[PATCH 2/2] libxfs: remove ustat() use, factor mount checks into helper function

[Eric Sandeen <sandeen@xxxxxxxxxxx>]

ustat() has been deprecated for a very long time, and newer
architectures (aarch64, for one) have not implemented it.
If called, it always returns false, so we can no longer use
it to determine a device's mounted status.

We already have another mechanism for determining the mounted
status of a device in platform_check_iswritable; it iterates
over getmntent looking for the device, and checks its mount
options.  We can do the same thing to check for a simple mount,
and not caring about the "ro" mount option.

Because the loop is essentially the same, factor it into a
helper which accepts a VERBOSE flag to print info if the device
is found in the checked-for state, and a WRITABLE flag which
only checks specifically for a mounted and /writable/ device.

Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx>
---

Dave, up to you if you want to take all this in lieu of the
fixed-up patch from Felix, or if you'd like me to rebase this
once you have merged that patch.  Happy to do that if you'd like -
now that I think about it, that may be the cleaner progression
of changes.

Thanks,
-Eric

diff --git a/libxfs/linux.c b/libxfs/linux.c
index 67b615b..fad9a4a 100644
--- a/libxfs/linux.c
+++ b/libxfs/linux.c
@@ -48,14 +48,24 @@ static int max_block_alignment;
 
 #define PROC_MOUNTED   "/proc/mounts"
 
-int
-platform_check_ismounted(char *name, char *block, struct stat64 *s, int 
verbose)
+/*
+ * Check if the filesystem is mounted.  Be verbose if asked, and
+ * optionally restrict check to writable mounts.
+ */
+#define        CHECK_MOUNT_VERBOSE     0x1
+#define        CHECK_MOUNT_WRITABLE    0x2
+
+static int
+platform_check_mount(char *name, char *block, struct stat64 *s, int flags)
 {
-       /* Pad ust; pre-2.6.28 linux copies out too much in 32bit compat mode */
-       struct ustat    ust[2];
        struct stat64   st;
+       struct stat64   mst;
+       FILE            *f;
+       struct mntent   *mnt;
+       char            mounts[MAXPATHLEN];
 
        if (!s) {
+               /* If either fails we are neither mounted nor writable */
                if (stat64(block, &st) < 0)
                        return 0;
                if ((st.st_mode & S_IFMT) != S_IFBLK)
@@ -63,47 +73,64 @@ platform_check_ismounted(char *name, char *block, struct 
stat64 *s, int verbose)
                s = &st;
        }
 
-       if (ustat(s->st_rdev, ust) >= 0) {
-               if (verbose)
-                       fprintf(stderr,
-                               _("%s: %s contains a mounted filesystem\n"),
-                               progname, name);
-               return 1;
-       }
-       return 0;
-}
-
-int
-platform_check_iswritable(char *name, char *block, struct stat64 *s)
-{
-       FILE            *f;
-       struct stat64   mst;
-       struct mntent   *mnt;
-       char            mounts[MAXPATHLEN];
-
        strcpy(mounts, (!access(PROC_MOUNTED, R_OK)) ? PROC_MOUNTED : MOUNTED);
        if ((f = setmntent(mounts, "r")) == NULL) {
+               /* Unexpected failure, warn unconditionally */
                fprintf(stderr, _("%s: %s contains a possibly writable, "
                                "mounted filesystem\n"), progname, name);
-                       return 1;
+               return 1;
        }
+
        while ((mnt = getmntent(f)) != NULL) {
                if (stat64(mnt->mnt_fsname, &mst) < 0)
                        continue;
                if ((mst.st_mode & S_IFMT) != S_IFBLK)
                        continue;
-               if (mst.st_rdev == s->st_rdev
-                   && hasmntopt(mnt, MNTOPT_RO) != NULL)
-                       break;
+               if (mst.st_rdev == s->st_rdev) {
+                       /* Found our device */
+                       if (!(flags & CHECK_MOUNT_WRITABLE) ||
+                           !hasmntopt(mnt, MNTOPT_RO))
+                               break;
+               }
        }
        endmntent(f);
 
-       if (mnt == NULL) {
-               fprintf(stderr, _("%s: %s contains a mounted and writable "
-                               "filesystem\n"), progname, name);
-               return 1;
+       /* No mounts contained the condition we were looking for */
+       if (mnt == NULL)
+               return 0;
+
+       if (flags & CHECK_MOUNT_VERBOSE) {
+               if (flags & CHECK_MOUNT_WRITABLE) {
+                       fprintf(stderr,
+_("%s: %s contains a mounted and writable filesystem\n"),
+                               progname, name);
+               } else {
+                       fprintf(stderr,
+_("%s: %s contains a mounted filesystem\n"),
+                               progname, name);
+               }
        }
-       return 0;
+
+       return 1;
+}
+
+int
+platform_check_ismounted(char *name, char *block, struct stat64 *s, int 
verbose)
+{
+       int flags;
+
+       flags = verbose ? CHECK_MOUNT_VERBOSE : 0;
+       return platform_check_mount(name, block, s, flags);
+}
+
+int
+platform_check_iswritable(char *name, char *block, struct stat64 *s)
+{
+       int flags;
+
+       /* Writable checks are always verbose */
+       flags = CHECK_MOUNT_WRITABLE | CHECK_MOUNT_VERBOSE;
+       return platform_check_mount(name, block, s, flags);
 }
 
 int