From 039df36231335fabe4da1a22fa3accb160d8bc1b Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Wed, 12 Apr 2017 16:29:04 +1000 Subject: [RHEL7.5 PATCH 072/169] mdopen: use parameters/new_array to create arrays whenever possible. In a sufficiently recent kernel, an md%d array can be created by writing to .../parameters/new_array. If mdadm does this consistently, then another new feature, disabling create_on_open, can be enabled. This avoids races on shutdown. An added benefit of using new_array (where available) is that it allows md arrays with numbers larger than 511 (e.g. md999) to be created. The old create_on_open mechanism doesn't support such devices since Commit: af5628f05db6 ("md: disable probing for md devices 512 and over.") in Linux 3.17. After a few more mdadm releases it would be good to have mdadm disable create_on_open automatically. Signed-off-by: NeilBrown Signed-off-by: Jes Sorensen --- mdopen.c | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/mdopen.c b/mdopen.c index fe240e5..82b97fc 100644 --- a/mdopen.c +++ b/mdopen.c @@ -313,6 +313,18 @@ int create_mddev(char *dev, char *name, int autof, int trustworthy, if (n < 0) devnm[0] = 0; } + if (num >= 0) { + int fd; + int n = -1; + sprintf(devnm, "md%d", num); + 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) + devnm[0] = 0; + } if (devnm[0]) ; else if (num < 0) { -- 2.7.4