>From 26161a7a03edcad9cebf6908c052475765250ffb Mon Sep 17 00:00:00 2001 From: Richard Jones Date: Tue, 16 Mar 2010 20:06:54 +0000 Subject: [PATCH] add_drive_ro adds readonly=on option if available. Change the add_drive_ro call so it adds the readonly=on option if qemu supports that. This just means that qemu will not try to open the drive with O_RDWR, and should not otherwise change the behaviour of qemu or libguestfs. (In particular, writes to the read-only drive are still permitted, and are just discarded when the handle is closed). However it should alleviate RHBZ#571714 where udev was deciding to incorrectly relabel a device because we had opened the device for writing (even though we didn't actually write to it). --- src/generator.ml | 4 +++- src/guestfs.c | 21 ++++++++++++++++----- 2 files changed, 19 insertions(+), 6 deletions(-) diff --git a/src/generator.ml b/src/generator.ml index 486b9d8..38e0706 100755 --- a/src/generator.ml +++ b/src/generator.ml @@ -544,13 +544,15 @@ 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,if=...>. +C<-drive file=filename,snapshot=on,readonly=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 2ba062c..85f2307 100644 --- a/src/guestfs.c +++ b/src/guestfs.c @@ -91,6 +91,7 @@ static int recv_from_daemon (guestfs_h *g, uint32_t *size_rtn, void **buf_rtn); static int accept_from_daemon (guestfs_h *g); static int check_peer_euid (guestfs_h *g, int sock, uid_t *rtn); static void close_handles (void); +static int qemu_supports (guestfs_h *g, const char *option); #define UNIX_PATH_MAX 108 @@ -791,9 +792,6 @@ 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; @@ -804,7 +802,21 @@ guestfs__add_drive_ro_with_if (guestfs_h *g, const char *filename, return -1; } - snprintf (buf, len, "file=%s,snapshot=on,if=%s", filename, drive_if); + /* 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); return guestfs__config (g, "-drive", buf); } @@ -871,7 +883,6 @@ dir_contains_files (const char *dir, ...) static void print_timestamped_message (guestfs_h *g, const char *fs, ...); static int build_supermin_appliance (guestfs_h *g, const char *path, char **kernel, char **initrd); static int test_qemu (guestfs_h *g); -static int qemu_supports (guestfs_h *g, const char *option); static int is_openable (guestfs_h *g, const char *path, int flags); static void print_cmdline (guestfs_h *g); -- 1.6.5.2