[03/11] Add support for per-file/inode stream ID

Commit Message

Jens Axboe March 4, 2016, 4:10 p.m. UTC

Writing on flash devices can be much more efficient, if we can
inform the device what kind of data can be grouped together. If
the device is able to group data together with similar lifetimes,
then it can be more efficient in garbage collection. This, in turn,
leads to lower write amplification, which is a win on both device
wear and performance.

Signed-off-by: Jens Axboe <[e-mail]>
---
 fs/inode.c         |  1 +
 fs/open.c          |  1 +
 include/linux/fs.h | 22 ++++++++++++++++++++++
 3 files changed, 24 insertions(+)

Comments

Jens Axboe March 4, 2016, 8:35 p.m. UTC | #1

On 03/04/2016 11:53 AM, Shaun Tancheff wrote:
> What do you think of falling back to i_ino for applications which don't
> make use of setting stream_id yet?
>
> Something like this (or using a crc16 instead of the xor hack)?
>
> static inline unsigned int inode_streamid(struct inode *inode)
> {
> if (inode) {
> if (inode->i_streamid)
> return inode->i_streamid;
> return ((inode->i_ino >> 16) ^ inode->i_ino) & 0xFFFF;
> }
> return 0;
> }

If the device supports a high enough number of concurrently open 
streams, that might work fine. But if the mask ends up being 0x7, then I 
think it'll just introduce randomness into the whole thing.

But it's something that could be experimented with, certainly.

Patch

diff --git a/fs/inode.c b/fs/inode.c
index 69b8b526c194..3e3652a04509 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -147,6 +147,7 @@  int inode_init_always(struct super_block *sb, struct inode *inode)
 	inode->i_blocks = 0;
 	inode->i_bytes = 0;
 	inode->i_generation = 0;
+	inode->i_streamid = 0;
 	inode->i_pipe = NULL;
 	inode->i_bdev = NULL;
 	inode->i_cdev = NULL;
diff --git a/fs/open.c b/fs/open.c
index 55bdc75e2172..38999d86fae0 100644
--- a/fs/open.c
+++ b/fs/open.c
@@ -749,6 +749,7 @@  static int do_dentry_open(struct file *f,
 	f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
 
 	file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);
+	f->f_streamid = 0;
 
 	return 0;
 
diff --git a/include/linux/fs.h b/include/linux/fs.h
index ae681002100a..10599d231b53 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -660,6 +660,7 @@  struct inode {
 #ifdef CONFIG_IMA
 	atomic_t		i_readcount; /* struct files open RO */
 #endif
+	unsigned int		i_streamid;
 	const struct file_operations	*i_fop;	/* former ->i_op->default_file_ops */
 	struct file_lock_context	*i_flctx;
 	struct address_space	i_data;
@@ -681,6 +682,14 @@  struct inode {
 	void			*i_private; /* fs or device private pointer */
 };
 
+static inline unsigned int inode_streamid(struct inode *inode)
+{
+	if (inode)
+		return inode->i_streamid;
+
+	return 0;
+}
+
 static inline int inode_unhashed(struct inode *inode)
 {
 	return hlist_unhashed(&inode->i_hash);
@@ -877,6 +886,7 @@  struct file {
 	 * Must not be taken from IRQ context.
 	 */
 	spinlock_t		f_lock;
+	unsigned int		f_streamid;
 	atomic_long_t		f_count;
 	unsigned int 		f_flags;
 	fmode_t			f_mode;
@@ -908,6 +918,18 @@  struct file_handle {
 	unsigned char f_handle[0];
 };
 
+/*
+ * If the file doesn't have a stream ID set, return the inode stream ID
+ * in case that has been set.
+ */
+static inline unsigned int file_streamid(struct file *f)
+{
+	if (f->f_streamid)
+		return f->f_streamid;
+
+	return inode_streamid(f->f_inode);
+}
+
 static inline struct file *get_file(struct file *f)
 {
 	atomic_long_inc(&f->f_count);