On Sat, 2010-08-21 at 16:01 -0700, Nicholas A. Bellinger wrote:
> From: Nicholas Bellinger <nab@xxxxxxxxxxxxxxx>
>
> Greetings hch, tomo and Co,
>
> This patch changes the Linux BSG backstore detect logic in hdev_open()
> in order to determine when to actually set 'bs->sg = BDS_BSG;' by obtaining
> the BSG major from a SysFS attribute in /sys/class/bsg/$H:C:T:L/dev,
> instead of the original hardcoded 254 major check.
>
> This patch has been tested with Linux KVM guest v2.6.26 using the megasas
> HBA emulation SGL passthrough from a TCM_Loop IBLOCK backstore running on
> v2.6.35 x86_64.
>
> Thanks to Mark Harvey for initially contributing code for doing this with
> tgt.git/usr/bs_sg.c!
>
> Thanks!
>
> Signed-off-by: Nicholas A. Bellinger <nab@xxxxxxxxxxxxxxx>
> ---
> block/raw-posix.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++----
> 1 files changed, 47 insertions(+), 4 deletions(-)
>
> diff --git a/block/raw-posix.c b/block/raw-posix.c
> index e7afc4a..487e7f0 100644
> +++ b/block/raw-posix.c
> @@ -842,7 +842,10 @@ static int hdev_open(BlockDriverState *bs, const char *filename, int flags)
> {
> BDRVRawState *s = bs->opaque;
> #if defined(__linux__)
> - struct stat st;
> + struct stat st, st2;
> + FILE *file;
> + char major[8], dev[64], path[128], *p, *buf;
> + int ch, i;
> #endif
>
> #ifdef CONFIG_COCOA
> @@ -881,11 +884,51 @@ static int hdev_open(BlockDriverState *bs, const char *filename, int flags)
> if (S_ISCHR(st.st_mode)) {
> if (major(st.st_rdev) == SCSI_GENERIC_MAJOR) {
> bs->sg = BDS_SCSI_GENERIC;
> - } else if (major(st.st_rdev) == 254) {
> - /* This is not yet defined in include/linux/major.h.. */
> - bs->sg = BDS_BSG;
> + } else { /* Extract major for BSG backstore usage */
> + memset(major, 0, 8);
> + memset(dev, 0, 64);
> + memset(path, 0, 128);
> +
> + buf = strdup(filename);
> + if (!(buf))
> + goto out;
Ugh, one quick followup on this to address missing free(buf) calls from
the usage of buf = strdup(filename).
http://git.kernel.org/?p=virt/kvm/nab/qemu-kvm.git;a=commitdiff;h=9cc774b1766c07065dee4637febe9f7d9237ff7e
Thanks,
--nab
> + /*
> + * Locate the device name from the path, we are interested
> + * in the last strsep() token..
> + */
> + while ((p = strsep(&buf, "/")))
> + snprintf(dev, 64, "%s", p);
> + /*
> + * Check to sure the sysfs entry exists before calling open
> + */
> + snprintf(path, 128, "/sys/class/bsg/%s/dev", dev);
> + if (stat(path, &st2) < 0)
> + goto out;
> +
> + file = fopen(path, "r");
> + if (!(file)) {
> + printf("fopen() failed for BSG sysfs path: %s\n", path);
> + goto out;
> + }
> + ch = fgetc(file);
> + for (i = 0; i < 7; i++) {
> + if (ch == ':') {
> + major[i] = '\0';
> + break;
> + }
> + major[i] = ch;
> + ch = fgetc(file);
> + }
> + fclose(file);
> + /*
> + * If the major returned by /sys/class/bsg/$H:C:T:L/dev matches
> + * stat(), then we signal BDS_BSG usage.
> + */
> + if (major(st.st_rdev) == atoi(major))
> + bs->sg = BDS_BSG;
> }
> }
> +out:
> #endif
>
> return raw_open_common(bs, filename, flags, 0);
> --
> 1.5.6.5
>
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