diff mbox

[1/9] fs: add fcntl() interface for setting/getting write life time hints

Message ID 20170627144255.GB2541@infradead.org (mailing list archive)
State New, archived
Headers show

Commit Message

Christoph Hellwig June 27, 2017, 2:42 p.m. UTC 
The API looks ok, but the code could use some cleanups.  What do
you think about the incremental patch below:

It refactors various manipulations, and stores the write hint right
in the iocb as there is a 4 byte hole (this will need some minor
adjustments in the next patches):

Comments

Christoph Hellwig June 27, 2017, 2:52 p.m. UTC | #1 
On Tue, Jun 27, 2017 at 07:42:55AM -0700, Christoph Hellwig wrote:
> The API looks ok, but the code could use some cleanups.  What do
> you think about the incremental patch below:
> 
> It refactors various manipulations, and stores the write hint right
> in the iocb as there is a 4 byte hole (this will need some minor
> adjustments in the next patches):

And looking over the followons I'd love to just store the hints
directly in the inode, bio and request themselves.  We have big
enough holes at least in the bio and request to store them, although
instead of the enum which is at least in sized we'd have to make them
an explicit u16 or even u8.
Jens Axboe June 27, 2017, 2:55 p.m. UTC | #2 
On 06/27/2017 08:42 AM, Christoph Hellwig wrote:
> The API looks ok, but the code could use some cleanups.  What do
> you think about the incremental patch below:
> 
> It refactors various manipulations, and stores the write hint right
> in the iocb as there is a 4 byte hole (this will need some minor
> adjustments in the next patches):

Sigh... Sure, that's how I did it originally as well.

BTW, that patch does not look like an incremental patch, what's
this against?
Christoph Hellwig June 27, 2017, 2:57 p.m. UTC | #3 
On Tue, Jun 27, 2017 at 08:55:02AM -0600, Jens Axboe wrote:
> BTW, that patch does not look like an incremental patch, what's
> this against?

The patch I'm replying to, without the other ones.
Jens Axboe June 27, 2017, 2:58 p.m. UTC | #4 
On 06/27/2017 08:57 AM, Christoph Hellwig wrote:
> On Tue, Jun 27, 2017 at 08:55:02AM -0600, Jens Axboe wrote:
>> BTW, that patch does not look like an incremental patch, what's
>> this against?
> 
> The patch I'm replying to, without the other ones.

Looks like a replacement patch, not incremental to that. I'll
update. And I'm fine with not using flags, in fact that's what
I preferred to do initially.
diff mbox

Patch

diff --git a/fs/fcntl.c b/fs/fcntl.c
index f4e7267d117f..c436278154b4 100644
--- a/fs/fcntl.c
+++ b/fs/fcntl.c
@@ -243,6 +243,63 @@  static int f_getowner_uids(struct file *filp, unsigned long arg)
 }
 #endif
 
+static bool rw_hint_valid(enum rw_hint hint)
+{
+	switch (hint) {
+	case RWF_WRITE_LIFE_NOT_SET:
+	case RWH_WRITE_LIFE_NONE:
+	case RWH_WRITE_LIFE_SHORT:
+	case RWH_WRITE_LIFE_MEDIUM:
+	case RWH_WRITE_LIFE_LONG:
+	case RWH_WRITE_LIFE_EXTREME:
+		return true;
+	default:
+		return false;
+	}
+}
+
+static long fcntl_rw_hint(struct file *file, unsigned int cmd,
+			  unsigned long arg)
+{
+	struct inode *inode = file_inode(file);
+	u64 *argp = (u64 __user *)arg;
+	enum rw_hint hint;
+
+	switch (cmd) {
+	case F_GET_FILE_RW_HINT:
+		if (put_user(__file_write_hint(file), argp))
+			return -EFAULT;
+		return 0;
+	case F_SET_FILE_RW_HINT:
+		if (get_user(hint, argp))
+			return -EFAULT;
+		if (!rw_hint_valid(hint))
+			return -EINVAL;
+
+		spin_lock(&file->f_lock);
+		file->f_write_hint = hint;
+		spin_unlock(&file->f_lock);
+		return 0;
+	case F_GET_RW_HINT:
+		if (put_user(__inode_write_hint(inode), argp))
+			return -EFAULT;
+		return 0;
+	case F_SET_RW_HINT:
+		if (get_user(hint, argp))
+			return -EFAULT;
+		if (!rw_hint_valid(hint))
+			return -EINVAL;
+
+		inode_lock(inode);
+		inode_set_flags(inode, hint << S_WRITE_LIFE_SHIFT,
+				S_WRITE_LIFE_MASK);
+		inode_unlock(inode);
+		return 0;
+	default:
+		return -EINVAL;
+	}
+}
+
 static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
 		struct file *filp)
 {
@@ -337,6 +394,12 @@  static long do_fcntl(int fd, unsigned int cmd, unsigned long arg,
 	case F_GET_SEALS:
 		err = shmem_fcntl(filp, cmd, arg);
 		break;
+	case F_GET_RW_HINT:
+	case F_SET_RW_HINT:
+	case F_GET_FILE_RW_HINT:
+	case F_SET_FILE_RW_HINT:
+		err = fcntl_rw_hint(filp, cmd, arg);
+		break;
 	default:
 		break;
 	}
diff --git a/fs/open.c b/fs/open.c
index cd0c5be8d012..3fe0c4aa7d27 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -759,6 +759,7 @@  static int do_dentry_open(struct file *f,
 	     likely(f->f_op->write || f->f_op->write_iter))
 		f->f_mode |= FMODE_CAN_WRITE;
 
+	f->f_write_hint = WRITE_LIFE_NOT_SET;
 	f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
 
 	file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 4574121f4746..a07e9ce970d1 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -265,6 +265,18 @@  struct page;
 struct address_space;
 struct writeback_control;
 
+/*
+ * Write life time hint values.
+ */
+enum rw_hint {
+	WRITE_LIFE_NOT_SET	= 0,
+	WRITE_LIFE_NONE		= RWH_WRITE_LIFE_NONE,
+	WRITE_LIFE_SHORT	= RWH_WRITE_LIFE_SHORT,
+	WRITE_LIFE_MEDIUM	= RWH_WRITE_LIFE_MEDIUM,
+	WRITE_LIFE_LONG		= RWH_WRITE_LIFE_LONG,
+	WRITE_LIFE_EXTREME	= RWH_WRITE_LIFE_EXTREME,
+};
+
 #define IOCB_EVENTFD		(1 << 0)
 #define IOCB_APPEND		(1 << 1)
 #define IOCB_DIRECT		(1 << 2)
@@ -280,6 +292,7 @@  struct kiocb {
 	void (*ki_complete)(struct kiocb *iocb, long ret, long ret2);
 	void			*private;
 	int			ki_flags;
+	enum rw_hint		ki_hint;
 };
 
 static inline bool is_sync_kiocb(struct kiocb *kiocb)
@@ -851,6 +864,7 @@  struct file {
 	 * Must not be taken from IRQ context.
 	 */
 	spinlock_t		f_lock;
+	enum rw_hint		f_write_hint;
 	atomic_long_t		f_count;
 	unsigned int 		f_flags;
 	fmode_t			f_mode;
@@ -1833,6 +1847,14 @@  struct super_operations {
 #endif
 
 /*
+ * Expected life time hint of a write for this inode. This uses the
+ * WRITE_LIFE_* encoding, we just need to define the shift. We need
+ * 3 bits for this. Next S_* value is 131072, bit 17.
+ */
+#define S_WRITE_LIFE_SHIFT	14	/* 16384, next bit */
+#define S_WRITE_LIFE_MASK	(7 << S_WRITE_LIFE_SHIFT)
+
+/*
  * Note that nosuid etc flags are inode-specific: setting some file-system
  * flags just means all the inodes inherit those flags by default. It might be
  * possible to override it selectively if you really wanted to with some
@@ -1878,6 +1900,35 @@  static inline bool HAS_UNMAPPED_ID(struct inode *inode)
 	return !uid_valid(inode->i_uid) || !gid_valid(inode->i_gid);
 }
 
+static inline enum rw_hint __inode_write_hint(struct inode *inode)
+{
+	return (inode->i_flags >> S_WRITE_LIFE_SHIFT) & 0x7;
+}
+
+static inline enum rw_hint inode_write_hint(struct inode *inode)
+{
+	enum rw_hint ret = __inode_write_hint(inode);
+	if (ret != WRITE_LIFE_NOT_SET)
+		return ret;
+	return WRITE_LIFE_NONE;
+}
+
+static inline enum rw_hint __file_write_hint(struct file *file)
+{
+	if (file->f_write_hint != WRITE_LIFE_NOT_SET)
+		return file->f_write_hint;
+
+	return __inode_write_hint(file_inode(file));
+}
+
+static inline enum rw_hint file_write_hint(struct file *file)
+{
+	enum rw_hint ret = __file_write_hint(file);
+	if (ret != WRITE_LIFE_NOT_SET)
+		return ret;
+	return WRITE_LIFE_NONE;
+}
+
 /*
  * Inode state bits.  Protected by inode->i_lock
  *
diff --git a/include/uapi/linux/fcntl.h b/include/uapi/linux/fcntl.h
index 813afd6eee71..ec69d55bcec7 100644
--- a/include/uapi/linux/fcntl.h
+++ b/include/uapi/linux/fcntl.h
@@ -43,6 +43,27 @@ 
 /* (1U << 31) is reserved for signed error codes */
 
 /*
+ * Set/Get write life time hints. {GET,SET}_RW_HINT operate on the
+ * underlying inode, while {GET,SET}_FILE_RW_HINT operate only on
+ * the specific file.
+ */
+#define F_GET_RW_HINT		(F_LINUX_SPECIFIC_BASE + 11)
+#define F_SET_RW_HINT		(F_LINUX_SPECIFIC_BASE + 12)
+#define F_GET_FILE_RW_HINT	(F_LINUX_SPECIFIC_BASE + 13)
+#define F_SET_FILE_RW_HINT	(F_LINUX_SPECIFIC_BASE + 14)
+
+/*
+ * Valid hint values for F_{GET,SET}_RW_HINT. 0 is "not set", or can be
+ * used to clear any hints previously set.
+ */
+#define RWF_WRITE_LIFE_NOT_SET	0
+#define RWH_WRITE_LIFE_NONE	1
+#define RWH_WRITE_LIFE_SHORT	2
+#define RWH_WRITE_LIFE_MEDIUM	3
+#define RWH_WRITE_LIFE_LONG	4
+#define RWH_WRITE_LIFE_EXTREME	5
+
+/*
  * Types of directory notifications that may be requested.
  */
 #define DN_ACCESS	0x00000001	/* File accessed */