Libguestfs - Oct 2015 - [PATCH] New API: resize2fs_P

Added support for getting ext2/3/4 filesystem minimum size.
This is needed primarily for shrinking images.

---
 daemon/ext2.c        | 35 +++++++++++++++++++++++++++++++++++
 generator/actions.ml | 10 ++++++++++
 src/MAX_PROC_NR      |  2 +-
 3 files changed, 46 insertions(+), 1 deletion(-)

diff --git a/daemon/ext2.c b/daemon/ext2.c
index ebaf0f0..3dae40f 100644
--- a/daemon/ext2.c
+++ b/daemon/ext2.c
@@ -279,6 +279,41 @@ do_resize2fs_M (const char *device)
   return 0;
 }

+int64_t
+do_resize2fs_P (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;
+  char pattern[] = "Estimated minimum size of the filesystem: ";
+
+  r = command (&out, &err, str_resize2fs, "-P", device,
NULL);
+  if (r == -1) {
+    reply_with_error ("%s", err);
+    return -1;
+  }
+
+  lines = split_lines (out);
+  if (lines == NULL)
+    return -1;
+
+  for (i = 0; lines[i] != NULL; ++i) {
+    if (verbose)
+      fprintf (stderr, "resize2fs-P: lines[%zu] =
\"%s\"\n", i, lines[i]);
+
+    if ((p = strstr (lines[i], pattern))) {
+      if (sscanf (p + strlen(pattern), "%" SCNu64, &ret) != 1)
+        return -1;
+      return ret;
+    }
+  }
+
+  return -1;
+}
+
 /* Takes optional arguments, consult optargs_bitmask. */
 int
 do_e2fsck (const char *device,
diff --git a/generator/actions.ml b/generator/actions.ml
index a76b466..7e2bfac 100644
--- a/generator/actions.ml
+++ b/generator/actions.ml
@@ -12751,6 +12751,16 @@ Only some filesystem types support setting UUIDs.

 To read the UUID on a filesystem, call C<guestfs_vfs_uuid>." };

+  { defaults with
+    name = "resize2fs_P"; added = (1, 31, 17);
+    style = RInt64 "sizeinblocks", [Device "device"], [];
+    proc_nr = Some 457;
+    shortdesc = "get minimum filesystem size in blocks";
+    longdesc = "\
+Get the minimum filesystem size in blocks.
+
+See also L<resize2fs(8)>." };
+
 ]

 (* Non-API meta-commands available only in guestfish.
diff --git a/src/MAX_PROC_NR b/src/MAX_PROC_NR
index 8d38505..de2a00c 100644
--- a/src/MAX_PROC_NR
+++ b/src/MAX_PROC_NR
@@ -1 +1 @@
-456
+457
--
1.8.3.1

On Tue, Oct 13, 2015 at 06:26:25PM +0300, Maxim Perevedentsev
wrote:
> Added support for getting ext2/3/4 filesystem minimum size.
> This is needed primarily for shrinking images.
> 
> ---
>  daemon/ext2.c        | 35 +++++++++++++++++++++++++++++++++++
>  generator/actions.ml | 10 ++++++++++
>  src/MAX_PROC_NR      |  2 +-
>  3 files changed, 46 insertions(+), 1 deletion(-)
> 
> diff --git a/daemon/ext2.c b/daemon/ext2.c
> index ebaf0f0..3dae40f 100644
> --- a/daemon/ext2.c
> +++ b/daemon/ext2.c
> @@ -279,6 +279,41 @@ do_resize2fs_M (const char *device)
>    return 0;
>  }
> 
> +int64_t
> +do_resize2fs_P (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;
> +  char pattern[] = "Estimated minimum size of the filesystem: ";
> +
> +  r = command (&out, &err, str_resize2fs, "-P", device,
NULL);
> +  if (r == -1) {
> +    reply_with_error ("%s", err);
> +    return -1;
> +  }
> +
> +  lines = split_lines (out);
> +  if (lines == NULL)
> +    return -1;
> +
> +  for (i = 0; lines[i] != NULL; ++i) {
> +    if (verbose)
> +      fprintf (stderr, "resize2fs-P: lines[%zu] =
\"%s\"\n", i, lines[i]);
> +
> +    if ((p = strstr (lines[i], pattern))) {
> +      if (sscanf (p + strlen(pattern), "%" SCNu64, &ret) !=
1)
> +        return -1;
> +      return ret;
> +    }
> +  }
> +
> +  return -1;
> +}
> +
>  /* Takes optional arguments, consult optargs_bitmask. */
>  int
>  do_e2fsck (const char *device,
> diff --git a/generator/actions.ml b/generator/actions.ml
> index a76b466..7e2bfac 100644
> --- a/generator/actions.ml
> +++ b/generator/actions.ml
> @@ -12751,6 +12751,16 @@ Only some filesystem types support setting UUIDs.
> 
>  To read the UUID on a filesystem, call C<guestfs_vfs_uuid>." };
> 
> +  { defaults with
> +    name = "resize2fs_P"; added = (1, 31, 17);
> +    style = RInt64 "sizeinblocks", [Device "device"],
[];
> +    proc_nr = Some 457;
> +    shortdesc = "get minimum filesystem size in blocks";
> +    longdesc = "\
> +Get the minimum filesystem size in blocks.
> +
> +See also L<resize2fs(8)>." };
> +
>  ]
> 
>  (* Non-API meta-commands available only in guestfish.
> diff --git a/src/MAX_PROC_NR b/src/MAX_PROC_NR
> index 8d38505..de2a00c 100644
> --- a/src/MAX_PROC_NR
> +++ b/src/MAX_PROC_NR
> @@ -1 +1 @@
> -456
> +457
Looks fine to me.  Pino: any comment?

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-builder quickly builds VMs from scratch
http://libguestfs.org/virt-builder.1.html

On Tue, Oct 13, 2015 at 11:14:29PM +0100, Richard W.M. Jones
wrote:
> > +    if ((p = strstr (lines[i], pattern))) {
> > +      if (sscanf (p + strlen(pattern), "%" SCNu64,
&ret) != 1)
Actually this fails to compile:

ext2.c: In function 'do_resize2fs_P':
ext2.c:308:40: error: format '%lu' expects argument of type 'long
unsigned int *', but argument 3 has type 'int64_t * {aka long int
*}' [-Werror=format=]
       if (sscanf (p + strlen(pattern), "%" SCNu64, &ret) != 1)

It'd be good to have a test as well, ie. a tests = ... section
in generator/actions.ml.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
Fedora Windows cross-compiler. Compile Windows programs, test, and
build Windows installers. Over 100 libraries supported.
http://fedoraproject.org/wiki/MinGW

On Tue, Oct 13, 2015 at 06:26:25PM +0300, Maxim Perevedentsev wrote:

Another couple of things ...
> +  char pattern[] = "Estimated minimum size of the filesystem: ";
This should be 'const char *pattern'.
> +    if ((p = strstr (lines[i], pattern))) {
> +      if (sscanf (p + strlen(pattern), "%" SCNu64, &ret) !=
1)
> +        return -1;
> +      return ret;
There's a case for multiplying the return size by the block size of
the filesystem, thus returning the size in bytes.  It might make the
API easier to use.  Not sure how hard that is, or whether it actually
makes the API easier to use.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-df lists disk usage of guests without needing to install any
software inside the virtual machine.  Supports Linux and Windows.
http://people.redhat.com/~rjones/virt-df/

> There's a case for multiplying the return size by the block size of
> the filesystem, thus returning the size in bytes.  It might make the
> API easier to use.  Not sure how hard that is, or whether it actually
> makes the API easier to use.
>
> Rich.
This multiplication may confuse users who got used to "normal"
resize2fs
-P behavior (blocks) due to the name of API command.
I'm going to implement similar functionality for other filesystems 
(ntfs, btrfs, xfs).
I think we should preserve original command's behavior (well-documented, 
obviously!) and leave the conversion between blocks, megabytes, etc to user.
Maybe (later) we could implement aggregated call (getMinFsSizeInBytes()) 
to perform all this conversions.

-- 
Your sincerely,
Maxim Perevedentsev