From 31daa90b6eee2e3544a8e4ae92687d4cf01675d1 Mon Sep 17 00:00:00 2001 From: Brian Foster Date: Tue, 7 Apr 2015 10:04:11 +1000 Subject: [PATCH] mkfs: don't zero old superblocks if file was truncated If the force overwrite option is passed to mkfs, we attempt to zero old superblock metadata on the mkfs target. We attempt to read the primary superblock to identify the secondary superblocks. If the mkfs target is a regular file, it is truncated on open and the secondary superblock zeroing operation returns a spurious and incorrect error message due to a 0-byte read: $ mkfs.xfs -f -d file=1,name=xfs.fs,size=32m ... existing superblock read failed: Inappropriate ioctl for device Fix the error reporting in zero_old_xfs_structures() to only print an error string if the pread() call returns an error. Warn the user if the read doesn't match the sector size. Finally, detect the case where we know we've already truncated a regular file and skip the sb zeroing. Reported-by: Alexander Tsvetkov Signed-off-by: Brian Foster Reviewed-by: Dave Chinner Signed-off-by: Dave Chinner --- mkfs/xfs_mkfs.c | 18 +++++++++++++++--- 1 file changed, 15 insertions(+), 3 deletions(-) diff --git a/mkfs/xfs_mkfs.c b/mkfs/xfs_mkfs.c index 484e7a858..5084d7555 100644 --- a/mkfs/xfs_mkfs.c +++ b/mkfs/xfs_mkfs.c @@ -817,6 +817,13 @@ zero_old_xfs_structures( __uint32_t bsize; int i; xfs_off_t off; + int tmp; + + /* + * We open regular files with O_TRUNC|O_CREAT. Nothing to do here... + */ + if (xi->disfile && xi->dcreat) + return; /* * read in existing filesystem superblock, use its geometry @@ -830,11 +837,16 @@ zero_old_xfs_structures( } memset(buf, 0, new_sb->sb_sectsize); - if (pread(xi->dfd, buf, new_sb->sb_sectsize, 0) != new_sb->sb_sectsize) { + tmp = pread(xi->dfd, buf, new_sb->sb_sectsize, 0); + if (tmp < 0) { fprintf(stderr, _("existing superblock read failed: %s\n"), strerror(errno)); - free(buf); - return; + goto done; + } + if (tmp != new_sb->sb_sectsize) { + fprintf(stderr, + _("warning: could not read existing superblock, skip zeroing\n")); + goto done; } libxfs_sb_from_disk(&sb, buf); -- 2.50.1