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In r290196 the root mount hold mechanism was changed to make it not wait

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for mount hold release if the root device already exists.  So, unless your
rootdev is not on USB - ie in the usual case - the root mount won't wait
for USB.  However, the old behaviour was sometimes used as "wait until USB
is fully enumerated", and r290196 broke that.

This commit adds vfs.root_mount_always_wait tunable, to force the kernel
to always wait for root mount holds, even if the root is already there.

Reviewed by:	kib
MFC after:	2 weeks
Relnotes:	yes
Sponsored by:	DARPA, AFRL
Differential Revision:	https://reviews.freebsd.org/D9387
This commit is contained in:
Edward Tomasz Napierala 2017-02-06 20:36:59 +00:00
parent 7b02037ef8
commit 4f9d7bad48
1 changed files with 8 additions and 2 deletions
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10
sys/kern/vfs_mountroot.c
View File

@ -132,6 +132,11 @@ static int root_mount_complete;
static int root_mount_timeout = 3;
TUNABLE_INT("vfs.mountroot.timeout", &root_mount_timeout);
static int root_mount_always_wait = 0;
SYSCTL_INT(_vfs, OID_AUTO, root_mount_always_wait, CTLFLAG_RDTUN,
&root_mount_always_wait, 0,
"Wait for root mount holds even if the root device already exists");
SYSCTL_PROC(_vfs, OID_AUTO, root_mount_hold,
CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_MPSAFE,
NULL, 0, sysctl_vfs_root_mount_hold, "A",
@ -961,10 +966,11 @@ vfs_mountroot_wait_if_neccessary(const char *fs, const char *dev)
/*
* In case of ZFS and NFS we don't have a way to wait for
* specific device.
* specific device. Also do the wait if the user forced that
* behaviour by setting vfs.root_mount_always_wait=1.
*/
if (strcmp(fs, "zfs") == 0 || strstr(fs, "nfs") != NULL ||
dev[0] == '\0') {
dev[0] == '\0' || root_mount_always_wait != 0) {
vfs_mountroot_wait();
return (0);
}