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Message-ID: <F792CF86EFE20D4AB8064279AFBA51C610587577@HKNPRD3002MB017.064d.mgd.msft.net>
Date: Tue, 4 Nov 2014 02:16:50 +0000
From: Dexuan Cui <decui@...rosoft.com>
To: "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"driverdev-devel@...uxdriverproject.org"
<driverdev-devel@...uxdriverproject.org>,
"olaf@...fle.de" <olaf@...fle.de>,
"apw@...onical.com" <apw@...onical.com>,
"jasowang@...hat.com" <jasowang@...hat.com>
Subject: RE: [PATCH v3 RESEND] Tools: hv: vssdaemon: ignore the EBUSY on
multiple freezing the same partition
> -----Original Message-----
> From: devel [mailto:driverdev-devel-bounces@...uxdriverproject.org] On
> Behalf Of Dexuan Cui
> Sent: Tuesday, October 21, 2014 17:56 PM
> To: gregkh@...uxfoundation.org; linux-kernel@...r.kernel.org; driverdev-
> devel@...uxdriverproject.org; olaf@...fle.de; apw@...onical.com;
> jasowang@...hat.com
> Cc: Haiyang Zhang
> Subject: [PATCH v3 RESEND] Tools: hv: vssdaemon: ignore the EBUSY on
> multiple freezing the same partition
>
> If a partition appears mounted more than once in /proc/mounts,
> vss_do_freeze()
> succeeds only for the first time and gets EBUSY (on freeze) or EINVAL (on
> thaw) for the second time. The patch ignores these to make the backup
> feature
> work.
>
> Also improved the error handling in case a freeze operation fails.
>
> Signed-off-by: Dexuan Cui <decui@...rosoft.com>
> Reviewed-by: K. Y. Srinivasan <kys@...rosoft.com>
> ---
>
> v2: Add "errno = 0;" before the ioctl()
> (Unnecessary and removed now since we remove syslog() in vss_do_freeze()
> in v3)
>
> v3: Remove the unsafe syslog() in vss_do_freeze(): that could write the disk.
> Thaw the filesystems in case the freezing operation fails.
> In main(), add syslog() when we check the return value of vss_operate().
>
> [Oct 21, 2014] This is just a RESEND since the previous one I sent about a
> month
> ago seems neglected. :-(
>
> tools/hv/hv_vss_daemon.c | 48
> ++++++++++++++++++++++++++++++++++++++++--------
> 1 file changed, 40 insertions(+), 8 deletions(-)
>
> diff --git a/tools/hv/hv_vss_daemon.c b/tools/hv/hv_vss_daemon.c
> index 6a213b8..1db9430 100644
> --- a/tools/hv/hv_vss_daemon.c
> +++ b/tools/hv/hv_vss_daemon.c
> @@ -44,21 +44,39 @@ static struct sockaddr_nl addr;
> #endif
>
>
> -static int vss_do_freeze(char *dir, unsigned int cmd, char *fs_op)
> +/* Don't use syslog() in the function since that can cause write to disk */
> +static int vss_do_freeze(char *dir, unsigned int cmd)
> {
> int ret, fd = open(dir, O_RDONLY);
>
> if (fd < 0)
> return 1;
> +
> ret = ioctl(fd, cmd, 0);
> - syslog(LOG_INFO, "VSS: %s of %s: %s\n", fs_op, dir, strerror(errno));
> +
> + /*
> + * If a partition is mounted more than once, only the first
> + * FREEZE/THAW can succeed and the later ones will get
> + * EBUSY/EINVAL respectively: there could be 2 cases:
> + * 1) a user may mount the same partition to differnt directories
> + * by mistake or on purpose;
> + * 2) The subvolume of btrfs appears to have the same partition
> + * mounted more than once.
> + */
> + if (ret) {
> + if ((cmd == FIFREEZE && errno == EBUSY) ||
> + (cmd == FITHAW && errno == EINVAL)) {
> + close(fd);
> + return 0;
> + }
> + }
> +
> close(fd);
> return !!ret;
> }
>
> static int vss_operate(int operation)
> {
> - char *fs_op;
> char match[] = "/dev/";
> FILE *mounts;
> struct mntent *ent;
> @@ -68,11 +86,9 @@ static int vss_operate(int operation)
> switch (operation) {
> case VSS_OP_FREEZE:
> cmd = FIFREEZE;
> - fs_op = "freeze";
> break;
> case VSS_OP_THAW:
> cmd = FITHAW;
> - fs_op = "thaw";
> break;
> default:
> return -1;
> @@ -93,15 +109,23 @@ static int vss_operate(int operation)
> root_seen = 1;
> continue;
> }
> - error |= vss_do_freeze(ent->mnt_dir, cmd, fs_op);
> + error |= vss_do_freeze(ent->mnt_dir, cmd);
> + if (error && operation == VSS_OP_FREEZE)
> + goto err;
> }
> endmntent(mounts);
>
> if (root_seen) {
> - error |= vss_do_freeze("/", cmd, fs_op);
> + error |= vss_do_freeze("/", cmd);
> + if (error && operation == VSS_OP_FREEZE)
> + goto err;
> }
>
> return error;
> +err:
> + endmntent(mounts);
> + vss_operate(VSS_OP_THAW);
> + return error;
> }
>
> static int netlink_send(int fd, struct cn_msg *msg)
> @@ -249,8 +273,16 @@ int main(void)
> case VSS_OP_FREEZE:
> case VSS_OP_THAW:
> error = vss_operate(op);
> - if (error)
> + syslog(LOG_INFO, "VSS: op=%s: %s\n",
> + op == VSS_OP_FREEZE ? "FREEZE" : "THAW",
> + error ? "failed" : "succeeded");
> +
> + if (error) {
> error = HV_E_FAIL;
> + syslog(LOG_ERR, "op=%d failed!", op);
> + syslog(LOG_ERR, "report it with these files:");
> + syslog(LOG_ERR, "/etc/fstab and
> /proc/mounts");
> + }
> break;
> default:
> syslog(LOG_ERR, "Illegal op:%d\n", op);
> --
> 1.9.1
Hi Greg,
ping.
(I saw you replying in the lists 3 minutes ago. :-)
Thanks,
-- Dexuan
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