S_HIPRI is a hint that indicates the file (currently only block devices)
is a high priority file. This hint allows direct-io to the block device
to poll for completions if polling is available to the block device.
The motivation for this patch comes from tiered caching solutions. A
user may wish to have low-latency block devices act as a cache for
higher-latency storage media.
With the introduction of block polling, polling could be enabled on a
queue of a block device. The preadv2/pwritev2 sets allowed a user to
specify per-io polling, but removed the ability to poll per-queue.
Instead of having a user modify their software to use preadv2/pwritev2,
this patch allows a user to set S_HIPRI on a block device file to request
all direct-io for this file to be polled.
Signed-off-by: Jon Derrick <jonathan.derrick@xxxxxxxxx>
---
block/ioctl.c | 43 +++++++++++++++++++++++++++++++++++++++++++
fs/block_dev.c | 3 +++
include/linux/fs.h | 2 ++
include/uapi/linux/fs.h | 2 ++
4 files changed, 50 insertions(+)
diff --git a/block/ioctl.c b/block/ioctl.c
index 4ff1f92..1b50fef 100644
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -520,6 +520,45 @@ static int blkdev_bszset(struct block_device *bdev, fmode_t mode,
return ret;
}
+static int blkdev_hipriget(struct block_device *bdev)
+{
+ return !!(bdev->bd_inode->i_flags & S_HIPRI);
+}
+
+static int blkdev_hipriset(struct block_device *bdev, fmode_t mode,
+ int __user *argp)
+{
+ int n;
+
+ if (!capable(CAP_SYS_ADMIN))
+ return -EACCES;
+ if (!argp)
+ return -EINVAL;
+ if (get_user(n, argp))
+ return -EFAULT;
+
+ n = !!n;
+ if (n == blkdev_hipriget(bdev))
+ return 0;
+
+ if (!(mode & FMODE_EXCL)) {
+ bdgrab(bdev);
+ if (blkdev_get(bdev, mode | FMODE_EXCL, &bdev) < 0)
+ return -EBUSY;
+ }
+
+ inode_lock(bdev->bd_inode);
+ if (n)
+ bdev->bd_inode->i_flags |= S_HIPRI;
+ else
+ bdev->bd_inode->i_flags &= ~S_HIPRI;
+ inode_unlock(bdev->bd_inode);
+
+ if (!(mode & FMODE_EXCL))
+ blkdev_put(bdev, mode | FMODE_EXCL);
+ return 0;
+}
+
/*
* always keep this in sync with compat_blkdev_ioctl()
*/
@@ -601,6 +640,10 @@ int blkdev_ioctl(struct block_device *bdev, fmode_t mode, unsigned cmd,
case BLKDAXGET:
return put_int(arg, !!(bdev->bd_inode->i_flags & S_DAX));
break;
+ case BLKHIPRISET:
+ return blkdev_hipriset(bdev, mode, argp);
+ case BLKHIPRIGET:
+ return put_int(arg, blkdev_hipriget(bdev));
case IOC_PR_REGISTER:
return blkdev_pr_register(bdev, argp);
case IOC_PR_RESERVE:
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 252e459..ede8325 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -170,6 +170,9 @@ blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, loff_t offset)
if (IS_DAX(inode))
return dax_do_io(iocb, inode, iter, offset, blkdev_get_block,
NULL, DIO_SKIP_DIO_COUNT);
+
+ if (IS_HIPRI(inode))
+ iocb->ki_flags |= IOCB_HIPRI;
return __blockdev_direct_IO(iocb, inode, I_BDEV(inode), iter, offset,
blkdev_get_block, NULL, NULL,
DIO_SKIP_DIO_COUNT);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 70e61b5..8ae39ea 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1788,6 +1788,7 @@ struct super_operations {
#else
#define S_DAX 0 /* Make all the DAX code disappear */
#endif
+#define S_HIPRI 16384 /* IO for this file has high priority */
/*
* Note that nosuid etc flags are inode-specific: setting some file-system
@@ -1826,6 +1827,7 @@ struct super_operations {
#define IS_AUTOMOUNT(inode) ((inode)->i_flags & S_AUTOMOUNT)
#define IS_NOSEC(inode) ((inode)->i_flags & S_NOSEC)
#define IS_DAX(inode) ((inode)->i_flags & S_DAX)
+#define IS_HIPRI(inode) ((inode)->i_flags & S_HIPRI)
#define IS_WHITEOUT(inode) (S_ISCHR(inode->i_mode) && \
(inode)->i_rdev == WHITEOUT_DEV)
diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h
index a079d50..d6e262c 100644
--- a/include/uapi/linux/fs.h
+++ b/include/uapi/linux/fs.h
@@ -223,6 +223,8 @@ struct fsxattr {
#define BLKROTATIONAL _IO(0x12,126)
#define BLKZEROOUT _IO(0x12,127)
#define BLKDAXGET _IO(0x12,129)
+#define BLKHIPRISET _IOW(0x12,130,int)
+#define BLKHIPRIGET _IO(0x12,131)
#define BMAP_IOCTL 1 /* obsolete - kept for compatibility */
#define FIBMAP _IO(0x00,1) /* bmap access */
--
1.8.3.1
--
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