git: a849842f510a - main - loader: Add support for booting from a ZFS snapshot
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Date: Tue, 14 Mar 2023 14:19:37 UTC
The branch main has been updated by allanjude: URL: https://cgit.FreeBSD.org/src/commit/?id=a849842f510af48717e35ff709623e0dd1b80b20 commit a849842f510af48717e35ff709623e0dd1b80b20 Author: Allan Jude <allanjude@FreeBSD.org> AuthorDate: 2022-11-26 18:11:13 +0000 Commit: Allan Jude <allanjude@FreeBSD.org> CommitDate: 2023-03-14 14:18:29 +0000 loader: Add support for booting from a ZFS snapshot When booting from a snapshot we need to follow a different code path to turn the objset ID into the name, and for forward lookups we need to walk the parent's snapnames_zap. With this, it is possible to set the pools BOOTFS property to a snapshot and boot with a read-only filesystem of that snapshot. Reviewed by: tsoome, rew, imp Sponsored By: Beckhoff Automation GmbH & Co. KG Sponsored By: Klara, Inc. Differential Revision: https://reviews.freebsd.org/D38600 --- stand/libsa/zfs/zfsimpl.c | 56 +++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 54 insertions(+), 2 deletions(-) diff --git a/stand/libsa/zfs/zfsimpl.c b/stand/libsa/zfs/zfsimpl.c index 36c90613e827..76063e76225f 100644 --- a/stand/libsa/zfs/zfsimpl.c +++ b/stand/libsa/zfs/zfsimpl.c @@ -3068,11 +3068,12 @@ zfs_rlookup(const spa_t *spa, uint64_t objnum, char *result) char name[256]; char component[256]; uint64_t dir_obj, parent_obj, child_dir_zapobj; - dnode_phys_t child_dir_zap, dataset, dir, parent; + dnode_phys_t child_dir_zap, snapnames_zap, dataset, dir, parent; dsl_dir_phys_t *dd; dsl_dataset_phys_t *ds; char *p; int len; + boolean_t issnap = B_FALSE; p = &name[sizeof(name) - 1]; *p = '\0'; @@ -3083,6 +3084,8 @@ zfs_rlookup(const spa_t *spa, uint64_t objnum, char *result) } ds = (dsl_dataset_phys_t *)&dataset.dn_bonus; dir_obj = ds->ds_dir_obj; + if (ds->ds_snapnames_zapobj == 0) + issnap = B_TRUE; for (;;) { if (objset_get_dnode(spa, spa->spa_mos, dir_obj, &dir) != 0) @@ -3098,6 +3101,34 @@ zfs_rlookup(const spa_t *spa, uint64_t objnum, char *result) &parent) != 0) return (EIO); dd = (dsl_dir_phys_t *)&parent.dn_bonus; + if (issnap == B_TRUE) { + /* + * The dataset we are looking up is a snapshot + * the dir_obj is the parent already, we don't want + * the grandparent just yet. Reset to the parent. + */ + dd = (dsl_dir_phys_t *)&dir.dn_bonus; + /* Lookup the dataset to get the snapname ZAP */ + if (objset_get_dnode(spa, spa->spa_mos, + dd->dd_head_dataset_obj, &dataset)) + return (EIO); + ds = (dsl_dataset_phys_t *)&dataset.dn_bonus; + if (objset_get_dnode(spa, spa->spa_mos, + ds->ds_snapnames_zapobj, &snapnames_zap) != 0) + return (EIO); + /* Get the name of the snapshot */ + if (zap_rlookup(spa, &snapnames_zap, component, + objnum) != 0) + return (EIO); + len = strlen(component); + p -= len; + memcpy(p, component, len); + --p; + *p = '@'; + issnap = B_FALSE; + continue; + } + child_dir_zapobj = dd->dd_child_dir_zapobj; if (objset_get_dnode(spa, spa->spa_mos, child_dir_zapobj, &child_dir_zap) != 0) @@ -3127,9 +3158,11 @@ zfs_lookup_dataset(const spa_t *spa, const char *name, uint64_t *objnum) { char element[256]; uint64_t dir_obj, child_dir_zapobj; - dnode_phys_t child_dir_zap, dir; + dnode_phys_t child_dir_zap, snapnames_zap, dir, dataset; dsl_dir_phys_t *dd; + dsl_dataset_phys_t *ds; const char *p, *q; + boolean_t issnap = B_FALSE; if (objset_get_dnode(spa, spa->spa_mos, DMU_POOL_DIRECTORY_OBJECT, &dir)) @@ -3160,6 +3193,25 @@ zfs_lookup_dataset(const spa_t *spa, const char *name, uint64_t *objnum) p += strlen(p); } + if (issnap == B_TRUE) { + if (objset_get_dnode(spa, spa->spa_mos, + dd->dd_head_dataset_obj, &dataset)) + return (EIO); + ds = (dsl_dataset_phys_t *)&dataset.dn_bonus; + if (objset_get_dnode(spa, spa->spa_mos, + ds->ds_snapnames_zapobj, &snapnames_zap) != 0) + return (EIO); + /* Actual loop condition #2. */ + if (zap_lookup(spa, &snapnames_zap, element, + sizeof (dir_obj), 1, &dir_obj) != 0) + return (ENOENT); + *objnum = dir_obj; + return (0); + } else if ((q = strchr(element, '@')) != NULL) { + issnap = B_TRUE; + element[q - element] = '\0'; + p = q + 1; + } child_dir_zapobj = dd->dd_child_dir_zapobj; if (objset_get_dnode(spa, spa->spa_mos, child_dir_zapobj, &child_dir_zap) != 0)