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Re: [Libguestfs] [PATCH 1/2] New API: vfs_min_size



On Monday 19 October 2015 17:05:02 Maxim Perevedentsev wrote:
> This call provides the way to get minimum size of filesystem.
> This is needed for shrinking. The return units are bytes.
> 
> ---
>  daemon/Makefile.am   |  1 +
>  daemon/daemon.h      |  1 +
>  daemon/fs-min-size.c | 46 ++++++++++++++++++++++++++++++++
>  daemon/ntfs.c        | 75 ++++++++++++++++++++++++++++++++++++++++++++++++++++
>  generator/actions.ml | 16 +++++++++++
>  po/POTFILES          |  1 +
>  src/MAX_PROC_NR      |  2 +-
>  7 files changed, 141 insertions(+), 1 deletion(-)
>  create mode 100644 daemon/fs-min-size.c
> 
> diff --git a/daemon/Makefile.am b/daemon/Makefile.am
> index 4ea3c88..0a01a24 100644
> --- a/daemon/Makefile.am
> +++ b/daemon/Makefile.am
> @@ -116,6 +116,7 @@ guestfsd_SOURCES = \
>  	findfs.c \
>  	fill.c \
>  	find.c \
> +	fs-min-size.c \

Hm not really convinced by the file name chosen, but I cannot find
better options. "size.c"? "fs-size.c"?

>  	fsck.c \
>  	fstrim.c \
>  	glob.c \
> diff --git a/daemon/daemon.h b/daemon/daemon.h
> index 508691a..a690152 100644
> --- a/daemon/daemon.h
> +++ b/daemon/daemon.h
> @@ -283,6 +283,7 @@ extern int btrfs_set_uuid_random (const char *device);
>  /*-- in ntfs.c --*/
>  extern char *ntfs_get_label (const char *device);
>  extern int ntfs_set_label (const char *device, const char *label);
> +extern int64_t ntfs_min_size (const char *device);
> 
>  /*-- in swap.c --*/
>  extern int swap_set_uuid (const char *device, const char *uuid);
> diff --git a/daemon/fs-min-size.c b/daemon/fs-min-size.c
> new file mode 100644
> index 0000000..9c107d1
> --- /dev/null
> +++ b/daemon/fs-min-size.c
> @@ -0,0 +1,46 @@
> +/* libguestfs - the guestfsd daemon
> + * Copyright (C) 2015 Maxim Perevedentsev mperevedentsev virtuozzo com
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License as published by
> + * the Free Software Foundation; either version 2 of the License, or
> + * (at your option) any later version.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program; if not, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
> + */
> +
> +#include <config.h>
> +
> +#include <stdio.h>
> +#include <stdlib.h>
> +#include <unistd.h>
> +
> +#include "daemon.h"
> +#include "actions.h"
> +
> +int64_t
> +do_vfs_min_size(const mountable_t *mountable)

I'd be slightly more verbose here, and call the action like
"vfs_minimum_size".

(also a minor style nitpick: missing space between function name and
the bracket, and in other few places in this patch)

> +{
> +  int64_t r;
> +
> +  /* How we set the label depends on the filesystem type. */
> +  CLEANUP_FREE char *vfs_type = do_vfs_type (mountable);
> +  if (vfs_type == NULL)
> +    return -1;
> +
> +  else if (STREQ (vfs_type, "ntfs"))
> +    r = ntfs_min_size (mountable->device);
> +
> +  else
> +    NOT_SUPPORTED (-1, "don't know how to get minimum size of '%s' filesystems",
> +                   vfs_type);

The documentation might better explicitly mention that unsupported
filesystems will give ENOTSUP as errno on failure.

> +
> +  return r;
> +}
> diff --git a/daemon/ntfs.c b/daemon/ntfs.c
> index 1ead159..b9a645a 100644
> --- a/daemon/ntfs.c
> +++ b/daemon/ntfs.c
> @@ -153,6 +153,81 @@ do_ntfsresize_size (const char *device, int64_t size)
>    return do_ntfsresize (device, size, 0);
>  }
> 
> +int64_t
> +ntfs_min_size (const char *device)
> +{
> +  CLEANUP_FREE char *err = NULL, *out = NULL;
> +  CLEANUP_FREE_STRING_LIST char **lines = NULL;
> +  int r;
> +  size_t i;
> +  char *p;
> +  int64_t ret, volume_size = 0;

The scope of "ret" could be reduced to only the if below where it is
used.

> +  const char *size_pattern = "You might resize at ",
> +             *full_pattern = "Volume is full",
> +             *cluster_size_pattern = "Cluster size",
> +             *volume_size_pattern = "Current volume size:";
> +  int is_full = 0;
> +  int32_t cluster_size = 0;
> +
> +  /* FS may be marked for check, so force ntfsresize */
> +  r = command (&out, &err, str_ntfsresize, "--info", "-ff", device, NULL);
> +
> +  lines = split_lines (out);
> +  if (lines == NULL)
> +    return -1;
> +
> +  if (verbose) {
> +    for (i = 0; lines[i] != NULL; ++i)
> +      fprintf (stderr, "ntfs_min_size: lines[%zu] = \"%s\"\n", i, lines[i]);
> +  }
> +
> +  if (r == -1) {
> +    /* If volume is full, ntfsresize returns error. */
> +    for (i = 0; lines[i] != NULL; ++i) {
> +      if (strstr (lines[i], full_pattern))

Better use STRPREFIX here, which is what we use all around libguestfs.

> +        is_full = 1;
> +      else if ((p = strstr (lines[i], cluster_size_pattern))) {
> +        if (sscanf (p + strlen(cluster_size_pattern),
> +                    "%*[ ]:%" SCNd32, &cluster_size) != 1) {
> +          reply_with_error("Cannot parse cluster size");
> +          return -1;
> +        }
> +      }
> +      else if ((p = strstr (lines[i], volume_size_pattern))) {
> +        if (sscanf (p + strlen(volume_size_pattern),
> +                    "%" SCNd64, &volume_size) != 1) {
> +          reply_with_error("Cannot parse volume size");
> +          return -1;
> +        }

It sounds like these scans of the lines could be done using the
analyze_line helper in btrfs.c (which would need to be moved as common
code in guestfd.c). This way, the parsing of numbers could use
xstrtoul/xstrtoull (see btrfs.c:do_btrfs_subvolume_list) instead of
sscanf.

> +      }
> +    }
> +    if (is_full) {
> +      /* Ceil to cluster size */
> +      if (cluster_size == 0) {
> +        reply_with_error("Bad cluster size");
> +        return -1;
> +      }
> +      return (volume_size + cluster_size - 1) / cluster_size * cluster_size;

Can you please explain (e.g. in a comment) what is this calculation for?

> +    }
> +
> +    reply_with_error ("%s", err);
> +    return -1;
> +  }
> +
> +  for (i = 0; lines[i] != NULL; ++i) {
> +    if ((p = strstr (lines[i], size_pattern))) {
> +      if (sscanf (p + strlen(size_pattern), "%" SCNd64, &ret) != 1) {
> +        reply_with_error("Cannot parse minimum size");
> +        return -1;

Same notes as above wrt using analyze_line and xstrtoul.

> +      }
> +      return ret;
> +    }
> +  }
> +
> +  reply_with_error("Minimum size not found. Check output format:\n%s", out);
> +  return -1;
> +}
> +
>  /* Takes optional arguments, consult optargs_bitmask. */
>  int
>  do_ntfsfix (const char *device, int clearbadsectors)
> diff --git a/generator/actions.ml b/generator/actions.ml
> index 274ef3f..0646a16 100644
> --- a/generator/actions.ml
> +++ b/generator/actions.ml
> @@ -12765,6 +12765,22 @@ Get the estimated minimum filesystem size of an ext2/3/4 filesystem in blocks.
> 
>  See also L<resize2fs(8)>." };
> 
> +  { defaults with
> +    name = "vfs_min_size"; added = (1, 31, 18);
> +    style = RInt64 "sizeinbytes", [Mountable "mountable"], [];
> +    proc_nr = Some 458;
> +    tests = [
> +      InitPartition, IfAvailable "ntfsprogs", TestRun(
> +        [["mkfs"; "ntfs"; "/dev/sda1"; ""; "NOARG"; ""; ""; "NOARG"];
> +         ["vfs_min_size"; "/dev/sda1"]]), [];
> +    ];
> +    shortdesc = "get minimum filesystem size";
> +    longdesc = "\
> +Get the minimum size of filesystem in bytes.
> +This is the minimum possible size for filesystem shrinking.
> +
> +See also L<ntfsresize(8)>." };
> +
>  ]
> 
>  (* Non-API meta-commands available only in guestfish.
> diff --git a/po/POTFILES b/po/POTFILES
> index cd2c437..d90772a 100644
> --- a/po/POTFILES
> +++ b/po/POTFILES
> @@ -49,6 +49,7 @@ daemon/file.c
>  daemon/fill.c
>  daemon/find.c
>  daemon/findfs.c
> +daemon/fs-min-size.c
>  daemon/fsck.c
>  daemon/fstrim.c
>  daemon/glob.c
> diff --git a/src/MAX_PROC_NR b/src/MAX_PROC_NR
> index de2a00c..c92ddb6 100644
> --- a/src/MAX_PROC_NR
> +++ b/src/MAX_PROC_NR
> @@ -1 +1 @@
> -457
> +458
> --

Thanks,
-- 
Pino Toscano

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