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108a454a46
Modern bootloaders leverage data stored in the root filesystem to enable some of their powerful features. GRUB specifically has a grubenv file which can store large amounts of configuration data that can be read and written at boot time and during normal operation. This allows sysadmins to configure useful features like automated failover after failed boot attempts. Unfortunately, due to the Copy-on-Write nature of ZFS, the standard behavior of these tools cannot handle writing to ZFS files safely at boot time. We need an alternative way to store data that allows the bootloader to make changes to the data. This work is very similar to work that was done on Illumos to enable similar functionality in the FreeBSD bootloader. This patch is different in that the data being stored is a raw grubenv file; this file can store arbitrary variables and values, and the scripting provided by grub is powerful enough that special structures are not required to implement advanced behavior. We repurpose the second padding area in each label to store the grubenv file, protected by an embedded checksum. We add two ioctls to get and set this data, and libzfs_core and libzfs functions to access them more easily. There are no direct command line interfaces to these functions; these will be added directly to the bootloader utilities. Reviewed-by: Pavel Zakharov <pavel.zakharov@delphix.com> Reviewed-by: Matthew Ahrens <mahrens@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Signed-off-by: Paul Dagnelie <pcd@delphix.com> Closes #10009
75 lines
2.0 KiB
C
75 lines
2.0 KiB
C
/*
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* CDDL HEADER START
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*
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* The contents of this file are subject to the terms of the
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* Common Development and Distribution License (the "License").
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* You may not use this file except in compliance with the License.
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*
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* You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
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* or http://www.opensolaris.org/os/licensing.
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* See the License for the specific language governing permissions
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* and limitations under the License.
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*
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* When distributing Covered Code, include this CDDL HEADER in each
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* file and include the License file at usr/src/OPENSOLARIS.LICENSE.
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* If applicable, add the following below this CDDL HEADER, with the
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* fields enclosed by brackets "[]" replaced with your own identifying
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* information: Portions Copyright [yyyy] [name of copyright owner]
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*
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* CDDL HEADER END
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*/
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#include <sys/zfs_context.h>
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#include <sys/spa.h>
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#include <sys/spa_impl.h>
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#include <sys/dmu.h>
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#include <sys/zap.h>
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#include <sys/vdev.h>
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#include <sys/vdev_os.h>
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#include <sys/vdev_impl.h>
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#include <sys/uberblock_impl.h>
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#include <sys/metaslab.h>
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#include <sys/metaslab_impl.h>
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#include <sys/zio.h>
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#include <sys/dsl_scan.h>
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#include <sys/abd.h>
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#include <sys/fs/zfs.h>
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int
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vdev_label_write_pad2(vdev_t *vd, const char *buf, size_t size)
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{
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spa_t *spa = vd->vdev_spa;
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zio_t *zio;
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abd_t *pad2;
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int flags = ZIO_FLAG_CONFIG_WRITER | ZIO_FLAG_CANFAIL;
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int error;
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if (size > VDEV_PAD_SIZE)
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return (EINVAL);
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if (!vd->vdev_ops->vdev_op_leaf)
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return (ENODEV);
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if (vdev_is_dead(vd))
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return (ENXIO);
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ASSERT(spa_config_held(spa, SCL_ALL, RW_WRITER) == SCL_ALL);
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pad2 = abd_alloc_for_io(VDEV_PAD_SIZE, B_TRUE);
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abd_zero(pad2, VDEV_PAD_SIZE);
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abd_copy_from_buf(pad2, buf, size);
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retry:
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zio = zio_root(spa, NULL, NULL, flags);
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vdev_label_write(zio, vd, 0, pad2,
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offsetof(vdev_label_t, vl_be),
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VDEV_PAD_SIZE, NULL, NULL, flags);
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error = zio_wait(zio);
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if (error != 0 && !(flags & ZIO_FLAG_TRYHARD)) {
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flags |= ZIO_FLAG_TRYHARD;
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goto retry;
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}
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abd_free(pad2);
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return (error);
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}
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