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[PATCH, RFC] mkfs.xfs: go into multidisk mode when geometry is on cmdline

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[PATCH, RFC] mkfs.xfs: go into multidisk mode when geometry is on cmdline

Eric Sandeen-3
In the course of some other investigations, I found that
calc_default_ag_geometry() doesn't go into "multidisk" mode
unless stripe geometry is *detected* (i.e. by the blkid routines).

Specifying a geometry on the cmdline is *not* sufficient, because
we test (ft.dsunit | ft.dswidth) which are not set by the cmdline
options.

If we move the AG calculations to after we have set dsunit & dswdith,
then we'll pick up either cmdline-specified or blkid-detected
geometry, and go into "multidisk" mode for AG size/count
calculations in both cases.

So now for a ~5T fs, for example, we'd make several more
AGs:

# truncate --size=5t fsfile
# mkfs.xfs -N -d su=128k,sw=8 fsfile | grep agcount
meta-data=fsfile                 isize=256    agcount=5, agsize=268435424 blks
# mkfs/mkfs.xfs -N -d su=128k,sw=8 fsfile | grep agcount
meta-data=fsfile                 isize=256    agcount=32, agsize=41943008 blks

Signed-off-by: Eric Sandeen <[hidden email]>
---

TBH, though, is there ever any value in treating a very large
fs as "!multidisk?"  When would we ever want to pretend that
a 16T filesystem doesn't have a lot of spindles behind it?

diff --git a/mkfs/xfs_mkfs.c b/mkfs/xfs_mkfs.c
index be931e3..42a7b5b 100644
--- a/mkfs/xfs_mkfs.c
+++ b/mkfs/xfs_mkfs.c
@@ -2090,25 +2091,6 @@ _("size %s specified for log subvolume is too large, maximum is %lld blocks\n"),
  nbmblocks = 0;
  }
 
- if (dasize) { /* User-specified AG size */
- /*
- * Check specified agsize is a multiple of blocksize.
- */
- if (agsize % blocksize) {
- fprintf(stderr,
- _("agsize (%lld) not a multiple of fs blk size (%d)\n"),
- (long long)agsize, blocksize);
- usage();
- }
- agsize /= blocksize;
- agcount = dblocks / agsize + (dblocks % agsize != 0);
-
- } else if (daflag) /* User-specified AG count */
- agsize = dblocks / agcount + (dblocks % agcount != 0);
- else
- calc_default_ag_geometry(blocklog, dblocks,
- ft.dsunit | ft.dswidth, &agsize, &agcount);
-
  if (!nodsflag) {
  if (dsunit) {
  if (ft.dsunit && ft.dsunit != dsunit) {
@@ -2132,6 +2114,25 @@ _("size %s specified for log subvolume is too large, maximum is %lld blocks\n"),
  }
  } /* else dsunit & dswidth can't be set if nodsflag is set */
 
+ if (dasize) { /* User-specified AG size */
+ /*
+ * Check specified agsize is a multiple of blocksize.
+ */
+ if (agsize % blocksize) {
+ fprintf(stderr,
+ _("agsize (%lld) not a multiple of fs blk size (%d)\n"),
+ (long long)agsize, blocksize);
+ usage();
+ }
+ agsize /= blocksize;
+ agcount = dblocks / agsize + (dblocks % agsize != 0);
+
+ } else if (daflag) /* User-specified AG count */
+ agsize = dblocks / agcount + (dblocks % agcount != 0);
+ else
+ calc_default_ag_geometry(blocklog, dblocks,
+ dsunit | dswidth, &agsize, &agcount);
+
  /*
  * If dsunit is a multiple of fs blocksize, then check that is a
  * multiple of the agsize too

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Re: [PATCH, RFC] mkfs.xfs: go into multidisk mode when geometry is on cmdline

Christoph Hellwig
On Tue, Nov 20, 2012 at 10:34:29AM -0600, Eric Sandeen wrote:
> So now for a ~5T fs, for example, we'd make several more
> AGs:
>
> # truncate --size=5t fsfile
> # mkfs.xfs -N -d su=128k,sw=8 fsfile | grep agcount
> meta-data=fsfile                 isize=256    agcount=5, agsize=268435424 blks
> # mkfs/mkfs.xfs -N -d su=128k,sw=8 fsfile | grep agcount
> meta-data=fsfile                 isize=256    agcount=32, agsize=41943008 blks

Can you add this to xfstests, please?

> TBH, though, is there ever any value in treating a very large
> fs as "!multidisk?"  When would we ever want to pretend that
> a 16T filesystem doesn't have a lot of spindles behind it?

Not now, but I'm pretty sure we'll get there not too soon in the
future.

> + } else if (daflag) /* User-specified AG count */
> + agsize = dblocks / agcount + (dblocks % agcount != 0);
> + else
> + calc_default_ag_geometry(blocklog, dblocks,
> + dsunit | dswidth, &agsize, &agcount);
> +

I know the code was just moved, but can you add braces to the else if
constructs so that the whole if else if else has consistent bracing?

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