[PATCH 2/2 V3] mkfs.xfs: don't call blkid_get_topology on existing regular files

[Eric Sandeen <sandeen@xxxxxxxxxxx>]

If we encounter a target that's really a regular file,
even without "-d file..." on the cmdline, call
platform_findsizes() instead of blkid_get_topology to
try to discover the "sector size" via the fsgeom() call.

Otherwise mkfs.xfs will try to do direct IO with a default
512 sector size, and if the underlying file has different
DIO requirements, mkfs will fail.

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

V3: only call platform_findsizes if xi->disfile isn't set,
and our target is a regular file: i.e. only in the 
"mkfs.xfs <existing regular file>" case.

diff --git a/mkfs/xfs_mkfs.c b/mkfs/xfs_mkfs.c
index 188b6b3..c85258a 100644
--- a/mkfs/xfs_mkfs.c
+++ b/mkfs/xfs_mkfs.c
@@ -457,11 +457,30 @@ static void get_topology(
        int                     force_overwrite)
 {
        if (!xi->disfile) {
-               const char *dfile = xi->volname ? xi->volname : xi->dname;
+               char *dfile = xi->volname ? xi->volname : xi->dname;
+               struct stat statbuf;
 
-               blkid_get_topology(dfile, &ft->dsunit, &ft->dswidth,
-                                  &ft->lsectorsize, &ft->psectorsize,
-                                  force_overwrite);
+               /*
+                * If our target is a regular file, and xi->disfile isn't
+                * set (i.e. no "-d file" invocation), use platform_findsizes
+                * to try to obtain the underlying filesystem's requirements
+                * for direct IO; we'll set our sector size to that if possible.
+                */
+               if (!stat(dfile, &statbuf) && S_ISREG(statbuf.st_mode)) {
+                       int fd;
+                       long long dummy;
+
+                       fd = open(dfile, O_RDONLY);
+                       if (fd >= 0) {
+                               platform_findsizes(dfile, fd, &dummy,
+                                                  &ft->lsectorsize);
+                               close(fd);
+                       }
+               } else {
+                       blkid_get_topology(dfile, &ft->dsunit, &ft->dswidth,
+                                          &ft->lsectorsize, &ft->psectorsize,
+                                          force_overwrite);
+               }
        }
 
        if (xi->rtname && !xi->risfile) {