Re: [PATCH 1/2] btrfs-progs: new "allocation_hint" property.

[Boris Burkov <boris@bur.io>]

On Fri, Dec 17, 2021 at 07:47:04PM +0100, Goffredo Baroncelli wrote:
> From: Goffredo Baroncelli <kreijack@inwind.it>
> 
> Handle the property allocation_hint of a btrfs device. Below
> an example of use:
> 
> $ # set a new value
> $ sudo btrfs property set /dev/vde allocation_hint DATA_ONLY

I applied this patchset to the master branch of
git://github.com/kdave/btrfs-progs.git
and this command failed with something like "not a btrfs object".

However, it worked fine as:
$ sudo btrfs property set -t device /dev/DEV allocation_hint DATA_ONLY

I can't think of a reason I would hit this error and you wouldn't, since
that check is relatively old, but figured I would mention it.

> 
> $ # get the current value
> $ sudo btrfs property get /dev/vde allocation_hint
> devid=4, path=/dev/vde: allocation_hint=DATA_ONLY
> 
> The following values are availables:
> - DATA_ONLY
> - PREFERRED_DATA (default)
> - PREFERRED_METADATA
> - METADATA_ONLY
> 
> Root privileges are required.
> 
> Signed-off-by: Goffredo Baroncelli <kreijack@inwind.it>
> ---
>  cmds/property.c       | 204 ++++++++++++++++++++++++++++++++++++++++++
>  kernel-shared/ctree.h |  13 +++
>  2 files changed, 217 insertions(+)
> 
> diff --git a/cmds/property.c b/cmds/property.c
> index 59ef997c..e6a38ee1 100644
> --- a/cmds/property.c
> +++ b/cmds/property.c
> @@ -22,6 +22,7 @@
>  #include <sys/ioctl.h>
>  #include <sys/stat.h>
>  #include <sys/xattr.h>
> +#include <sys/sysmacros.h>
>  #include <uuid/uuid.h>
>  #include <btrfsutil.h>
>  #include "cmds/commands.h"
> @@ -30,6 +31,7 @@
>  #include "common/open-utils.h"
>  #include "common/utils.h"
>  #include "common/help.h"
> +#include "common/path-utils.h"
>  
>  #define XATTR_BTRFS_PREFIX     "btrfs."
>  #define XATTR_BTRFS_PREFIX_LEN (sizeof(XATTR_BTRFS_PREFIX) - 1)
> @@ -232,6 +234,202 @@ out:
>  	return ret;
>  }
>  
> +static int btrfs_find_devid_and_mnt(const char *devpath, int *devid,
> +				    char *path, int maxpath)
> +{
> +	int ret, i, fd;
> +	DIR *dir;
> +	struct stat stdevpath;
> +	struct btrfs_ioctl_fs_info_args fi_args;
> +	struct btrfs_ioctl_dev_info_args dev_info;
> +
> +	ret = get_btrfs_mount(devpath, path, maxpath);
> +	if (ret)
> +		return ret;
> +
> +	fd = btrfs_open_dir(path, &dir, 1);
> +	if (fd < 0)
> +		return fd;
> +
> +	ret = stat(devpath, &stdevpath);
> +	if (ret) {
> +		error("cannot stat '%s'", devpath);
> +		goto out;
> +	}
> +
> +	ret = ioctl(fd, BTRFS_IOC_FS_INFO, &fi_args);
> +	if (ret < 0) {
> +		if (errno == EPERM)
> +			return -errno;
> +		error("cannot get filesystem info: %m");
> +		ret = -10;
> +		goto out;
> +	}
> +
> +	for (i = 0 ; i <= fi_args.max_id ; i++) {
> +		struct stat st;
> +
> +		memset(&dev_info, 0, sizeof(dev_info));
> +		ret = get_device_info(fd, i, &dev_info);
> +		if (ret == -ENODEV)
> +			continue;
> +		if (ret) {
> +			error("cannot get info about device devid=%d", i);
> +			goto out;
> +		}
> +
> +		if (!dev_info.path)
> +			/* missing devices */
> +			continue;
> +
> +		ret = stat((char *)dev_info.path, &st);
> +		if (ret) {
> +			error("cannot stat '%s'", devpath);
> +			goto out;
> +		}
> +
> +		if (major(st.st_rdev) == major(stdevpath.st_rdev) &&
> +		    minor(st.st_rdev) == minor(stdevpath.st_rdev)) {
> +			*devid = dev_info.devid;
> +			ret = 0;
> +			goto out;
> +		}
> +	}
> +
> +	ret = -12;
> +
> +out:
> +	close_file_or_dir(fd, dir);
> +	return ret;
> +}
> +
> +static struct ull_charp_pair_t {
> +	u64		value;
> +	const char	*descr;
> +} allocation_hint_description[] = {
> +	{BTRFS_DEV_ALLOCATION_HINT_PREFERRED_METADATA, "PREFERRED_METADATA"},
> +	{BTRFS_DEV_ALLOCATION_HINT_METADATA_ONLY, "METADATA_ONLY"},
> +	{BTRFS_DEV_ALLOCATION_HINT_PREFERRED_DATA, "PREFERRED_DATA"},
> +	{BTRFS_DEV_ALLOCATION_HINT_DATA_ONLY, "DATA_ONLY"},
> +	{0, NULL}
> +};
> +
> +static int prop_allocation_hint(enum prop_object_type type,
> +				const char *object,
> +				const char *name,
> +				const char *value,
> +				bool force)
> +{
> +	int ret, devid, fd, fd2;
> +	char path[PATH_MAX];
> +	DIR *dir;
> +	u8 fsid[BTRFS_UUID_SIZE];
> +	char fsid_str[BTRFS_UUID_UNPARSED_SIZE];
> +	char sysfs_file[PATH_MAX];
> +	char filename[PATH_MAX];
> +	int i;
> +	u64 v, devtype;
> +	char buf[1024];
> +
> +	ret = btrfs_find_devid_and_mnt(object, &devid, path, sizeof(path));
> +	if (ret)
> +		return -5;
> +
> +	fd = btrfs_open_dir(path, &dir, 1);
> +	if (fd < 0)
> +		return fd;
> +
> +	ret = get_fsid_fd(fd, fsid);
> +	if (ret < 0)
> +		goto out;
> +
> +	uuid_unparse(fsid, fsid_str);
> +	sprintf(filename, "devinfo/%d/allocation_hint", devid);
> +
> +	/* build /sys/fs/btrfs/<UUID>/devinfo/<DEVID>/type */
> +	ret = path_cat3_out(sysfs_file, "/sys/fs/btrfs", fsid_str, filename);
> +	if (ret < 0)
> +		goto out;
> +
> +	fd2 = open(sysfs_file, O_RDONLY);
> +	if (fd2 < 0) {
> +		error("'allocation_hint' property not available or accessible.");
> +		ret = -errno;
> +		goto out;
> +	}
> +
> +	ret = read(fd2, buf, sizeof(buf) - 1);
> +	close(fd2);
> +	if (ret < 0) {
> +		error("Unable to read the 'allocation_hint' property.");
> +		ret = -errno;
> +		goto out;
> +	}
> +
> +	buf[sizeof(buf) - 1] = 0;
> +	devtype = strtoull(buf, NULL, 0);
> +
> +	if (!value) {
> +		/* READ */
> +		for (i = 0 ; allocation_hint_description[i].descr ; i++)
> +			if (devtype == allocation_hint_description[i].value)
> +				break;
> +		if (allocation_hint_description[i].descr)
> +			printf("devid=%d, path=%s: allocation_hint=%s\n",
> +				devid, object,
> +				allocation_hint_description[i].descr);
> +		else
> +			printf("devid=%d, path=%s: allocation_hint=unknown:%llu\n",
> +				devid, object,
> +				devtype);
> +		ret = 0;
> +	} else {
> +		/* WRITE */
> +		for (i = 0 ; allocation_hint_description[i].descr ; i++)
> +			if (!strcmp(value, allocation_hint_description[i].descr))
> +				break;
> +
> +		if (allocation_hint_description[i].descr) {
> +			v = allocation_hint_description[i].value;
> +		} else if (sscanf(value, "%llu", &v) != 1) {
> +			error("Invalid value '%s'\n", value);
> +			ret = -3;
> +			goto out;
> +		} 
> +		if (v & ~BTRFS_DEV_ALLOCATION_HINT_MASK) {
> +			error("Invalid value '%s'\n", value);
> +			ret = -3;
> +			goto out;
> +		}
> +
> +		devtype &= ~BTRFS_DEV_ALLOCATION_HINT_MASK;
> +		devtype |= (v & BTRFS_DEV_ALLOCATION_HINT_MASK);
> +
> +		fd2 = open(sysfs_file, O_RDWR);
> +		if (fd2 < 0) {
> +			error("'allocation_hint' property not available or accessible for updating.");
> +			ret = -errno;
> +			goto out;
> +		}
> +
> +		sprintf(buf, "%llu", devtype);
> +
> +		ret = write(fd2, buf, strlen(buf));
> +		close(fd2);
> +		if (ret < 0) {
> +			error("Unable to update 'allocation_hint' property.");
> +			ret = -errno;
> +			goto out;
> +		}
> +
> +	}
> +
> +	ret = 0;
> +out:
> +	close_file_or_dir(fd, dir);
> +	return ret;
> +}
> +
>  const struct prop_handler prop_handlers[] = {
>  	{
>  		.name ="ro",
> @@ -254,6 +452,12 @@ const struct prop_handler prop_handlers[] = {
>  		.types = prop_object_inode,
>  		.handler = prop_compression
>  	},
> +	{
> +		.name = "allocation_hint",
> +		.desc = "hint to store the data/metadata chunks",
> +		.types = prop_object_dev,
> +		.handler = prop_allocation_hint
> +	},
>  	{NULL, NULL, 0, 0, NULL}
>  };
>  
> diff --git a/kernel-shared/ctree.h b/kernel-shared/ctree.h
> index 966490d3..adc869fe 100644
> --- a/kernel-shared/ctree.h
> +++ b/kernel-shared/ctree.h
> @@ -213,6 +213,19 @@ struct btrfs_mapping_tree {
>  	struct cache_tree cache_tree;
>  };
>  
> +/* btrfs chunk allocation hints */
> +#define BTRFS_DEV_ALLOCATION_HINT_BIT_COUNT    2
> +#define BTRFS_DEV_ALLOCATION_HINT_MASK ((1ULL << \
> +	       BTRFS_DEV_ALLOCATION_HINT_BIT_COUNT) - 1)
> +/* preferred metadata chunk, but data chunk allowed */
> +#define BTRFS_DEV_ALLOCATION_HINT_PREFERRED_METADATA        (1ULL)
> +/* only metadata chunk are allowed */
> +#define BTRFS_DEV_ALLOCATION_HINT_METADATA_ONLY     (2ULL)
> +/* only data chunk allowed */
> +#define BTRFS_DEV_ALLOCATION_HINT_DATA_ONLY         (3ULL)
> +/* preferred data chunk, but metadata chunk allowed */
> +#define BTRFS_DEV_ALLOCATION_HINT_PREFERRED_DATA    (0ULL)
> +
>  #define BTRFS_UUID_SIZE 16
>  struct btrfs_dev_item {
>  	/* the internal btrfs device id */
> -- 
> 2.34.1
>