diff mbox

[04/11] fs: add support for allowing applications to pass in write life time hints

Message ID 1497467134-6323-5-git-send-email-axboe@kernel.dk (mailing list archive)
State New, archived
Headers show

Commit Message

Jens Axboe June 14, 2017, 7:05 p.m. UTC 
Add four flags for the pwritev2(2) system call, allowing an application
to give the kernel a hint about what on-media life times can be
expected from a given write.

The intent is for these values to be relative to each other, no
absolute meaning should be attached to these flag names.

Define IOCB flags to carry this information over, and finally
transform them into the block defined stream values.

Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 fs/read_write.c         |  9 ++++++++-
 include/linux/fs.h      | 12 ++++++++++++
 include/uapi/linux/fs.h | 10 ++++++++++
 3 files changed, 30 insertions(+), 1 deletion(-)

Comments

Christoph Hellwig June 14, 2017, 8:26 p.m. UTC | #1 
On Wed, Jun 14, 2017 at 01:05:27PM -0600, Jens Axboe wrote:
> Add four flags for the pwritev2(2) system call, allowing an application
> to give the kernel a hint about what on-media life times can be
> expected from a given write.
> 
> The intent is for these values to be relative to each other, no
> absolute meaning should be attached to these flag names.
> 
> Define IOCB flags to carry this information over, and finally
> transform them into the block defined stream values.

Note that we also have the RWF_NOWAIT flag pending, with which this
would clash.  Maybe move it to the end of the space.
Jens Axboe June 14, 2017, 8:37 p.m. UTC | #2 
On 06/14/2017 02:26 PM, Christoph Hellwig wrote:
> On Wed, Jun 14, 2017 at 01:05:27PM -0600, Jens Axboe wrote:
>> Add four flags for the pwritev2(2) system call, allowing an application
>> to give the kernel a hint about what on-media life times can be
>> expected from a given write.
>>
>> The intent is for these values to be relative to each other, no
>> absolute meaning should be attached to these flag names.
>>
>> Define IOCB flags to carry this information over, and finally
>> transform them into the block defined stream values.
> 
> Note that we also have the RWF_NOWAIT flag pending, with which this
> would clash.  Maybe move it to the end of the space.

That's a trivial thing to resolve. Whomever goes last can resolve
that. I can put them at the end if you feel strongly about it, I
personally don't really care.
diff mbox

Patch

diff --git a/fs/read_write.c b/fs/read_write.c
index 47c1d4484df9..a9b0c3125e0f 100644
--- a/fs/read_write.c
+++ b/fs/read_write.c
@@ -678,7 +678,7 @@  static ssize_t do_iter_readv_writev(struct file *filp, struct iov_iter *iter,
 	struct kiocb kiocb;
 	ssize_t ret;
 
-	if (flags & ~(RWF_HIPRI | RWF_DSYNC | RWF_SYNC))
+	if (flags & ~(RWF_HIPRI | RWF_DSYNC | RWF_SYNC | RWF_WRITE_LIFE_MASK))
 		return -EOPNOTSUPP;
 
 	init_sync_kiocb(&kiocb, filp);
@@ -688,6 +688,13 @@  static ssize_t do_iter_readv_writev(struct file *filp, struct iov_iter *iter,
 		kiocb.ki_flags |= IOCB_DSYNC;
 	if (flags & RWF_SYNC)
 		kiocb.ki_flags |= (IOCB_DSYNC | IOCB_SYNC);
+	if (flags & RWF_WRITE_LIFE_MASK) {
+		struct inode *inode = file_inode(filp);
+
+		inode->i_stream = (flags & RWF_WRITE_LIFE_MASK) >>
+					RWF_WRITE_LIFE_SHIFT;
+		kiocb.ki_flags |= inode->i_stream << IOCB_WRITE_LIFE_SHIFT;
+	}
 	kiocb.ki_pos = *ppos;
 
 	if (type == READ)
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 771e172d23d7..751a1046e87b 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -269,6 +269,12 @@  struct writeback_control;
 #define IOCB_SYNC		(1 << 5)
 #define IOCB_WRITE		(1 << 6)
 
+/*
+ * Steal 4-bits for stream information, this allows 16 valid streams
+ */
+#define IOCB_WRITE_LIFE_SHIFT	7
+#define IOCB_WRITE_LIFE_MASK	(BIT(7) | BIT(8) | BIT(9) | BIT(10))
+
 struct kiocb {
 	struct file		*ki_filp;
 	loff_t			ki_pos;
@@ -292,6 +298,12 @@  static inline void init_sync_kiocb(struct kiocb *kiocb, struct file *filp)
 	};
 }
 
+static inline int iocb_streamid(const struct kiocb *iocb)
+{
+	return (iocb->ki_flags & IOCB_WRITE_LIFE_MASK) >>
+			IOCB_WRITE_LIFE_SHIFT;
+}
+
 /*
  * "descriptor" for what we're up to with a read.
  * This allows us to use the same read code yet
diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
index 24e61a54feaa..58b7ee06b380 100644
--- a/include/uapi/linux/fs.h
+++ b/include/uapi/linux/fs.h
@@ -361,4 +361,14 @@  struct fscrypt_key {
 #define RWF_DSYNC			0x00000002 /* per-IO O_DSYNC */
 #define RWF_SYNC			0x00000004 /* per-IO O_SYNC */
 
+/*
+ * Data life time write flags, steal 4 bits for that
+ */
+#define RWF_WRITE_LIFE_SHIFT		4
+#define RWF_WRITE_LIFE_MASK		0x000000f0 /* 4 bits of stream ID */
+#define RWF_WRITE_LIFE_SHORT		(1 << RWF_WRITE_LIFE_SHIFT)
+#define RWF_WRITE_LIFE_MEDIUM		(2 << RWF_WRITE_LIFE_SHIFT)
+#define RWF_WRITE_LIFE_LONG		(3 << RWF_WRITE_LIFE_SHIFT)
+#define RWF_WRITE_LIFE_EXTREME		(4 << RWF_WRITE_LIFE_SHIFT)
+
 #endif /* _UAPI_LINUX_FS_H */