[PATCH] btrfs-progs: create helper function to use lblkid to scan for btrfs disks

[PATCH] btrfs-progs: create helper function to use lblkid to scan for btrfs disks

[Anand Jain]

Signed-off-by: Anand Jain <anand.jain@oracle.com>
---
 utils.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 utils.h |  2 ++
 2 files changed, 56 insertions(+)

diff --git a/utils.c b/utils.c
index c6022fc..ccb5199 100644
--- a/utils.c
+++ b/utils.c
@@ -1914,6 +1914,57 @@ int test_dev_for_mkfs(char *file, int force_overwrite, char *estr)
 	return 0;
 }
 
+int test_skip_this_disk(char *path)
+{
+	int fd;
+	/* this will eliminate disks which are mounted (btrfs)
+	 * and non-dm disk path when dm is enabled
+	 */
+	fd = open(path, O_RDWR|O_EXCL);
+	if (fd < 0)
+		return 1;
+	close(fd);
+	return 0;
+}
+
+int btrfs_scan_lblkid(int update_kernel)
+{
+	int fd = -1;
+	u64 num_devices;
+	struct btrfs_fs_devices *tmp_devices;
+	blkid_dev_iterate iter = NULL;
+	blkid_dev dev = NULL;
+	blkid_cache cache = NULL;
+	char path[PATH_MAX];
+
+	if (blkid_get_cache(&cache, 0) < 0) {
+		printf("ERROR: lblkid cache get failed\n");
+		return 1;
+	}
+	blkid_probe_all(cache);
+	iter = blkid_dev_iterate_begin(cache);
+	blkid_dev_set_search(iter, "TYPE", "btrfs");
+	while (blkid_dev_next(iter, &dev) == 0) {
+		dev = blkid_verify(cache, dev);
+		if (!dev)
+			continue;
+		/* if we are here its definitly a btrfs disk*/
+		strcpy(path, blkid_dev_devname(dev));
+		if (test_skip_this_disk(path))
+			continue;
+
+		fd = open(path, O_RDONLY);
+		btrfs_scan_one_device(fd, path, &tmp_devices,
+				&num_devices, BTRFS_SUPER_INFO_OFFSET);
+		close(fd);
+		fd = -1;
+		if (update_kernel)
+			btrfs_register_one_device(path);
+	}
+	blkid_dev_iterate_end(iter);
+	return 0;
+}
+
 /*
  * scans devs for the btrfs
 */
@@ -1928,6 +1979,9 @@ int scan_for_btrfs(int where, int update_kernel)
 	case BTRFS_SCAN_DEV:
 		ret = btrfs_scan_one_dir("/dev", update_kernel);
 		break;
+	case BTRFS_SCAN_LBLKID:
+		ret = btrfs_scan_lblkid(update_kernel);
+		break;
 	}
 	return ret;
 }
diff --git a/utils.h b/utils.h
index e944685..0f31db7 100644
--- a/utils.h
+++ b/utils.h
@@ -28,6 +28,7 @@
 #define BTRFS_SCAN_PROC		(1ULL << 0)
 #define BTRFS_SCAN_DEV		(1ULL << 1)
 #define BTRFS_SCAN_MOUNTED	(1ULL << 2)
+#define BTRFS_SCAN_LBLKID	(1ULL << 3)
 
 #define BTRFS_UPDATE_KERNEL	1
 
@@ -89,5 +90,6 @@ int csum_tree_block(struct btrfs_root *root, struct extent_buffer *buf,
 			   int verify);
 int ask_user(char *question);
 int lookup_ino_rootid(int fd, u64 *rootid);
+int btrfs_scan_lblkid(int update_kernel);
 
 #endif
-- 
1.8.4.rc4.1.g0d8beaa

Re: [PATCH] btrfs-progs: create helper function to use lblkid to scan for btrfs disks

[Anand Jain]

  Following this patch the idea is to use lblkid to scan
  for the btrfs disks by default which means we don't
  use BTRFS_SCAN_PROC any more.
  which implies commands btrfs filesystem show and btrfs device scan will
  use lblkid to scan disks instead of current /proc/partitions
  by default.

  So now the question is, if there is any need to have option to scan
  using /proc/partitions ? and instead of removing it completely
  would we need it under a new option '-p' (in filesystem show and
  device  scan) so that user can use /proc/partitions when needed,
  I really don't know what would be that circumstance though,

  Any thoughts?

Thanks Anand



On 09/27/2013 11:45 PM, Anand Jain wrote:
> Signed-off-by: Anand Jain <anand.jain@oracle.com>
> ---
>   utils.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>   utils.h |  2 ++
>   2 files changed, 56 insertions(+)
>
> diff --git a/utils.c b/utils.c
> index c6022fc..ccb5199 100644
> --- a/utils.c
> +++ b/utils.c
> @@ -1914,6 +1914,57 @@ int test_dev_for_mkfs(char *file, int force_overwrite, char *estr)
>   	return 0;
>   }
>
> +int test_skip_this_disk(char *path)
> +{
> +	int fd;
> +	/* this will eliminate disks which are mounted (btrfs)
> +	 * and non-dm disk path when dm is enabled
> +	 */
> +	fd = open(path, O_RDWR|O_EXCL);
> +	if (fd < 0)
> +		return 1;
> +	close(fd);
> +	return 0;
> +}
> +
> +int btrfs_scan_lblkid(int update_kernel)
> +{
> +	int fd = -1;
> +	u64 num_devices;
> +	struct btrfs_fs_devices *tmp_devices;
> +	blkid_dev_iterate iter = NULL;
> +	blkid_dev dev = NULL;
> +	blkid_cache cache = NULL;
> +	char path[PATH_MAX];
> +
> +	if (blkid_get_cache(&cache, 0) < 0) {
> +		printf("ERROR: lblkid cache get failed\n");
> +		return 1;
> +	}
> +	blkid_probe_all(cache);
> +	iter = blkid_dev_iterate_begin(cache);
> +	blkid_dev_set_search(iter, "TYPE", "btrfs");
> +	while (blkid_dev_next(iter, &dev) == 0) {
> +		dev = blkid_verify(cache, dev);
> +		if (!dev)
> +			continue;
> +		/* if we are here its definitly a btrfs disk*/
> +		strcpy(path, blkid_dev_devname(dev));
> +		if (test_skip_this_disk(path))
> +			continue;
> +
> +		fd = open(path, O_RDONLY);
> +		btrfs_scan_one_device(fd, path, &tmp_devices,
> +				&num_devices, BTRFS_SUPER_INFO_OFFSET);
> +		close(fd);
> +		fd = -1;
> +		if (update_kernel)
> +			btrfs_register_one_device(path);
> +	}
> +	blkid_dev_iterate_end(iter);
> +	return 0;
> +}
> +
>   /*
>    * scans devs for the btrfs
>   */
> @@ -1928,6 +1979,9 @@ int scan_for_btrfs(int where, int update_kernel)
>   	case BTRFS_SCAN_DEV:
>   		ret = btrfs_scan_one_dir("/dev", update_kernel);
>   		break;
> +	case BTRFS_SCAN_LBLKID:
> +		ret = btrfs_scan_lblkid(update_kernel);
> +		break;
>   	}
>   	return ret;
>   }
> diff --git a/utils.h b/utils.h
> index e944685..0f31db7 100644
> --- a/utils.h
> +++ b/utils.h
> @@ -28,6 +28,7 @@
>   #define BTRFS_SCAN_PROC		(1ULL << 0)
>   #define BTRFS_SCAN_DEV		(1ULL << 1)
>   #define BTRFS_SCAN_MOUNTED	(1ULL << 2)
> +#define BTRFS_SCAN_LBLKID	(1ULL << 3)
>
>   #define BTRFS_UPDATE_KERNEL	1
>
> @@ -89,5 +90,6 @@ int csum_tree_block(struct btrfs_root *root, struct extent_buffer *buf,
>   			   int verify);
>   int ask_user(char *question);
>   int lookup_ino_rootid(int fd, u64 *rootid);
> +int btrfs_scan_lblkid(int update_kernel);
>
>   #endif
>

Re: [PATCH] btrfs-progs: create helper function to use lblkid to scan for btrfs disks

[Wang Shilong]

Helo Anand,
> 
> 
> Following this patch the idea is to use lblkid to scan
> for the btrfs disks by default which means we don't
> use BTRFS_SCAN_PROC any more.


Firstly, i would like to know if we will get any different results between scanning
/proc/partions and using lbkid.

If not, why we can use liblkid totally,since this is more simple.

Thanks,
Wang
> which implies commands btrfs filesystem show and btrfs device scan will
> use lblkid to scan disks instead of current /proc/partitions
> by default.
> 
> So now the question is, if there is any need to have option to scan
> using /proc/partitions ? and instead of removing it completely
> would we need it under a new option '-p' (in filesystem show and
> device  scan) so that user can use /proc/partitions when needed,
> I really don't know what would be that circumstance though,
> 
> Any thoughts?
> 
> Thanks Anand
> 
> 
> 
> On 09/27/2013 11:45 PM, Anand Jain wrote:
>> Signed-off-by: Anand Jain <anand.jain@oracle.com>
>> ---
>>  utils.c | 54 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
>>  utils.h |  2 ++
>>  2 files changed, 56 insertions(+)
>> 
>> diff --git a/utils.c b/utils.c
>> index c6022fc..ccb5199 100644
>> --- a/utils.c
>> +++ b/utils.c
>> @@ -1914,6 +1914,57 @@ int test_dev_for_mkfs(char *file, int force_overwrite, char *estr)
>>  	return 0;
>>  }
>> 
>> +int test_skip_this_disk(char *path)
>> +{
>> +	int fd;
>> +	/* this will eliminate disks which are mounted (btrfs)
>> +	 * and non-dm disk path when dm is enabled
>> +	 */
>> +	fd = open(path, O_RDWR|O_EXCL);
>> +	if (fd < 0)
>> +		return 1;
>> +	close(fd);
>> +	return 0;
>> +}
>> +
>> +int btrfs_scan_lblkid(int update_kernel)
>> +{
>> +	int fd = -1;
>> +	u64 num_devices;
>> +	struct btrfs_fs_devices *tmp_devices;
>> +	blkid_dev_iterate iter = NULL;
>> +	blkid_dev dev = NULL;
>> +	blkid_cache cache = NULL;
>> +	char path[PATH_MAX];
>> +
>> +	if (blkid_get_cache(&cache, 0) < 0) {
>> +		printf("ERROR: lblkid cache get failed\n");
>> +		return 1;
>> +	}
>> +	blkid_probe_all(cache);
>> +	iter = blkid_dev_iterate_begin(cache);
>> +	blkid_dev_set_search(iter, "TYPE", "btrfs");
>> +	while (blkid_dev_next(iter, &dev) == 0) {
>> +		dev = blkid_verify(cache, dev);
>> +		if (!dev)
>> +			continue;
>> +		/* if we are here its definitly a btrfs disk*/
>> +		strcpy(path, blkid_dev_devname(dev));
>> +		if (test_skip_this_disk(path))
>> +			continue;
>> +
>> +		fd = open(path, O_RDONLY);
>> +		btrfs_scan_one_device(fd, path, &tmp_devices,
>> +				&num_devices, BTRFS_SUPER_INFO_OFFSET);
>> +		close(fd);
>> +		fd = -1;
>> +		if (update_kernel)
>> +			btrfs_register_one_device(path);
>> +	}
>> +	blkid_dev_iterate_end(iter);
>> +	return 0;
>> +}
>> +
>>  /*
>>   * scans devs for the btrfs
>>  */
>> @@ -1928,6 +1979,9 @@ int scan_for_btrfs(int where, int update_kernel)
>>  	case BTRFS_SCAN_DEV:
>>  		ret = btrfs_scan_one_dir("/dev", update_kernel);
>>  		break;
>> +	case BTRFS_SCAN_LBLKID:
>> +		ret = btrfs_scan_lblkid(update_kernel);
>> +		break;
>>  	}
>>  	return ret;
>>  }
>> diff --git a/utils.h b/utils.h
>> index e944685..0f31db7 100644
>> --- a/utils.h
>> +++ b/utils.h
>> @@ -28,6 +28,7 @@
>>  #define BTRFS_SCAN_PROC		(1ULL << 0)
>>  #define BTRFS_SCAN_DEV		(1ULL << 1)
>>  #define BTRFS_SCAN_MOUNTED	(1ULL << 2)
>> +#define BTRFS_SCAN_LBLKID	(1ULL << 3)
>> 
>>  #define BTRFS_UPDATE_KERNEL	1
>> 
>> @@ -89,5 +90,6 @@ int csum_tree_block(struct btrfs_root *root, struct extent_buffer *buf,
>>  			   int verify);
>>  int ask_user(char *question);
>>  int lookup_ino_rootid(int fd, u64 *rootid);
>> +int btrfs_scan_lblkid(int update_kernel);
>> 
>>  #endif
>> 
> 
> --
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Re: [PATCH] btrfs-progs: create helper function to use lblkid to scan for btrfs disks

[David Sterba]

On Sat, Sep 28, 2013 at 12:21:51AM +0800, Wang Shilong wrote:
> > Following this patch the idea is to use lblkid to scan
> > for the btrfs disks by default which means we don't
> > use BTRFS_SCAN_PROC any more.
> 
> Firstly, i would like to know if we will get any different results between scanning
> /proc/partions and using lbkid.

I take blkid as a more authoritative source, /proc/partitions was a
workaround to avoid scanning the whole /dev directory.

> If not, why we can use liblkid totally,since this is more simple.

Agreed, blkid by default and --all-devices as a last resort fallback.
The proc workaround can go away.

david

Re: [PATCH] btrfs-progs: create helper function to use lblkid to scan for btrfs disks

[Anand Jain]

>>> Following this patch the idea is to use lblkid to scan
>>> for the btrfs disks by default which means we don't
>>> use BTRFS_SCAN_PROC any more.
>>
>> Firstly, i would like to know if we will get any different results between scanning
>> /proc/partions and using lbkid.
>
> I take blkid as a more authoritative source, /proc/partitions was a
> workaround to avoid scanning the whole /dev directory.
>
>> If not, why we can use liblkid totally,since this is more simple.
>
> Agreed, blkid by default and --all-devices as a last resort fallback.


compiled using BTRFS_SCAN_LBLKID as default.
---
--- a/cmds-filesystem.c
+++ b/cmds-filesystem.c
@@ -402,7 +402,8 @@ static int cmd_show(int argc, char **argv)
         struct list_head *cur_uuid;
         char *search = NULL;
         int ret;
-       int where = BTRFS_SCAN_PROC;
+       int where = BTRFS_SCAN_LBLKID;
         int type = 0;

         while (1) {
------

# btrfs fi show
Label: none  uuid: c114c6ce-58a1-4e2c-839e-b53c5ba5ba75
	Total devices 1 FS bytes used 756.00KiB
	devid    1 size 1.10GiB used 324.00MiB path /dev/mapper/mpathg
---

recompiled to use BTRFS_SCAN_PROC as in original.
---
# btrfs fi show
Label: none  uuid: c114c6ce-58a1-4e2c-839e-b53c5ba5ba75
	Total devices 1 FS bytes used 36.00KiB
	devid    1 size 1.10GiB used 148.62MiB path /dev/dm-2
---


 > The proc workaround can go away.

  The other choice is to use both, 'BTRFS_SCAN_PROC | BTRFS_SCAN_DEV'
  for --all-devices option. in that way proc-way will still be in there.

Thanks, Anand