From 9b705c104f2cde7106fdbe27d14bcf4be64df0ad Mon Sep 17 00:00:00 2001 From: Richard Jones Date: Thu, 22 Jul 2010 14:39:36 +0100 Subject: [PATCH] Revert "add_drive_ro adds readonly=on option if available." (RHBZ#617200). Adding the readonly=on option is not so clever. This causes qemu to present the disk as read-only to the guest. (The expected behaviour of snapshots=on,readonly=on was that it would open the disk O_RDONLY but present a writable disk to the guest). Since the guest sees a read-only disk, we are unable to do any recovery if a filesystem on the disk is inconsistent. This basically prevents most accesses to live disk images. What we really want is a qemu option which presents a writable disk to the guest, but only opens the disk on the host side with O_RDONLY, to alleviate the udev bug RHBZ#571714. This reverts commit 676462684e05dd8341dd695762dd99a87d8ec022. (cherry picked from commit 799d52be4f08f6c70c0e8ba1aa7367ba4cdd78c4) --- src/generator.ml | 4 +--- src/guestfs.c | 22 ++++------------------ 2 files changed, 5 insertions(+), 21 deletions(-) diff --git a/src/generator.ml b/src/generator.ml index 3ee4b8b..d199d74 100755 --- a/src/generator.ml +++ b/src/generator.ml @@ -551,15 +551,13 @@ handle is closed. We don't currently have any method to enable changes to be committed, although qemu can support this. This is equivalent to the qemu parameter -C<-drive file=filename,snapshot=on,readonly=on,if=...>. +C<-drive file=filename,snapshot=on,if=...>. C is set at compile time by the configuration option C<./configure --with-drive-if=...>. In the rare case where you might need to change this at run time, use C or C. -C is only added where qemu supports this option. - Note that this call checks for the existence of C. This stops you from specifying other types of drive which are supported by qemu such as C and C URLs. To specify those, use diff --git a/src/guestfs.c b/src/guestfs.c index 1439361..e7a5e66 100644 --- a/src/guestfs.c +++ b/src/guestfs.c @@ -836,6 +836,9 @@ int guestfs__add_drive_ro_with_if (guestfs_h *g, const char *filename, const char *drive_if) { + size_t len = strlen (filename) + 64; + char buf[len]; + if (strchr (filename, ',') != NULL) { error (g, _("filename cannot contain ',' (comma) character")); return -1; @@ -846,24 +849,7 @@ guestfs__add_drive_ro_with_if (guestfs_h *g, const char *filename, return -1; } - if (qemu_supports (g, NULL) == -1) - return -1; - - /* Only SCSI and virtio drivers support readonly mode. - * This is only supported as a QEMU feature since 2010/01. - */ - int supports_ro = 0; - if ((STREQ (drive_if, "scsi") || STREQ (drive_if, "virtio")) && - qemu_supports (g, "readonly=on")) - supports_ro = 1; - - size_t len = strlen (filename) + 100; - char buf[len]; - - snprintf (buf, len, "file=%s,snapshot=on,%sif=%s", - filename, - supports_ro ? "readonly=on," : "", - drive_if); + snprintf (buf, len, "file=%s,snapshot=on,if=%s", filename, drive_if); return guestfs__config (g, "-drive", buf); } -- 1.8.3.1