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losetup: don't require 512-byte aligned offsets 

Kernel aligns the device size, but the offset where the device starts
is not required to be aligned.

 # losetup --offset 32 -f file.img

is just fine, the final size of the look device will be (in sectors)

  (backing_file_size - offset) >> 9

so we have to do the same in userspace when we check for successful
set capacity ioctl.

Signed-off-by: Karel Zak <kzak@redhat.com>
This commit is contained in:
Karel Zak 2013-10-01 15:52:11 +02:00
parent c1d26ddbe7
commit a7d5202b5e
2 changed files with 7 additions and 5 deletions
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6
lib/loopdev.c
View File

@ -1129,6 +1129,12 @@ static int loopcxt_check_size(struct loopdev_cxt *lc, int file_fd)
return -errno;
}
/* It's block device, so, align to 512-byte sectors */
if (expected_size % 512) {
DBG(lc, loopdev_debug("expected size misaligned to 512-byte sectors"));
expected_size = (expected_size >> 9) << 9;
}
if (expected_size != size) {
DBG(lc, loopdev_debug("warning: loopdev and expected "
"size dismatch (%ju/%ju)",

6
sys-utils/losetup.c
View File

@ -673,11 +673,7 @@ int main(int argc, char **argv)
/* errors */
errpre = hasdev && loopcxt_get_fd(&lc) < 0 ?
loopcxt_get_device(&lc) : file;
if (errno == ERANGE && offset && offset % 512)
warnx(_("%s: failed to set up loop device, "
"offset is not 512-byte aligned."), errpre);
else
warn(_("%s: failed to set up loop device"), errpre);
warn(_("%s: failed to set up loop device"), errpre);
break;
} while (hasdev == 0);