Re: [PATCH] Fixed getdevinfo() and dlm_ino_hash() to search for the correct disk name.

[Benny Halevy <bhalevy@panasas.com>]

On Jun. 10, 2010, 16:35 +0300, "J. Bruce Fields" <bfields@fieldses.org> wrote:
> On Thu, Jun 10, 2010 at 09:33:37AM -0400, bfields wrote:
>> The patch "pnfsd: fix test in nfsd4_find_pnfs_dlm_device" was obviously
>> correct; before that patch, nfsd4_find_pnfs_dlm_device() returned the
>> first device which did *not* match, instead of the first device which
>> did.
>>
>> Other callers previous worked because they passed int the incorrect
>> name, and because we never had more than one element in the list, so
>> returning the first non-match would return the right thing.
> 
> But then I don't know what point the "/dev/" is serving here.  May as
> well just change the interface so that what's passed in is just the name
> ("sdc2" or whatever)--no use pretending this is some kind of path name
> if it's not really.
> 
> However, I don't know whether passing in the disk name is really a
> sensible way to refer to a filesystem in a user<->kernel api.
> 

up to you...  I think the whole scheme is currently GFS2 specific
and it assumes the device exists symmetrically on /dev/... on all
DSs.  The /dev prefix seems to be completely redundant.
It makes more sense to get rid of it in the user->kernel
API as passed down to nfsd4_set_pnfs_dlm_device() rather than
adding it here.

Benny

> --b.
> 
>>
>> But now we need to fix those callers.
>>
>> From: Eric Anderle <eanderle@umich.edu>
>>
>> ---
>>  fs/nfsd/nfs4pnfsdlm.c |   12 +++++++++---
>>  1 files changed, 9 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/nfsd/nfs4pnfsdlm.c b/fs/nfsd/nfs4pnfsdlm.c
>> index 84caa6e..5a66a71 100644
>> --- a/fs/nfsd/nfs4pnfsdlm.c
>> +++ b/fs/nfsd/nfs4pnfsdlm.c
>> @@ -268,10 +268,13 @@ static int nfsd4_pnfs_dlm_getdevinfo(struct super_block *sb,
>>  	/*
>>  	 * If the DS list has not been established, return -EINVAL
>>  	 */
>> -	dlm_pdev = nfsd4_find_pnfs_dlm_device(sb->s_bdev->bd_disk->disk_name);
>> +	/* Long enough to hold "/dev/" + disk name */
>> +	char full_disk_name[6 + strlen(sb->s_bdev->bd_disk->disk_name)];
>> +	sprintf(full_disk_name, "/dev/%s", sb->s_bdev->bd_disk->disk_name);
>> +	dlm_pdev = nfsd4_find_pnfs_dlm_device(full_disk_name);
>>  	if (!dlm_pdev) {
>>  		dprintk("%s: DEBUG: disk %s Not Found\n", __func__,
>> -			sb->s_bdev->bd_disk->disk_name);
>> +			full_disk_name);
>>  		return err;
>>  	}
>>  
>> @@ -364,7 +367,10 @@ static int dlm_ino_hash(struct inode *ino)
>>  	/* If can't find the inode block device in the pnfs_dlm_deivce list
>>  	 * then don't hand out a layout
>>  	 */
>> -	de = nfsd4_find_pnfs_dlm_device(ino->i_sb->s_bdev->bd_disk->disk_name);
>> +	/* Long enough to hold "/dev/" + disk name */
>> +	char full_disk_name[6 + strlen(ino->i_sb->s_bdev->bd_disk->disk_name)];
>> +	sprintf(full_disk_name, "/dev/%s", ino->i_sb->s_bdev->bd_disk->disk_name);
>> +	de = nfsd4_find_pnfs_dlm_device(full_disk_name);
>>  	if (!de)
>>  		return -1;
>>  	hash_mask = de->num_ds - 1;
>> -- 
>> 1.7.0.4
>>