[Libguestfs] [PATCH] btrfs: Fix btrfs_subvolume_list on F18
Matthew Booth
mbooth at redhat.com
Thu Jan 24 14:43:18 UTC 2013
The output of btrfs subvolume list has changed in F18 to include generation,
which breaks the parsing in btrfs_subvolume_list. This change replaces sscanf
with a more robust regular expression. The new regular expression should also
handle the addition of future unexpected columns.
Fixes RHBZ#903620
---
daemon/Makefile.am | 6 ++-
daemon/btrfs.c | 156 ++++++++++++++++++++++++++++++++++-------------------
2 files changed, 105 insertions(+), 57 deletions(-)
diff --git a/daemon/Makefile.am b/daemon/Makefile.am
index a05771e..d70dbd7 100644
--- a/daemon/Makefile.am
+++ b/daemon/Makefile.am
@@ -197,14 +197,16 @@ guestfsd_LDADD = \
$(LIBSOCKET) \
$(LIB_CLOCK_GETTIME) \
$(LIBINTL) \
- $(SERVENT_LIB)
+ $(SERVENT_LIB) \
+ $(PCRE_LIBS)
guestfsd_CPPFLAGS = -I$(top_srcdir)/gnulib/lib -I$(top_builddir)/gnulib/lib
guestfsd_CFLAGS = \
$(WARN_CFLAGS) $(WERROR_CFLAGS) \
$(AUGEAS_CFLAGS) \
$(HIVEX_CFLAGS) \
- $(YAJL_CFLAGS)
+ $(YAJL_CFLAGS) \
+ $(PCRE_CFLAGS)
# Manual pages and HTML files for the website.
man_MANS = guestfsd.8
diff --git a/daemon/btrfs.c b/daemon/btrfs.c
index 8ecde01..f13d025 100644
--- a/daemon/btrfs.c
+++ b/daemon/btrfs.c
@@ -21,12 +21,14 @@
#include <stdio.h>
#include <stdlib.h>
#include <inttypes.h>
+#include <pcre.h>
#include <string.h>
#include <unistd.h>
#include "daemon.h"
#include "actions.h"
#include "optgroups.h"
+#include "xstrtol.h"
GUESTFSD_EXT_CMD(str_btrfs, btrfs);
GUESTFSD_EXT_CMD(str_btrfstune, btrfstune);
@@ -321,97 +323,141 @@ do_btrfs_subvolume_create (const char *dest)
guestfs_int_btrfssubvolume_list *
do_btrfs_subvolume_list (const char *fs)
{
- const size_t MAX_ARGS = 64;
- guestfs_int_btrfssubvolume_list *ret;
- char *fs_buf;
- const char *argv[MAX_ARGS];
- size_t i = 0;
- char *out, *err, **lines, *pos;
- size_t nr_subvolumes;
- int r;
-
- fs_buf = sysroot_path (fs);
- if (fs_buf == NULL) {
- reply_with_perror ("malloc");
- return NULL;
- }
+ char **lines;
- ADD_ARG (argv, i, str_btrfs);
- ADD_ARG (argv, i, "subvolume");
- ADD_ARG (argv, i, "list");
- ADD_ARG (argv, i, fs_buf);
- ADD_ARG (argv, i, NULL);
+ /* Execute 'btrfs subvolume list <fs>', and split the output into lines */
+ {
+ char *fs_buf = sysroot_path (fs);
+ if (fs_buf == NULL) {
+ reply_with_perror ("malloc");
+ return NULL;
+ }
- r = commandv (&out, &err, argv);
- free (fs_buf);
- if (r == -1) {
- reply_with_error ("%s: %s", fs, err);
+ size_t i = 0;
+ const size_t MAX_ARGS = 64;
+ const char *argv[MAX_ARGS];
+ ADD_ARG (argv, i, str_btrfs);
+ ADD_ARG (argv, i, "subvolume");
+ ADD_ARG (argv, i, "list");
+ ADD_ARG (argv, i, fs_buf);
+ ADD_ARG (argv, i, NULL);
+
+ char *out, *err;
+ int r = commandv (&out, &err, argv);
+ free (fs_buf);
+ if (r == -1) {
+ reply_with_error ("%s: %s", fs, err);
+ free (err);
+ return NULL;
+ }
free (err);
- return NULL;
- }
- free (err);
- lines = split_lines (out);
- free (out);
- if (!lines)
- return NULL;
+ lines = split_lines (out);
+ free (out); out = NULL;
+ if (!lines)
+ return NULL;
+ }
/* Output is:
*
- * ID 256 top level 5 path test1
- * ID 257 top level 5 path dir/test2
- * ID 258 top level 5 path test3
+ * ID 256 gen 30 top level 5 path test1
+ * ID 257 gen 30 top level 5 path dir/test2
+ * ID 258 gen 30 top level 5 path test3
*
- * "ID <n>" is the subvolume ID. "top level <n>" is the top level
- * subvolume ID. "path <str>" is the subvolume path, relative to
- * the top of the filesystem.
+ * "ID <n>" is the subvolume ID.
+ * "gen <n>" is the generation when the root was created or last
+ * updated.
+ * "top level <n>" is the top level subvolume ID.
+ * "path <str>" is the subvolume path, relative to the top of the
+ * filesystem.
+ *
+ * Note that the order that each of the above is fixed, but
+ * different versions of btrfs may display different sets of data.
+ * Specifically, older versions of btrfs do not display gen.
*/
- nr_subvolumes = count_strings (lines);
+
+ guestfs_int_btrfssubvolume_list *ret = NULL;
+ pcre *re = NULL;
+
+ size_t nr_subvolumes = count_strings (lines);
ret = malloc (sizeof *ret);
if (!ret) {
reply_with_perror ("malloc");
- free_stringslen (lines, nr_subvolumes);
- return NULL;
+ goto error;
}
+
ret->guestfs_int_btrfssubvolume_list_len = nr_subvolumes;
ret->guestfs_int_btrfssubvolume_list_val =
calloc (nr_subvolumes, sizeof (struct guestfs_int_btrfssubvolume));
if (ret->guestfs_int_btrfssubvolume_list_val == NULL) {
reply_with_perror ("malloc");
- free (ret);
- free_stringslen (lines, nr_subvolumes);
- return NULL;
+ goto error;
}
- for (i = 0; i < nr_subvolumes; ++i) {
+ const char *errptr;
+ int erroffset;
+ re = pcre_compile ("ID\\s+(\\d+).*\\s"
+ "top level\\s+(\\d+).*\\s"
+ "path\\s(.*)",
+ 0, &errptr, &erroffset, NULL);
+ if (re == NULL) {
+ reply_with_error ("pcre_compile (%i): %s", erroffset, errptr);
+ goto error;
+ }
+
+ for (size_t i = 0; i < nr_subvolumes; ++i) {
/* To avoid allocations, reuse the 'line' buffer to store the
* path. Thus we don't need to free 'line', since it will be
* freed by the calling (XDR) code.
*/
char *line = lines[i];
+ #define N_MATCHES 4
+ int ovector[N_MATCHES * 3];
- if (sscanf (line, "ID %" SCNu64 " top level %" SCNu64 " path ",
- &ret->guestfs_int_btrfssubvolume_list_val[i].btrfssubvolume_id,
- &ret->guestfs_int_btrfssubvolume_list_val[i].btrfssubvolume_top_level_id) != 2) {
+ if (pcre_exec (re, NULL, line, strlen (line), 0, 0,
+ ovector, N_MATCHES * 3) < 0)
+ #undef N_MATCHES
+ {
unexpected_output:
reply_with_error ("unexpected output from 'btrfs subvolume list' command: %s", line);
- free_stringslen (lines, nr_subvolumes);
- free (ret->guestfs_int_btrfssubvolume_list_val);
- free (ret);
- return NULL;
+ goto error;
}
- pos = strstr (line, " path ");
- if (pos == NULL)
+ struct guestfs_int_btrfssubvolume *this =
+ &ret->guestfs_int_btrfssubvolume_list_val[i];
+
+ #if __WORDSIZE == 64
+ #define XSTRTOU64 xstrtoul
+ #else
+ #define XSTRTOU64 xstrtoull
+ #endif
+
+ if (XSTRTOU64 (line + ovector[2], NULL, 10,
+ &this->btrfssubvolume_id, NULL) != LONGINT_OK)
+ goto unexpected_output;
+ if (XSTRTOU64 (line + ovector[4], NULL, 10,
+ &this->btrfssubvolume_top_level_id, NULL) != LONGINT_OK)
goto unexpected_output;
- pos += 6;
- memmove (line, pos, strlen (pos) + 1);
- ret->guestfs_int_btrfssubvolume_list_val[i].btrfssubvolume_path = line;
+ #undef XSTRTOU64
+
+ memmove (line, line + ovector[6], ovector[7] + 1);
+ this->btrfssubvolume_path = line;
}
+ free (lines);
+ pcre_free (re);
+
return ret;
+
+error:
+ free_stringslen (lines, nr_subvolumes);
+ if (ret) free (ret->guestfs_int_btrfssubvolume_list_val);
+ free (ret);
+ if (re) pcre_free (re);
+
+ return NULL;
}
int
--
1.8.1
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