Remove Giant acquisition from the mount and unmount pathes.
It could be claimed that two things were reasonable protected by Giant. One is vfsconf list links, which is converted to the new dedicated sx vfsconf_sx. Another is vfsconf.vfc_refcount, which is now updated with atomics. Note that vfc_refcount still has the same races now as it has under the Giant, the unload of filesystem modules can happen while the module is still in use. Tested by: pho Sponsored by: The FreeBSD Foundation MFC after: 2 weeks
This commit is contained in:
Konstantin Belousov
parent
8aeed43915
commit
168f4ee0a8
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=269457
@ -44,6 +44,7 @@ __FBSDID("$FreeBSD$");
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#include <sys/linker.h>
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#include <sys/mount.h>
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#include <sys/proc.h>
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#include <sys/sx.h>
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#include <sys/syscallsubr.h>
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#include <sys/sysctl.h>
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#include <sys/vnode.h>
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@ -64,6 +65,8 @@ int maxvfsconf = VFS_GENERIC + 1;
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* New entries are added/deleted by vfs_register()/vfs_unregister()
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*/
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struct vfsconfhead vfsconf = TAILQ_HEAD_INITIALIZER(vfsconf);
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struct sx vfsconf_sx;
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SX_SYSINIT(vfsconf, &vfsconf_sx, "vfsconf");
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/*
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* Loader.conf variable vfs.typenumhash enables setting vfc_typenum using a hash
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@ -104,17 +107,30 @@ struct vattr va_null;
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* Routines having to do with the management of the vnode table.
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*/
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static struct vfsconf *
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vfs_byname_locked(const char *name)
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{
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struct vfsconf *vfsp;
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sx_assert(&vfsconf_sx, SA_LOCKED);
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if (!strcmp(name, "ffs"))
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name = "ufs";
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TAILQ_FOREACH(vfsp, &vfsconf, vfc_list) {
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if (!strcmp(name, vfsp->vfc_name))
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return (vfsp);
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}
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return (NULL);
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}
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struct vfsconf *
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vfs_byname(const char *name)
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{
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struct vfsconf *vfsp;
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if (!strcmp(name, "ffs"))
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name = "ufs";
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TAILQ_FOREACH(vfsp, &vfsconf, vfc_list)
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if (!strcmp(name, vfsp->vfc_name))
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return (vfsp);
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return (NULL);
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vfsconf_slock();
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vfsp = vfs_byname_locked(name);
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vfsconf_sunlock();
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return (vfsp);
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}
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struct vfsconf *
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@ -168,8 +184,11 @@ vfs_register(struct vfsconf *vfc)
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vfc->vfc_name, vfc->vfc_version);
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return (EINVAL);
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}
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if (vfs_byname(vfc->vfc_name) != NULL)
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vfsconf_lock();
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if (vfs_byname_locked(vfc->vfc_name) != NULL) {
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vfsconf_unlock();
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return (EEXIST);
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}
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if (vfs_typenumhash != 0) {
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/*
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@ -201,26 +220,6 @@ vfs_register(struct vfsconf *vfc)
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vfc->vfc_typenum = maxvfsconf++;
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TAILQ_INSERT_TAIL(&vfsconf, vfc, vfc_list);
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/*
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* If this filesystem has a sysctl node under vfs
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* (i.e. vfs.xxfs), then change the oid number of that node to
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* match the filesystem's type number. This allows user code
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* which uses the type number to read sysctl variables defined
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* by the filesystem to continue working. Since the oids are
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* in a sorted list, we need to make sure the order is
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* preserved by re-registering the oid after modifying its
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* number.
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*/
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sysctl_lock();
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SLIST_FOREACH(oidp, SYSCTL_CHILDREN(&sysctl___vfs), oid_link)
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if (strcmp(oidp->oid_name, vfc->vfc_name) == 0) {
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sysctl_unregister_oid(oidp);
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oidp->oid_number = vfc->vfc_typenum;
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sysctl_register_oid(oidp);
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break;
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}
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sysctl_unlock();
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/*
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* Initialise unused ``struct vfsops'' fields, to use
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* the vfs_std*() functions. Note, we need the mount
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@ -280,8 +279,30 @@ vfs_register(struct vfsconf *vfc)
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* Call init function for this VFS...
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*/
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(*(vfc->vfc_vfsops->vfs_init))(vfc);
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vfsconf_unlock();
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return 0;
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/*
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* If this filesystem has a sysctl node under vfs
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* (i.e. vfs.xxfs), then change the oid number of that node to
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* match the filesystem's type number. This allows user code
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* which uses the type number to read sysctl variables defined
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* by the filesystem to continue working. Since the oids are
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* in a sorted list, we need to make sure the order is
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* preserved by re-registering the oid after modifying its
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* number.
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*/
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sysctl_lock();
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SLIST_FOREACH(oidp, SYSCTL_CHILDREN(&sysctl___vfs), oid_link) {
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if (strcmp(oidp->oid_name, vfc->vfc_name) == 0) {
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sysctl_unregister_oid(oidp);
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oidp->oid_number = vfc->vfc_typenum;
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sysctl_register_oid(oidp);
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break;
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}
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}
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sysctl_unlock();
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return (0);
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}
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@ -294,15 +315,22 @@ vfs_unregister(struct vfsconf *vfc)
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i = vfc->vfc_typenum;
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vfsp = vfs_byname(vfc->vfc_name);
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if (vfsp == NULL)
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return EINVAL;
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if (vfsp->vfc_refcount)
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return EBUSY;
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vfsconf_lock();
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vfsp = vfs_byname_locked(vfc->vfc_name);
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if (vfsp == NULL) {
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vfsconf_unlock();
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return (EINVAL);
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}
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if (vfsp->vfc_refcount != 0) {
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vfsconf_unlock();
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return (EBUSY);
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}
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if (vfc->vfc_vfsops->vfs_uninit != NULL) {
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error = (*vfc->vfc_vfsops->vfs_uninit)(vfsp);
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if (error)
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if (error != 0) {
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vfsconf_unlock();
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return (error);
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}
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}
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TAILQ_REMOVE(&vfsconf, vfsp, vfc_list);
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maxtypenum = VFS_GENERIC;
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@ -310,7 +338,8 @@ vfs_unregister(struct vfsconf *vfc)
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if (maxtypenum < vfsp->vfc_typenum)
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maxtypenum = vfsp->vfc_typenum;
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maxvfsconf = maxtypenum + 1;
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return 0;
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vfsconf_unlock();
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return (0);
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}
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/*
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@ -463,9 +463,9 @@ vfs_mount_alloc(struct vnode *vp, struct vfsconf *vfsp, const char *fspath,
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mp->mnt_activevnodelistsize = 0;
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mp->mnt_ref = 0;
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(void) vfs_busy(mp, MBF_NOWAIT);
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atomic_add_acq_int(&vfsp->vfc_refcount, 1);
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mp->mnt_op = vfsp->vfc_vfsops;
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mp->mnt_vfc = vfsp;
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vfsp->vfc_refcount++; /* XXX Unlocked */
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mp->mnt_stat.f_type = vfsp->vfc_typenum;
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mp->mnt_gen++;
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strlcpy(mp->mnt_stat.f_fstypename, vfsp->vfc_name, MFSNAMELEN);
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@ -505,7 +505,7 @@ vfs_mount_destroy(struct mount *mp)
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panic("vfs_mount_destroy: nonzero writeopcount");
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if (mp->mnt_secondary_writes != 0)
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panic("vfs_mount_destroy: nonzero secondary_writes");
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mp->mnt_vfc->vfc_refcount--;
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atomic_subtract_rel_int(&mp->mnt_vfc->vfc_refcount, 1);
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if (!TAILQ_EMPTY(&mp->mnt_nvnodelist)) {
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struct vnode *vp;
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@ -736,17 +736,12 @@ sys_mount(td, uap)
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}
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AUDIT_ARG_TEXT(fstype);
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mtx_lock(&Giant);
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vfsp = vfs_byname_kld(fstype, td, &error);
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free(fstype, M_TEMP);
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if (vfsp == NULL) {
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mtx_unlock(&Giant);
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if (vfsp == NULL)
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return (ENOENT);
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}
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if (vfsp->vfc_vfsops->vfs_cmount == NULL) {
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mtx_unlock(&Giant);
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if (vfsp->vfc_vfsops->vfs_cmount == NULL)
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return (EOPNOTSUPP);
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}
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ma = mount_argsu(ma, "fstype", uap->type, MFSNAMELEN);
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ma = mount_argsu(ma, "fspath", uap->path, MNAMELEN);
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@ -755,7 +750,6 @@ sys_mount(td, uap)
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ma = mount_argb(ma, !(flags & MNT_NOEXEC), "noexec");
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error = vfsp->vfc_vfsops->vfs_cmount(ma, uap->data, flags);
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mtx_unlock(&Giant);
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return (error);
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}
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@ -777,7 +771,6 @@ vfs_domount_first(
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struct vnode *newdp;
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int error;
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mtx_assert(&Giant, MA_OWNED);
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ASSERT_VOP_ELOCKED(vp, __func__);
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KASSERT((fsflags & MNT_UPDATE) == 0, ("MNT_UPDATE shouldn't be here"));
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@ -889,7 +882,6 @@ vfs_domount_update(
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int error, export_error;
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uint64_t flag;
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mtx_assert(&Giant, MA_OWNED);
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ASSERT_VOP_ELOCKED(vp, __func__);
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KASSERT((fsflags & MNT_UPDATE) != 0, ("MNT_UPDATE should be here"));
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@ -1091,7 +1083,6 @@ vfs_domount(
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error = namei(&nd);
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if (error != 0)
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return (error);
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mtx_lock(&Giant);
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NDFREE(&nd, NDF_ONLY_PNBUF);
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vp = nd.ni_vp;
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if ((fsflags & MNT_UPDATE) == 0) {
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@ -1106,7 +1097,6 @@ vfs_domount(
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free(pathbuf, M_TEMP);
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} else
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error = vfs_domount_update(td, vp, fsflags, optlist);
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mtx_unlock(&Giant);
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ASSERT_VI_UNLOCKED(vp, __func__);
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ASSERT_VOP_UNLOCKED(vp, __func__);
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@ -1153,12 +1143,10 @@ sys_unmount(td, uap)
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free(pathbuf, M_TEMP);
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return (error);
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}
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mtx_lock(&Giant);
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if (uap->flags & MNT_BYFSID) {
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AUDIT_ARG_TEXT(pathbuf);
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/* Decode the filesystem ID. */
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if (sscanf(pathbuf, "FSID:%d:%d", &id0, &id1) != 2) {
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mtx_unlock(&Giant);
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free(pathbuf, M_TEMP);
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return (EINVAL);
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}
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@ -1198,19 +1186,15 @@ sys_unmount(td, uap)
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* now, so in the !MNT_BYFSID case return the more likely
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* EINVAL for compatibility.
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*/
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mtx_unlock(&Giant);
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return ((uap->flags & MNT_BYFSID) ? ENOENT : EINVAL);
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}
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/*
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* Don't allow unmounting the root filesystem.
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*/
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if (mp->mnt_flag & MNT_ROOTFS) {
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mtx_unlock(&Giant);
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if (mp->mnt_flag & MNT_ROOTFS)
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return (EINVAL);
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}
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error = dounmount(mp, uap->flags, td);
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mtx_unlock(&Giant);
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return (error);
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}
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@ -1228,8 +1212,6 @@ dounmount(mp, flags, td)
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uint64_t async_flag;
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int mnt_gen_r;
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mtx_assert(&Giant, MA_OWNED);
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if ((coveredvp = mp->mnt_vnodecovered) != NULL) {
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mnt_gen_r = mp->mnt_gen;
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VI_LOCK(coveredvp);
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@ -3233,6 +3233,7 @@ sysctl_vfs_conflist(SYSCTL_HANDLER_ARGS)
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int error;
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error = 0;
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vfsconf_slock();
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TAILQ_FOREACH(vfsp, &vfsconf, vfc_list) {
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#ifdef COMPAT_FREEBSD32
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if (req->flags & SCTL_MASK32)
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@ -3243,11 +3244,12 @@ sysctl_vfs_conflist(SYSCTL_HANDLER_ARGS)
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if (error)
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break;
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}
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vfsconf_sunlock();
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return (error);
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}
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SYSCTL_PROC(_vfs, OID_AUTO, conflist, CTLTYPE_OPAQUE | CTLFLAG_RD,
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NULL, 0, sysctl_vfs_conflist,
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SYSCTL_PROC(_vfs, OID_AUTO, conflist, CTLTYPE_OPAQUE | CTLFLAG_RD |
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CTLFLAG_MPSAFE, NULL, 0, sysctl_vfs_conflist,
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"S,xvfsconf", "List of all configured filesystems");
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#ifndef BURN_BRIDGES
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@ -3277,9 +3279,12 @@ vfs_sysctl(SYSCTL_HANDLER_ARGS)
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case VFS_CONF:
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if (namelen != 3)
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return (ENOTDIR); /* overloaded */
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TAILQ_FOREACH(vfsp, &vfsconf, vfc_list)
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vfsconf_slock();
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TAILQ_FOREACH(vfsp, &vfsconf, vfc_list) {
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if (vfsp->vfc_typenum == name[2])
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break;
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}
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vfsconf_sunlock();
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if (vfsp == NULL)
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return (EOPNOTSUPP);
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#ifdef COMPAT_FREEBSD32
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@ -3292,8 +3297,9 @@ vfs_sysctl(SYSCTL_HANDLER_ARGS)
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return (EOPNOTSUPP);
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}
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static SYSCTL_NODE(_vfs, VFS_GENERIC, generic, CTLFLAG_RD | CTLFLAG_SKIP,
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vfs_sysctl, "Generic filesystem");
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static SYSCTL_NODE(_vfs, VFS_GENERIC, generic, CTLFLAG_RD | CTLFLAG_SKIP |
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CTLFLAG_MPSAFE, vfs_sysctl,
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"Generic filesystem");
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#if 1 || defined(COMPAT_PRELITE2)
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@ -3304,6 +3310,7 @@ sysctl_ovfs_conf(SYSCTL_HANDLER_ARGS)
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struct vfsconf *vfsp;
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struct ovfsconf ovfs;
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vfsconf_slock();
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TAILQ_FOREACH(vfsp, &vfsconf, vfc_list) {
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bzero(&ovfs, sizeof(ovfs));
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ovfs.vfc_vfsops = vfsp->vfc_vfsops; /* XXX used as flag */
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@ -3312,10 +3319,13 @@ sysctl_ovfs_conf(SYSCTL_HANDLER_ARGS)
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ovfs.vfc_refcount = vfsp->vfc_refcount;
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ovfs.vfc_flags = vfsp->vfc_flags;
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error = SYSCTL_OUT(req, &ovfs, sizeof ovfs);
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if (error)
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return error;
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if (error != 0) {
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vfsconf_sunlock();
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return (error);
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}
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}
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return 0;
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vfsconf_sunlock();
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return (0);
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}
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#endif /* 1 || COMPAT_PRELITE2 */
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@ -3413,8 +3423,9 @@ sysctl_vnode(SYSCTL_HANDLER_ARGS)
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return (error);
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}
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SYSCTL_PROC(_kern, KERN_VNODE, vnode, CTLTYPE_OPAQUE|CTLFLAG_RD,
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0, 0, sysctl_vnode, "S,xvnode", "");
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SYSCTL_PROC(_kern, KERN_VNODE, vnode, CTLTYPE_OPAQUE | CTLFLAG_RD |
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CTLFLAG_MPSAFE, 0, 0, sysctl_vnode, "S,xvnode",
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"");
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#endif
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/*
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@ -39,6 +39,7 @@
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#include <sys/lock.h>
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#include <sys/lockmgr.h>
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#include <sys/_mutex.h>
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#include <sys/_sx.h>
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#endif
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/*
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@ -889,6 +890,11 @@ void vfs_unmountall(void);
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extern TAILQ_HEAD(mntlist, mount) mountlist; /* mounted filesystem list */
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extern struct mtx mountlist_mtx;
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extern struct nfs_public nfs_pub;
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extern struct sx vfsconf_sx;
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#define vfsconf_lock() sx_xlock(&vfsconf_sx)
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#define vfsconf_unlock() sx_xunlock(&vfsconf_sx)
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#define vfsconf_slock() sx_slock(&vfsconf_sx)
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#define vfsconf_sunlock() sx_sunlock(&vfsconf_sx)
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/*
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* Declarations for these vfs default operations are located in
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