[dm-devel] [mdadm PATCH] Create: tell udev md device is not ready when first created.
Peter Rajnoha
prajnoha at redhat.com
Fri Apr 28 09:28:08 UTC 2017
On 04/28/2017 07:05 AM, NeilBrown wrote:
>
> When an array is created the content is not initialized,
> so it could have remnants of an old filesystem or md array
> etc on it.
> udev will see this and might try to activate it, which is almost
> certainly not what is wanted.
>
> So create a mechanism for mdadm to communicate with udev to tell
> it that the device isn't ready. This mechanism is the existance
> of a file /run/mdadm/created-mdXXX where mdXXX is the md device name.
>
> When creating an array, mdadm will create the file.
> A new udev rule file, 01-md-raid-creating.rules, will detect the
> precense of thst file and set ENV{SYSTEMD_READY}="0".
> This is fairly uniformly used to suppress actions based on the
> contents of the device.
>
The scans in udev are primarily directed by blkid call which detects the
signatures and based on this information various other udev rules fire.
The blkid as well as wipefs uses common libblkid library to detect these
signatures - is mdadm going to use libblkid to wipe the signatures on MD
device initialization or is it relying on external tools to do this? How
is mdadm actually initializing/wiping the newly created MD device?
--
Peter
> Signed-off-by: NeilBrown <neilb at suse.com>
> ---
> Assemble.c | 2 +-
> Build.c | 2 +-
> Create.c | 9 +++++++-
> Incremental.c | 4 ++--
> Makefile | 4 ++--
> lib.c | 29 +++++++++++++++++++++++++
> mdadm.h | 4 +++-
> mdopen.c | 52 ++++++++++++++++++++++++++++-----------------
> udev-md-raid-creating.rules | 7 ++++++
> 9 files changed, 86 insertions(+), 27 deletions(-)
> create mode 100644 udev-md-raid-creating.rules
>
> diff --git a/Assemble.c b/Assemble.c
> index d6beb23da9c5..a9442c8ce73b 100644
> --- a/Assemble.c
> +++ b/Assemble.c
> @@ -1478,7 +1478,7 @@ try_again:
> name = strchr(name, ':')+1;
>
> mdfd = create_mddev(mddev, name, ident->autof, trustworthy,
> - chosen_name);
> + chosen_name, 0);
> }
> if (mdfd < 0) {
> st->ss->free_super(st);
> diff --git a/Build.c b/Build.c
> index 11ba12f4ae7d..665d9067b8d6 100644
> --- a/Build.c
> +++ b/Build.c
> @@ -109,7 +109,7 @@ int Build(char *mddev, struct mddev_dev *devlist,
> /* We need to create the device. It can have no name. */
> map_lock(&map);
> mdfd = create_mddev(mddev, NULL, c->autof, LOCAL,
> - chosen_name);
> + chosen_name, 0);
> if (mdfd < 0) {
> map_unlock(&map);
> return 1;
> diff --git a/Create.c b/Create.c
> index 6ca092449880..df1bc20c635b 100644
> --- a/Create.c
> +++ b/Create.c
> @@ -605,7 +605,7 @@ int Create(struct supertype *st, char *mddev,
>
> /* We need to create the device */
> map_lock(&map);
> - mdfd = create_mddev(mddev, name, c->autof, LOCAL, chosen_name);
> + mdfd = create_mddev(mddev, name, c->autof, LOCAL, chosen_name, 1);
> if (mdfd < 0) {
> map_unlock(&map);
> return 1;
> @@ -620,6 +620,7 @@ int Create(struct supertype *st, char *mddev,
> chosen_name);
> close(mdfd);
> map_unlock(&map);
> + udev_unblock();
> return 1;
> }
> mddev = chosen_name;
> @@ -1053,9 +1054,15 @@ int Create(struct supertype *st, char *mddev,
> pr_err("not starting array - not enough devices.\n");
> }
> close(mdfd);
> + /* Give udev a moment to process the Change event caused
> + * by the close.
> + */
> + usleep(100*1000);
> + udev_unblock();
> return 0;
>
> abort:
> + udev_unblock();
> map_lock(&map);
> abort_locked:
> map_remove(&map, fd2devnm(mdfd));
> diff --git a/Incremental.c b/Incremental.c
> index 28f1f7734956..63ed4fa1a88d 100644
> --- a/Incremental.c
> +++ b/Incremental.c
> @@ -321,7 +321,7 @@ int Incremental(struct mddev_dev *devlist, struct context *c,
>
> /* Couldn't find an existing array, maybe make a new one */
> mdfd = create_mddev(match ? match->devname : NULL,
> - name_to_use, c->autof, trustworthy, chosen_name);
> + name_to_use, c->autof, trustworthy, chosen_name, 0);
>
> if (mdfd < 0)
> goto out_unlock;
> @@ -1605,7 +1605,7 @@ static int Incremental_container(struct supertype *st, char *devname,
> ra->name,
> c->autof,
> trustworthy,
> - chosen_name);
> + chosen_name, 0);
> }
> if (only && (!mp || strcmp(mp->devnm, only) != 0))
> continue;
> diff --git a/Makefile b/Makefile
> index 685069612617..021d3adf3ed1 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -256,8 +256,8 @@ install-man: mdadm.8 md.4 mdadm.conf.5 mdmon.8
> $(INSTALL) -D -m 644 md.4 $(DESTDIR)$(MAN4DIR)/md.4
> $(INSTALL) -D -m 644 mdadm.conf.5 $(DESTDIR)$(MAN5DIR)/mdadm.conf.5
>
> -install-udev: udev-md-raid-arrays.rules udev-md-raid-assembly.rules
> - @for file in 63-md-raid-arrays.rules 64-md-raid-assembly.rules ; \
> +install-udev: udev-md-raid-arrays.rules udev-md-raid-assembly.rules udev-md-raid-creating.rules
> + @for file in 01-md-raid-creating.rules 63-md-raid-arrays.rules 64-md-raid-assembly.rules ; \
> do sed -e 's,BINDIR,$(BINDIR),g' udev-$${file#??-} > .install.tmp.1 && \
> $(ECHO) $(INSTALL) -D -m 644 udev-$${file#??-} $(DESTDIR)$(UDEVDIR)/rules.d/$$file ; \
> $(INSTALL) -D -m 644 .install.tmp.1 $(DESTDIR)$(UDEVDIR)/rules.d/$$file ; \
> diff --git a/lib.c b/lib.c
> index b640634ef6f2..7e44b1f27fcc 100644
> --- a/lib.c
> +++ b/lib.c
> @@ -163,6 +163,35 @@ char *fd2devnm(int fd)
> return NULL;
> }
>
> +/* When we create a new array, we don't want the content to
> + * be immediately examined by udev - it is probably meaningless.
> + * So create /run/mdadm/creating-FOO and expect that a udev
> + * rule will noticed this and act accordingly.
> + */
> +static char block_path[] = "/run/mdadm/creating-%s";
> +static char *unblock_path = NULL;
> +void udev_block(char *devnm)
> +{
> + int fd;
> + char *path = NULL;
> +
> + xasprintf(&path, block_path, devnm);
> + fd = open(path, O_CREAT|O_RDWR, 0600);
> + if (fd >= 0) {
> + close(fd);
> + unblock_path = path;
> + } else
> + free(path);
> +}
> +
> +void udev_unblock(void)
> +{
> + if (unblock_path)
> + unlink(unblock_path);
> + free(unblock_path);
> + unblock_path = NULL;
> +}
> +
> /*
> * convert a major/minor pair for a block device into a name in /dev, if possible.
> * On the first call, walk /dev collecting name.
> diff --git a/mdadm.h b/mdadm.h
> index 1bbacfe9e916..6a382a7c1b90 100644
> --- a/mdadm.h
> +++ b/mdadm.h
> @@ -1533,7 +1533,7 @@ extern char *get_md_name(char *devnm);
> extern char DefaultConfFile[];
>
> extern int create_mddev(char *dev, char *name, int autof, int trustworthy,
> - char *chosen);
> + char *chosen, int block_udev);
> /* values for 'trustworthy' */
> #define LOCAL 1
> #define LOCAL_ANY 10
> @@ -1567,6 +1567,8 @@ extern char *stat2kname(struct stat *st);
> extern char *fd2kname(int fd);
> extern char *stat2devnm(struct stat *st);
> extern char *fd2devnm(int fd);
> +extern void udev_block(char *devnm);
> +extern void udev_unblock(void);
>
> extern int in_initrd(void);
>
> diff --git a/mdopen.c b/mdopen.c
> index 82b97fc90339..099efa0aa2e5 100644
> --- a/mdopen.c
> +++ b/mdopen.c
> @@ -135,7 +135,7 @@ void make_parts(char *dev, int cnt)
> */
>
> int create_mddev(char *dev, char *name, int autof, int trustworthy,
> - char *chosen)
> + char *chosen, int block_udev)
> {
> int mdfd;
> struct stat stb;
> @@ -147,6 +147,10 @@ int create_mddev(char *dev, char *name, int autof, int trustworthy,
> char devname[37];
> char devnm[32];
> char cbuf[400];
> +
> + if (!use_udev())
> + block_udev = 0;
> +
> if (chosen == NULL)
> chosen = cbuf;
>
> @@ -305,43 +309,53 @@ int create_mddev(char *dev, char *name, int autof, int trustworthy,
> int fd;
> int n = -1;
> sprintf(devnm, "md_%s", cname);
> + if (block_udev)
> + udev_block(devnm);
> fd = open("/sys/module/md_mod/parameters/new_array", O_WRONLY);
> if (fd >= 0) {
> n = write(fd, devnm, strlen(devnm));
> close(fd);
> }
> - if (n < 0)
> + if (n < 0) {
> devnm[0] = 0;
> + udev_unblock();
> + }
> }
> if (num >= 0) {
> int fd;
> int n = -1;
> sprintf(devnm, "md%d", num);
> + if (block_udev)
> + udev_block(devnm);
> fd = open("/sys/module/md_mod/parameters/new_array", O_WRONLY);
> if (fd >= 0) {
> n = write(fd, devnm, strlen(devnm));
> close(fd);
> }
> - if (n < 0)
> + if (n < 0) {
> devnm[0] = 0;
> - }
> - if (devnm[0])
> - ;
> - else if (num < 0) {
> - /* need to choose a free number. */
> - char *_devnm = find_free_devnm(use_mdp);
> - if (_devnm == NULL) {
> - pr_err("No avail md devices - aborting\n");
> - return -1;
> + udev_unblock();
> }
> - strcpy(devnm, _devnm);
> - } else {
> - sprintf(devnm, "%s%d", use_mdp?"md_d":"md", num);
> - if (mddev_busy(devnm)) {
> - pr_err("%s is already in use.\n",
> - dev);
> - return -1;
> + }
> + if (devnm[0] == 0) {
> + if (num < 0) {
> + /* need to choose a free number. */
> + char *_devnm = find_free_devnm(use_mdp);
> + if (_devnm == NULL) {
> + pr_err("No avail md devices - aborting\n");
> + return -1;
> + }
> + strcpy(devnm, _devnm);
> + } else {
> + sprintf(devnm, "%s%d", use_mdp?"md_d":"md", num);
> + if (mddev_busy(devnm)) {
> + pr_err("%s is already in use.\n",
> + dev);
> + return -1;
> + }
> }
> + if (block_udev)
> + udev_block(devnm);
> }
>
> sprintf(devname, "/dev/%s", devnm);
> diff --git a/udev-md-raid-creating.rules b/udev-md-raid-creating.rules
> new file mode 100644
> index 000000000000..2be466bcefd2
> --- /dev/null
> +++ b/udev-md-raid-creating.rules
> @@ -0,0 +1,7 @@
> +# do not edit this file, it will be overwritten on update
> +# While mdadm is creating an array, it creates a file
> +# /run/mdadm/creating-mdXXX. If that file exists, then
> +# the array is not "ready" and we should make sure the
> +# content is ignored.
> +
> +KERNEL=="md*", TEST="/run/mdadm/creating-$kernel", ENV{SYSTEMD_READY}="0"
>
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