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Re: [RFC PATCH 3/4] xfs: add FREE_EOFBLOCKS ioctl

To: Dave Chinner <david@xxxxxxxxxxxxx>
Subject: Re: [RFC PATCH 3/4] xfs: add FREE_EOFBLOCKS ioctl
From: Brian Foster <bfoster@xxxxxxxxxx>
Date: Tue, 04 Sep 2012 10:10:35 -0400
Cc: xfs@xxxxxxxxxxx
In-reply-to: <20120903051742.GS15292@dastard>
References: <1346097111-4476-1-git-send-email-bfoster@xxxxxxxxxx> <1346097111-4476-4-git-send-email-bfoster@xxxxxxxxxx> <20120903051742.GS15292@dastard>
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On 09/03/2012 01:17 AM, Dave Chinner wrote:
> On Mon, Aug 27, 2012 at 03:51:50PM -0400, Brian Foster wrote:
>> The XFS_IOC_FREE_EOFBLOCKS ioctl allows users to invoke an EOFBLOCKS
>> scan. The xfs_eofblocks structure is defined to support the command
>> parameters (quota type/id and minimum file size).
>>
>> Signed-off-by: Brian Foster <bfoster@xxxxxxxxxx>
>> ---
>>  fs/xfs/xfs_fs.h       |   10 ++++++++++
>>  fs/xfs/xfs_ioctl.c    |   25 +++++++++++++++++++++++++
>>  fs/xfs/xfs_quota.h    |    1 +
>>  fs/xfs/xfs_quotaops.c |    2 +-
>>  4 files changed, 37 insertions(+), 1 deletions(-)
>>
>> diff --git a/fs/xfs/xfs_fs.h b/fs/xfs/xfs_fs.h
>> index c13fed8..6f93db9 100644
>> --- a/fs/xfs/xfs_fs.h
>> +++ b/fs/xfs/xfs_fs.h
>> @@ -339,6 +339,15 @@ typedef struct xfs_error_injection {
>>  
>>  
>>  /*
>> + * Speculative preallocation trimming.
>> + */
>> +typedef struct xfs_eofblocks {
>> +    __u32           id;             /* quota id */
>> +    __u32           qtype;          /* quota type */
>> +    __u64           min_file_size;  /* minimum file size */
>> +} xfs_eofblocks_t;
> 
> No typedefs.
> 

This is something I see throughout the code that I haven't quite
followed (i.e., using the _t typedefs vs. not). Is the general consensus
to move away from typedefs when possible?

...
>> +    case XFS_IOC_FREE_EOFBLOCKS: {
>> +            struct xfs_eofblocks eofb;
>> +            int qtype;
>> +
>> +            if (copy_from_user(&eofb, arg, sizeof(eofb)))
>> +                    return -XFS_ERROR(EFAULT);
>> +
>> +            qtype = xfs_quota_type(eofb.qtype);
>> +
>> +            /*
>> +             * TODO: The filtering code currently uses the id in the inode.
>> +             * Therefore, I don't think it really matters whether the
>> +             * particular quota type is enabled (and the dquot is attached).
>> +             *
>> +             * Alternatively, we could filter by dquot type. This would
>> +             * mean we might have to make sure dquot's are attached during
>> +             * the scan and that the particular quota type is enabled. I'm
>> +             * not sure that this buys us anything.
>> +             */
> 
> If quota is not enabled, then a request to free blocks determined by
> a quota ID is invalid and should be rejected. It's a user API - what
> is and isn't supported needs to be written down in black and white
> (i.e. in the xfsctl man page).
> 

Ok. I was thinking that we could support the ability to scan by uid/gid
regardless of whether quota is enabled, but perhaps there's no purpose
to that if a quota isn't enabled.

Brian

>> +            /* TODO: might want to just use the eofb structure here */
>> +            error = xfs_inodes_free_eofblocks(mp, qtype, eofb.id, 
>> eofb.min_file_size, EOFBLOCKS_WAIT);
> 
> Yes, just pass the structure - it means it can be passed all the way
> down to the execute function, and only that code needs to handle
> different versions of the structure.
> 
> Cheers,
> 
> Dave.
> 

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