When IOCB_FLAG_IOPRIO is set on the iocb aio_flags field, then we set the
newly added kiocb ki_ioprio field to the value in the iocb aio_reqprio field.
This patch depends on block: add ioprio_check_cap function.
Signed-off-by: Adam Manzanares <[email protected]>
Reviewed-by: Jeff Moyer <[email protected]>
Reviewed-by: Christoph Hellwig <[email protected]>
---
drivers/block/loop.c | 3 +++
fs/aio.c | 16 ++++++++++++++++
include/linux/fs.h | 3 +++
include/uapi/linux/aio_abi.h | 1 +
4 files changed, 23 insertions(+)
diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index 5d4e31655d96..dd98dfd97f5e 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -76,6 +76,8 @@
#include <linux/miscdevice.h>
#include <linux/falloc.h>
#include <linux/uio.h>
+#include <linux/ioprio.h>
+
#include "loop.h"
#include <linux/uaccess.h>
@@ -559,6 +561,7 @@ static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,
cmd->iocb.ki_filp = file;
cmd->iocb.ki_complete = lo_rw_aio_complete;
cmd->iocb.ki_flags = IOCB_DIRECT;
+ cmd->iocb.ki_ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, 0);
if (cmd->css)
kthread_associate_blkcg(cmd->css);
diff --git a/fs/aio.c b/fs/aio.c
index 755d3f57bcc8..8225013f70f0 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1451,6 +1451,22 @@ static int aio_prep_rw(struct kiocb *req, struct iocb *iocb)
if (iocb->aio_flags & IOCB_FLAG_RESFD)
req->ki_flags |= IOCB_EVENTFD;
req->ki_hint = file_write_hint(req->ki_filp);
+ if (iocb->aio_flags & IOCB_FLAG_IOPRIO) {
+ /*
+ * If the IOCB_FLAG_IOPRIO flag of aio_flags is set, then
+ * aio_reqprio is interpreted as an I/O scheduling
+ * class and priority.
+ */
+ ret = ioprio_check_cap(iocb->aio_reqprio);
+ if (ret) {
+ pr_debug("aio ioprio check cap error\n");
+ return -EINVAL;
+ }
+
+ req->ki_ioprio = iocb->aio_reqprio;
+ } else
+ req->ki_ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, 0);
+
ret = kiocb_set_rw_flags(req, iocb->aio_rw_flags);
if (unlikely(ret))
fput(req->ki_filp);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 50de40dbbb85..73b749ed3ea1 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -36,6 +36,7 @@
#include <linux/delayed_call.h>
#include <linux/uuid.h>
#include <linux/errseq.h>
+#include <linux/ioprio.h>
#include <asm/byteorder.h>
#include <uapi/linux/fs.h>
@@ -302,6 +303,7 @@ struct kiocb {
void *private;
int ki_flags;
u16 ki_hint;
+ u16 ki_ioprio; /* See linux/ioprio.h */
} __randomize_layout;
static inline bool is_sync_kiocb(struct kiocb *kiocb)
@@ -1942,6 +1944,7 @@ static inline void init_sync_kiocb(struct kiocb *kiocb, struct file *filp)
.ki_filp = filp,
.ki_flags = iocb_flags(filp),
.ki_hint = ki_hint_validate(file_write_hint(filp)),
+ .ki_ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, 0),
};
}
diff --git a/include/uapi/linux/aio_abi.h b/include/uapi/linux/aio_abi.h
index 2c0a3415beee..d4e768d55d14 100644
--- a/include/uapi/linux/aio_abi.h
+++ b/include/uapi/linux/aio_abi.h
@@ -55,6 +55,7 @@ enum {
* is valid.
*/
#define IOCB_FLAG_RESFD (1 << 0)
+#define IOCB_FLAG_IOPRIO (1 << 1)
/* read() from /dev/aio returns these structures. */
struct io_event {
--
2.15.1
[email protected] writes:
> From: Adam Manzanares <[email protected]>
>
> Now that kiocb has an ioprio field copy this over to the bio when it is
> created from the kiocb.
>
> Signed-off-by: Adam Manzanares <[email protected]>
Reviewed-by: Jeff Moyer <[email protected]>
Thanks!
Jeff
> ---
> fs/block_dev.c | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/fs/block_dev.c b/fs/block_dev.c
> index 7ec920e27065..11ba99e79d2a 100644
> --- a/fs/block_dev.c
> +++ b/fs/block_dev.c
> @@ -216,6 +216,7 @@ __blkdev_direct_IO_simple(struct kiocb *iocb, struct iov_iter *iter,
> bio.bi_write_hint = iocb->ki_hint;
> bio.bi_private = current;
> bio.bi_end_io = blkdev_bio_end_io_simple;
> + bio.bi_ioprio = iocb->ki_ioprio;
>
> ret = bio_iov_iter_get_pages(&bio, iter);
> if (unlikely(ret))
> @@ -355,6 +356,7 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
> bio->bi_write_hint = iocb->ki_hint;
> bio->bi_private = dio;
> bio->bi_end_io = blkdev_bio_end_io;
> + bio->bi_ioprio = iocb->ki_ioprio;
>
> ret = bio_iov_iter_get_pages(bio, iter);
> if (unlikely(ret)) {
On 5/22/18 9:07 AM, [email protected] wrote:
> From: Adam Manzanares <[email protected]>
>
> In order to avoid kiocb bloat for per command iopriority support, rw_hint
> is converted from enum to a u16. Added a guard around ki_hint assignment.
>
> Signed-off-by: Adam Manzanares <[email protected]>
> Reviewed-by: Christoph Hellwig <[email protected]>
> ---
> include/linux/fs.h | 13 +++++++++++--
> 1 file changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 7f07977bdfd7..50de40dbbb85 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -284,6 +284,8 @@ enum rw_hint {
> WRITE_LIFE_EXTREME = RWH_WRITE_LIFE_EXTREME,
> };
>
> +#define MAX_KI_HINT ((1 << 16) - 1) /* ki_hint type is u16 */
Instead of having to do this and now rely on those now being synced,
how about something like the below.
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 760d8da1b6c7..070438d0b62d 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -299,7 +299,7 @@ struct kiocb {
void (*ki_complete)(struct kiocb *iocb, long ret, long ret2);
void *private;
int ki_flags;
- enum rw_hint ki_hint;
+ u16 ki_hint;
} __randomize_layout;
static inline bool is_sync_kiocb(struct kiocb *kiocb)
@@ -1927,12 +1927,22 @@ static inline enum rw_hint file_write_hint(struct file *file)
static inline int iocb_flags(struct file *file);
+static inline u16 ki_hint_validate(enum rw_hint hint)
+{
+ typeof(((struct kiocb *)0)->ki_hint) max_hint = -1;
+
+ if (hint <= max_hint)
+ return hint;
+
+ return 0;
+}
+
static inline void init_sync_kiocb(struct kiocb *kiocb, struct file *filp)
{
*kiocb = (struct kiocb) {
.ki_filp = filp,
.ki_flags = iocb_flags(filp),
- .ki_hint = file_write_hint(filp),
+ .ki_hint = ki_hint_validate(file_write_hint(filp)),
};
}
--
Jens Axboe
On 5/22/18 8:32 AM, Jens Axboe wrote:
> On 5/22/18 9:07 AM, [email protected] wrote:
>> From: Adam Manzanares <[email protected]>
>>
>> In order to avoid kiocb bloat for per command iopriority support, rw_hint
>> is converted from enum to a u16. Added a guard around ki_hint assignment.
>>
>> Signed-off-by: Adam Manzanares <[email protected]>
>> Reviewed-by: Christoph Hellwig <[email protected]>
>> ---
>> include/linux/fs.h | 13 +++++++++++--
>> 1 file changed, 11 insertions(+), 2 deletions(-)
>>
>> diff --git a/include/linux/fs.h b/include/linux/fs.h
>> index 7f07977bdfd7..50de40dbbb85 100644
>> --- a/include/linux/fs.h
>> +++ b/include/linux/fs.h
>> @@ -284,6 +284,8 @@ enum rw_hint {
>> WRITE_LIFE_EXTREME = RWH_WRITE_LIFE_EXTREME,
>> };
>>
>> +#define MAX_KI_HINT ((1 << 16) - 1) /* ki_hint type is u16 */
>
> Instead of having to do this and now rely on those now being synced,
> how about something like the below.
>
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 760d8da1b6c7..070438d0b62d 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -299,7 +299,7 @@ struct kiocb {
> void (*ki_complete)(struct kiocb *iocb, long ret, long ret2);
> void *private;
> int ki_flags;
> - enum rw_hint ki_hint;
> + u16 ki_hint;
> } __randomize_layout;
>
> static inline bool is_sync_kiocb(struct kiocb *kiocb)
> @@ -1927,12 +1927,22 @@ static inline enum rw_hint file_write_hint(struct file *file)
>
> static inline int iocb_flags(struct file *file);
>
> +static inline u16 ki_hint_validate(enum rw_hint hint)
> +{
> + typeof(((struct kiocb *)0)->ki_hint) max_hint = -1;
> +
> + if (hint <= max_hint)
> + return hint;
> +
> + return 0;
> +}
> +
> static inline void init_sync_kiocb(struct kiocb *kiocb, struct file *filp)
> {
> *kiocb = (struct kiocb) {
> .ki_filp = filp,
> .ki_flags = iocb_flags(filp),
> - .ki_hint = file_write_hint(filp),
> + .ki_hint = ki_hint_validate(file_write_hint(filp)),
> };
> }
Looks good. I'll resubmit.
>
>
On 05/22/2018 10:32 AM, Jens Axboe wrote:
> On 5/22/18 9:07 AM, [email protected] wrote:
>> From: Adam Manzanares <[email protected]>
>>
>> In order to avoid kiocb bloat for per command iopriority support, rw_hint
>> is converted from enum to a u16. Added a guard around ki_hint assignment.
>>
>> Signed-off-by: Adam Manzanares <[email protected]>
>> Reviewed-by: Christoph Hellwig <[email protected]>
>> ---
>> include/linux/fs.h | 13 +++++++++++--
>> 1 file changed, 11 insertions(+), 2 deletions(-)
>>
>> diff --git a/include/linux/fs.h b/include/linux/fs.h
>> index 7f07977bdfd7..50de40dbbb85 100644
>> --- a/include/linux/fs.h
>> +++ b/include/linux/fs.h
>> @@ -284,6 +284,8 @@ enum rw_hint {
>> WRITE_LIFE_EXTREME = RWH_WRITE_LIFE_EXTREME,
>> };
>>
>> +#define MAX_KI_HINT ((1 << 16) - 1) /* ki_hint type is u16 */
>
> Instead of having to do this and now rely on those now being synced,
> how about something like the below.
>
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index 760d8da1b6c7..070438d0b62d 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -299,7 +299,7 @@ struct kiocb {
> void (*ki_complete)(struct kiocb *iocb, long ret, long ret2);
> void *private;
> int ki_flags;
> - enum rw_hint ki_hint;
> + u16 ki_hint;
> } __randomize_layout;
>
> static inline bool is_sync_kiocb(struct kiocb *kiocb)
> @@ -1927,12 +1927,22 @@ static inline enum rw_hint file_write_hint(struct file *file)
>
> static inline int iocb_flags(struct file *file);
>
> +static inline u16 ki_hint_validate(enum rw_hint hint)
> +{
> + typeof(((struct kiocb *)0)->ki_hint) max_hint = -1;
This looks complex to me. Would force a reader to lookback at what
datatype ki_hint is. I'd prefer to declare it as u16 max_hint = -1, or
even the previous #define MAX_KI_HINT format is easier to read. Just a
program reading style you are comfortable with though.
--
Goldwyn
On 5/22/18 10:24 AM, Goldwyn Rodrigues wrote:
>
>
> On 05/22/2018 10:32 AM, Jens Axboe wrote:
>> On 5/22/18 9:07 AM, [email protected] wrote:
>>> From: Adam Manzanares <[email protected]>
>>>
>>> In order to avoid kiocb bloat for per command iopriority support, rw_hint
>>> is converted from enum to a u16. Added a guard around ki_hint assignment.
>>>
>>> Signed-off-by: Adam Manzanares <[email protected]>
>>> Reviewed-by: Christoph Hellwig <[email protected]>
>>> ---
>>> include/linux/fs.h | 13 +++++++++++--
>>> 1 file changed, 11 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/include/linux/fs.h b/include/linux/fs.h
>>> index 7f07977bdfd7..50de40dbbb85 100644
>>> --- a/include/linux/fs.h
>>> +++ b/include/linux/fs.h
>>> @@ -284,6 +284,8 @@ enum rw_hint {
>>> WRITE_LIFE_EXTREME = RWH_WRITE_LIFE_EXTREME,
>>> };
>>>
>>> +#define MAX_KI_HINT ((1 << 16) - 1) /* ki_hint type is u16 */
>>
>> Instead of having to do this and now rely on those now being synced,
>> how about something like the below.
>>
>> diff --git a/include/linux/fs.h b/include/linux/fs.h
>> index 760d8da1b6c7..070438d0b62d 100644
>> --- a/include/linux/fs.h
>> +++ b/include/linux/fs.h
>> @@ -299,7 +299,7 @@ struct kiocb {
>> void (*ki_complete)(struct kiocb *iocb, long ret, long ret2);
>> void *private;
>> int ki_flags;
>> - enum rw_hint ki_hint;
>> + u16 ki_hint;
>> } __randomize_layout;
>>
>> static inline bool is_sync_kiocb(struct kiocb *kiocb)
>> @@ -1927,12 +1927,22 @@ static inline enum rw_hint file_write_hint(struct file *file)
>>
>> static inline int iocb_flags(struct file *file);
>>
>> +static inline u16 ki_hint_validate(enum rw_hint hint)
>> +{
>> + typeof(((struct kiocb *)0)->ki_hint) max_hint = -1;
>
> This looks complex to me. Would force a reader to lookback at what
> datatype ki_hint is. I'd prefer to declare it as u16 max_hint = -1, or
> even the previous #define MAX_KI_HINT format is easier to read. Just a
> program reading style you are comfortable with though.
How is it complex? It's defining a type that'll be the same as ki_hint
in the kiocb, which is _exactly_ what we care about. Any sort of other
definition will rely on those two locations now being synced. The
above will never break.
So I strongly disagree. The above will _never_ require the reader to
figure out what the type is. Any other variant will _always_ require
the reader to check if they are the same.
--
Jens Axboe
On 5/22/18 9:30 AM, Jens Axboe wrote:
> On 5/22/18 10:24 AM, Goldwyn Rodrigues wrote:
>>
>>
>> On 05/22/2018 10:32 AM, Jens Axboe wrote:
>>> On 5/22/18 9:07 AM, [email protected] wrote:
>>>> From: Adam Manzanares <[email protected]>
>>>>
>>>> In order to avoid kiocb bloat for per command iopriority support, rw_hint
>>>> is converted from enum to a u16. Added a guard around ki_hint assignment.
>>>>
>>>> Signed-off-by: Adam Manzanares <[email protected]>
>>>> Reviewed-by: Christoph Hellwig <[email protected]>
>>>> ---
>>>> include/linux/fs.h | 13 +++++++++++--
>>>> 1 file changed, 11 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/include/linux/fs.h b/include/linux/fs.h
>>>> index 7f07977bdfd7..50de40dbbb85 100644
>>>> --- a/include/linux/fs.h
>>>> +++ b/include/linux/fs.h
>>>> @@ -284,6 +284,8 @@ enum rw_hint {
>>>> WRITE_LIFE_EXTREME = RWH_WRITE_LIFE_EXTREME,
>>>> };
>>>>
>>>> +#define MAX_KI_HINT ((1 << 16) - 1) /* ki_hint type is u16 */
>>>
>>> Instead of having to do this and now rely on those now being synced,
>>> how about something like the below.
>>>
>>> diff --git a/include/linux/fs.h b/include/linux/fs.h
>>> index 760d8da1b6c7..070438d0b62d 100644
>>> --- a/include/linux/fs.h
>>> +++ b/include/linux/fs.h
>>> @@ -299,7 +299,7 @@ struct kiocb {
>>> void (*ki_complete)(struct kiocb *iocb, long ret, long ret2);
>>> void *private;
>>> int ki_flags;
>>> - enum rw_hint ki_hint;
>>> + u16 ki_hint;
>>> } __randomize_layout;
>>>
>>> static inline bool is_sync_kiocb(struct kiocb *kiocb)
>>> @@ -1927,12 +1927,22 @@ static inline enum rw_hint file_write_hint(struct file *file)
>>>
>>> static inline int iocb_flags(struct file *file);
>>>
>>> +static inline u16 ki_hint_validate(enum rw_hint hint)
>>> +{
>>> + typeof(((struct kiocb *)0)->ki_hint) max_hint = -1;
>>
>> This looks complex to me. Would force a reader to lookback at what
>> datatype ki_hint is. I'd prefer to declare it as u16 max_hint = -1, or
>> even the previous #define MAX_KI_HINT format is easier to read. Just a
>> program reading style you are comfortable with though.
>
> How is it complex? It's defining a type that'll be the same as ki_hint
> in the kiocb, which is _exactly_ what we care about. Any sort of other
> definition will rely on those two locations now being synced. The
> above will never break.
>
> So I strongly disagree. The above will _never_ require the reader to
> figure out what the type is. Any other variant will _always_ require
> the reader to check if they are the same.
>
I do think the previous code was a bit easier to parse at first glance,
but that is outweighed by the fact that the validate function is now
directly tied to the kiocb ki_hint type.
I also missed one spot where I should have used ki_hint_validate. Will
resend soon.