Blame SOURCES/0001-Tools-hv-vss-fix-loop-device-detection.patch

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From 60c1606cbb7cc86f963a202c156e56ccdf1b57d9 Mon Sep 17 00:00:00 2001
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From: Vitaly Kuznetsov <vkuznets@redhat.com>
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Date: Tue, 5 Jun 2018 13:37:56 -0700
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Subject: [PATCH] Tools: hv: vss: fix loop device detection
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Commit ea81fdf0981d ("Tools: hv: vss: Skip freezing filesystems backed by
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loop") added skip for filesystems backed by loop device. However, it seems
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the detection of such cases is incomplete.
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It was found that with 'devicemapper' storage driver docker creates the
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following chain:
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NAME					MAJ:MIN
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loop0					7:0
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..docker-8:4-8473394-pool		253:0
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  ..docker-8:4-8473394-eac...		253:1
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so when we're looking at the mounted device we see major '253' and not '7'.
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Solve the issue by walking /sys/dev/block/*/slaves chain and checking if
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there's a loop device somewhere.
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Other than that, don't skip mountpoints silently when stat() fails. In case
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e.g. SELinux is failing stat we don't want to skip freezing everything
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without letting user know about the failure.
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Fixes: ea81fdf0981d ("Tools: hv: vss: Skip freezing filesystems backed by loop")
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Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
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Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
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---
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 tools/hv/hv_vss_daemon.c | 65 +++++++++++++++++++++++++++++++++++++++++++++---
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 1 file changed, 61 insertions(+), 4 deletions(-)
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diff --git a/tools/hv/hv_vss_daemon.c b/tools/hv/hv_vss_daemon.c
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index 34031a297f02..b13300172762 100644
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--- a/tools/hv/hv_vss_daemon.c
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+++ b/tools/hv/hv_vss_daemon.c
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@@ -36,6 +36,8 @@
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 #include <linux hyperv.h="">
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 #include <syslog.h>
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 #include <getopt.h>
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+#include <stdbool.h>
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+#include <dirent.h>
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 /* Don't use syslog() in the function since that can cause write to disk */
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 static int vss_do_freeze(char *dir, unsigned int cmd)
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@@ -68,6 +70,55 @@ static int vss_do_freeze(char *dir, unsigned int cmd)
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 	return !!ret;
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 }
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+static bool is_dev_loop(const char *blkname)
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+{
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+	char *buffer;
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+	DIR *dir;
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+	struct dirent *entry;
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+	bool ret = false;
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+
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+	buffer = malloc(PATH_MAX);
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+	if (!buffer) {
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+		syslog(LOG_ERR, "Can't allocate memory!");
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+		exit(1);
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+	}
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+
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+	snprintf(buffer, PATH_MAX, "%s/loop", blkname);
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+	if (!access(buffer, R_OK | X_OK)) {
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+		ret = true;
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+		goto free_buffer;
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+	} else if (errno != ENOENT) {
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+		syslog(LOG_ERR, "Can't access: %s; error:%d %s!",
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+		       buffer, errno, strerror(errno));
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+	}
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+
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+	snprintf(buffer, PATH_MAX, "%s/slaves", blkname);
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+	dir = opendir(buffer);
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+	if (!dir) {
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+		if (errno != ENOENT)
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+			syslog(LOG_ERR, "Can't opendir: %s; error:%d %s!",
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+			       buffer, errno, strerror(errno));
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+		goto free_buffer;
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+	}
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+
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+	while ((entry = readdir(dir)) != NULL) {
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+		if (strcmp(entry->d_name, ".") == 0 ||
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+		    strcmp(entry->d_name, "..") == 0)
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+			continue;
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+
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+		snprintf(buffer, PATH_MAX, "%s/slaves/%s", blkname,
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+			 entry->d_name);
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+		if (is_dev_loop(buffer)) {
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+			ret = true;
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+			break;
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+		}
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+	}
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+	closedir(dir);
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+free_buffer:
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+	free(buffer);
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+	return ret;
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+}
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+
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 static int vss_operate(int operation)
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 {
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 	char match[] = "/dev/";
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@@ -75,6 +126,7 @@ static int vss_operate(int operation)
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 	struct mntent *ent;
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 	struct stat sb;
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 	char errdir[1024] = {0};
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+	char blkdir[23]; /* /sys/dev/block/XXX:XXX */
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 	unsigned int cmd;
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 	int error = 0, root_seen = 0, save_errno = 0;
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@@ -96,10 +148,15 @@ static int vss_operate(int operation)
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 	while ((ent = getmntent(mounts))) {
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 		if (strncmp(ent->mnt_fsname, match, strlen(match)))
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 			continue;
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-		if (stat(ent->mnt_fsname, &sb) == -1)
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-			continue;
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-		if (S_ISBLK(sb.st_mode) && major(sb.st_rdev) == LOOP_MAJOR)
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-			continue;
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+		if (stat(ent->mnt_fsname, &sb)) {
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+			syslog(LOG_ERR, "Can't stat: %s; error:%d %s!",
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+			       ent->mnt_fsname, errno, strerror(errno));
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+		} else {
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+			sprintf(blkdir, "/sys/dev/block/%d:%d",
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+				major(sb.st_rdev), minor(sb.st_rdev));
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+			if (is_dev_loop(blkdir))
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+				continue;
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+		}
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 		if (hasmntopt(ent, MNTOPT_RO) != NULL)
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 			continue;
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 		if (strcmp(ent->mnt_type, "vfat") == 0)
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-- 
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2.14.4
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