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