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Re: [PATCH 2/2 V2] mkfs.xfs: don't call blkid_get_topology on regular fi

To: Brian Foster <bfoster@xxxxxxxxxx>
Subject: Re: [PATCH 2/2 V2] mkfs.xfs: don't call blkid_get_topology on regular files
From: Eric Sandeen <sandeen@xxxxxxxxxxx>
Date: Fri, 06 Jun 2014 10:27:32 -0500
Cc: Eric Sandeen <sandeen@xxxxxxxxxx>, xfs-oss <xfs@xxxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <20140606152059.GB3048@xxxxxxxxxxxxxx>
References: <53852A05.5040006@xxxxxxxxxx> <5390C1B7.7050106@xxxxxxxxxxx> <20140606152059.GB3048@xxxxxxxxxxxxxx>
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.9; rv:24.0) Gecko/20100101 Thunderbird/24.5.0
On 6/6/14, 10:21 AM, Brian Foster wrote:
> On Thu, Jun 05, 2014 at 02:15:03PM -0500, Eric Sandeen wrote:
>> If we encounter a target that's really a regular file,
>> even without "-d file..." on the cmdline, call
>> platform_findsizes() instead of blkid_get_topology to
>> try to discover the "sector size" via the fsgeom() call.
>>
>> Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
>> ---
>>
>> V2: Lose local "isa_file" flag, just switch based on 
>> (xi->disfile) or (stat works & S_ISREG)
>>
>> diff --git a/mkfs/xfs_mkfs.c b/mkfs/xfs_mkfs.c
>> index 188b6b3..3b8bf67 100644
>> --- a/mkfs/xfs_mkfs.c
>> +++ b/mkfs/xfs_mkfs.c
>> @@ -456,9 +456,25 @@ static void get_topology(
>>      struct fs_topology      *ft,
>>      int                     force_overwrite)
>>  {
>> -    if (!xi->disfile) {
>> -            const char *dfile = xi->volname ? xi->volname : xi->dname;
>> +    struct stat statbuf;
>> +    char *dfile = xi->volname ? xi->volname : xi->dname;
>>  
>> +    /*
>> +     * Don't call blkid for topology if this is a "-d file" target, or
>> +     * if we've simply been pointed at a regular file.  platform_findsizes
>> +     * will attempt to find the underlying sector size of the host fs.
>> +     */
>> +    if (xi->disfile ||
>> +        (!stat(dfile, &statbuf) && S_ISREG(statbuf.st_mode))) {
>> +            int fd;
>> +            long long dummy;
>> +
>> +            fd = open(dfile, O_RDONLY);
>> +            if (fd >= 0) {
>> +                    platform_findsizes(dfile, fd, &dummy, &ft->lsectorsize);
>> +                    close(fd);
>> +            }
> 
> The patch looks fine:
> 
> Reviewed-by: Brian Foster <bfoster@xxxxxxxxxx>
> 
> It does look like we'd still be susceptible to error in a situation
> where the file hasn't been created yet (which would occur in
> libxfs_init()).

Hm, let's see - the only way to have mkfs create the file is with the
-d file,name=foo,size=bar invocation.

Sprinkling some printf's into the if/else above, I see:

# rm -f testfile
# mkfs/mkfs.xfs -dfile,name=testfile,size=1g
** doing platform_findsizes **
meta-data=testfile               isize=256    agcount=4, agsize=65536 blks
...

so it looks like the file does get created before we get here.

-Eric

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