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Re: [PATCH] mkfs.xfs: always use underlying fs sector size when mkfs'ing

To: Eric Sandeen <sandeen@xxxxxxxxxx>
Subject: Re: [PATCH] mkfs.xfs: always use underlying fs sector size when mkfs'ing a file
From: Jan Tulak <jtulak@xxxxxxxxxx>
Date: Thu, 18 Jun 2015 07:03:39 -0400 (EDT)
Cc: xfs-oss <xfs@xxxxxxxxxxx>
Delivered-to: xfs@xxxxxxxxxxx
In-reply-to: <55820229.1010701@xxxxxxxxxx>
References: <55820229.1010701@xxxxxxxxxx>
Thread-index: wQ4bnSEuHFVeYITTiH9NlcfTuAccGQ==
Thread-topic: mkfs.xfs: always use underlying fs sector size when mkfs'ing a file

----- Original Message -----
> From: "Eric Sandeen" <sandeen@xxxxxxxxxx>
> To: "xfs-oss" <xfs@xxxxxxxxxxx>
> Sent: Thursday, June 18, 2015 1:26:33 AM
> Subject: [PATCH] mkfs.xfs: always use underlying fs sector size when mkfs'ing 
> a file
> 
> If we are mkfs'ing a file, and that file is on a 4k sector filesystem,
> we should make the fs image file with the same sector size, or things
> may fail when they try to do direct IO in 512 byte chunks (depending
> on whether it is a 512e or "hard" 4k device).
> 
> Earlier commits attempted this to some degree:
> 
> 5a7d59 xfsprogs: try to handle mkfs of a file on 4k sector device
> 3800a2 mkfs.xfs: don't call blkid_get_topology on existing regular files
> 
> but inexplicably missed the case where mkfs.xfs with "-d file" was
> specified.
> 
> One more try; in get_topology(), try to get the underlying fs sector
> size in *all* cases where we are mkfs'ing a file, and set the sector size
> accordingly.
> 
> Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
> ---
> 
> (This does it for 512e as well as hard 4k drives, but I think that's
> probably ok?  If not, perhaps we should go further and attempt to
> discern logical and physical sectors for the device under the
> filesystem.  Is it worth it?  Not sure it is.)
> 
> diff --git a/mkfs/xfs_mkfs.c b/mkfs/xfs_mkfs.c
> index e2a052d..e44c390 100644
> --- a/mkfs/xfs_mkfs.c
> +++ b/mkfs/xfs_mkfs.c
> @@ -462,31 +462,34 @@ static void get_topology(
>       struct fs_topology      *ft,
>       int                     force_overwrite)
>  {
> -     if (!xi->disfile) {
> -             char *dfile = xi->volname ? xi->volname : xi->dname;
> -             struct stat statbuf;
> +     struct stat statbuf;
> +     char *dfile = xi->volname ? xi->volname : xi->dname;
>  
> -             /*
> -              * If our target is a regular file, and xi->disfile isn't
> -              * set (i.e. no "-d file" invocation), use platform_findsizes
> -              * to try to obtain the underlying filesystem's requirements
> -              * for direct IO; we'll set our sector size to that if possible.
> -              */
> -             if (!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);
> -                     }
> -             } else {
> -                     blkid_get_topology(dfile, &ft->dsunit, &ft->dswidth,
> -                                        &ft->lsectorsize, &ft->psectorsize,
> -                                        force_overwrite);
> +     /*
> +      * If our target is a regular file, use platform_findsizes
> +      * to try to obtain the underlying filesystem's requirements
> +      * for direct IO; we'll set our sector size to that if possible.
> +      */
> +     if (xi->disfile ||
> +         (!stat(dfile, &statbuf) && S_ISREG(statbuf.st_mode))) {
> +             int fd;
> +             int flags = O_RDONLY;
> +             long long dummy;
> +
> +             /* with xi->disfile we may not have the file yet! */
> +             if (xi->disfile)
> +                     flags |= O_CREAT;
> +
> +             fd = open(dfile, flags, 0666);
> +             if (fd >= 0) {
> +                     platform_findsizes(dfile, fd, &dummy, &ft->lsectorsize);
> +                     close (fd);
>               }
> +
> +     } else {
> +             blkid_get_topology(dfile, &ft->dsunit, &ft->dswidth,
> +                                &ft->lsectorsize, &ft->psectorsize,
> +                                force_overwrite);
>       }
>  
>       if (xi->rtname && !xi->risfile) {
> 

This changes get_topology only for ENABLE_BLKID branch of #ifdef. Is that 
intentional, i.e. we don't expect anyone not using ENABLE_BLKID? Because 
otherwise, if mkfs is compiled without ENABLE_BLKID, then all we get is:

        int bsz = BBSIZE;

        if (!xi->disfile) {
                int fd;
                long long dummy;

                get_subvol_stripe_wrapper(dfile, SVTYPE_DATA,
                                &ft->dsunit, &ft->dswidth, &ft->sectoralign);
                fd = open(dfile, O_RDONLY);
                /* If this fails we just fall back to BBSIZE */
                if (fd >= 0) {
                        platform_findsizes(dfile, fd, &dummy, &bsz);
                        close(fd);
                }
        }

        ft->lsectorsize = bsz;
        ft->psectorsize = bsz;

Two definitions of get_topology looks really unfortunate - this is something I 
have on my radar to change.
-- 
Jan Tulak
jtulak@xxxxxxxxxx

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