Re: [PATCH v4 2/3] btrfs: introduce new device-state read_preferred

From: Anand Jain <anand.jain@oracle.com>
To: linux-btrfs@vger.kernel.org
Cc: dsterba@suse.com, josef@toxicpanda.com
Subject: Re: [PATCH v4 2/3] btrfs: introduce new device-state read_preferred
Date: Thu, 21 Jan 2021 18:19:00 +0800	[thread overview]
Message-ID: <68f27cf6-1c6c-2e93-7078-dfdc569dc4fa@oracle.com> (raw)
In-Reply-To: <151811057c559d9212c7fc55e9c9cbbad1f62f05.1611114341.git.anand.jain@oracle.com>

On 20/1/21 3:52 pm, Anand Jain wrote:
> This is a preparatory patch and introduces a new device flag
> 'read_preferred', RW-able using sysfs interface.
> 
> Signed-off-by: Anand Jain <anand.jain@oracle.com> > ---
> v4: -

There is rb from Josef for this patch in v3.
Could you please add it?

Thanks, Anand

> v2: C style fixes. Drop space in between '! test_bit' and extra lines
>      after it.
> 
>   fs/btrfs/sysfs.c   | 53 ++++++++++++++++++++++++++++++++++++++++++++++
>   fs/btrfs/volumes.h |  1 +
>   2 files changed, 54 insertions(+)
> 
> diff --git a/fs/btrfs/sysfs.c b/fs/btrfs/sysfs.c
> index 7c0324fe97b2..5888e15e3d14 100644
> --- a/fs/btrfs/sysfs.c
> +++ b/fs/btrfs/sysfs.c
> @@ -1422,11 +1422,64 @@ static ssize_t btrfs_devinfo_writeable_show(struct kobject *kobj,
>   }
>   BTRFS_ATTR(devid, writeable, btrfs_devinfo_writeable_show);
>   
> +static ssize_t btrfs_devinfo_read_pref_show(struct kobject *kobj,
> +					    struct kobj_attribute *a, char *buf)
> +{
> +	int val;
> +	struct btrfs_device *device = container_of(kobj, struct btrfs_device,
> +						   devid_kobj);
> +
> +	val = !!test_bit(BTRFS_DEV_STATE_READ_PREFERRED, &device->dev_state);
> +
> +	return snprintf(buf, PAGE_SIZE, "%d\n", val);
> +}
> +
> +static ssize_t btrfs_devinfo_read_pref_store(struct kobject *kobj,
> +					     struct kobj_attribute *a,
> +					     const char *buf, size_t len)
> +{
> +	int ret;
> +	unsigned long val;
> +	struct btrfs_device *device;
> +
> +	ret = kstrtoul(skip_spaces(buf), 0, &val);
> +	if (ret)
> +		return ret;
> +
> +	if (val != 0 && val != 1)
> +		return -EINVAL;
> +
> +	/*
> +	 * lock is not required, the btrfs_device struct can't be freed while
> +	 * its kobject btrfs_device::devid_kobj is still open.
> +	 */
> +	device = container_of(kobj, struct btrfs_device, devid_kobj);
> +
> +	if (val &&
> +	    !test_bit(BTRFS_DEV_STATE_READ_PREFERRED, &device->dev_state)) {
> +		set_bit(BTRFS_DEV_STATE_READ_PREFERRED, &device->dev_state);
> +		btrfs_info(device->fs_devices->fs_info,
> +			   "set read preferred on devid %llu (%d)",
> +			   device->devid, task_pid_nr(current));
> +	} else if (!val &&
> +		   test_bit(BTRFS_DEV_STATE_READ_PREFERRED, &device->dev_state)) {
> +		clear_bit(BTRFS_DEV_STATE_READ_PREFERRED, &device->dev_state);
> +		btrfs_info(device->fs_devices->fs_info,
> +			   "reset read preferred on devid %llu (%d)",
> +			   device->devid, task_pid_nr(current));
> +	}
> +
> +	return len;
> +}
> +BTRFS_ATTR_RW(devid, read_preferred, btrfs_devinfo_read_pref_show,
> +	      btrfs_devinfo_read_pref_store);
> +
>   static struct attribute *devid_attrs[] = {
>   	BTRFS_ATTR_PTR(devid, in_fs_metadata),
>   	BTRFS_ATTR_PTR(devid, missing),
>   	BTRFS_ATTR_PTR(devid, replace_target),
>   	BTRFS_ATTR_PTR(devid, writeable),
> +	BTRFS_ATTR_PTR(devid, read_preferred),
>   	NULL
>   };
>   ATTRIBUTE_GROUPS(devid);
> diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h
> index 71ba1f0e93f4..ea786864b903 100644
> --- a/fs/btrfs/volumes.h
> +++ b/fs/btrfs/volumes.h
> @@ -51,6 +51,7 @@ struct btrfs_io_geometry {
>   #define BTRFS_DEV_STATE_REPLACE_TGT	(3)
>   #define BTRFS_DEV_STATE_FLUSH_SENT	(4)
>   #define BTRFS_DEV_STATE_NO_READA	(5)
> +#define BTRFS_DEV_STATE_READ_PREFERRED	(6)
>   
>   struct btrfs_zoned_device_info;
>   
> 