From 293714c0d157ae04d08bb587e800c70f05cc4a29 Mon Sep 17 00:00:00 2001 From: Jeff Mahoney Date: Tue, 9 Apr 2013 14:32:50 +0200 Subject: loopdev: sync capacity after setting it I recently tried to mount an hfsplus file system from an image file with a partition table by using the loop offset and sizelimit options to specify the location of the file system. hfsplus stores some metadata at a set offset from the end of the partition, so it's sensitive to the device size reported by the kernel. It worked with this: But failed with this: /dev/loop0: [0089]:2 (), offset 32768, sizelimit 102400000 /dev/loop1: [0089]:2 (), offset 32768, sizelimit 102400000 /proc/partitions shows the correct number of blocks to match the sizelimit. But if I set a breakpoint in mount before the mount syscall, I could see: 102400000 102432768 The kernel loop driver will set the gendisk capacity of the device at LOOP_SET_STATUS64 but won't sync it to the block device until one of two conditions are met: All open file descriptors referring to the device are closed (and it will sync when re-opened) or if the LOOP_SET_CAPACITY ioctl is called to sync it. Since mount opens the device and passes it directly to the mount syscall after LOOP_SET_STATUS64 without closing and reopening it, the sizelimit argument is effectively ignroed. The capacity needs to be synced immediately for it to work as expected. This patch adds the LOOP_SET_CAPACITY call to loopctx_setup_device since the device isn't yet released to the user, so it's safe to sync the capacity immediately. [kzak@redhat.com: - port to the current git HEAD, - use uint64_t] Signed-off-by: Jeff Mahoney Signed-off-by: Karel Zak --- sys-utils/losetup.c | 19 ++++--------------- 1 file changed, 4 insertions(+), 15 deletions(-) (limited to 'sys-utils/losetup.c') diff --git a/sys-utils/losetup.c b/sys-utils/losetup.c index 8f3614e1f..ccf120e9f 100644 --- a/sys-utils/losetup.c +++ b/sys-utils/losetup.c @@ -183,20 +183,6 @@ static int show_all_loops(struct loopdev_cxt *lc, const char *file, return 0; } -static int set_capacity(struct loopdev_cxt *lc) -{ - int fd = loopcxt_get_fd(lc); - - if (fd < 0) - warn(_("cannot open %s"), loopcxt_get_device(lc)); - else if (ioctl(fd, LOOP_SET_CAPACITY) != 0) - warnx(_("%s: set capacity failed"), loopcxt_get_device(lc)); - else - return 0; - - return -1; -} - static int delete_loop(struct loopdev_cxt *lc) { if (loopcxt_delete_device(lc)) @@ -685,7 +671,10 @@ int main(int argc, char **argv) warn(_("%s"), loopcxt_get_device(&lc)); break; case A_SET_CAPACITY: - res = set_capacity(&lc); + res = loopcxt_set_capacity(&lc); + if (res) + warn(_("%s: set capacity failed"), + loopcxt_get_device(&lc)); break; default: usage(stderr); -- cgit v1.2.3-55-g7522