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

[Eric Sandeen <sandeen@sandeen.net>]

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@redhat.com>
---

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) {


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