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freebsd-skq/sys/kern/vnode_if.src
Konstantin Belousov 78022527bb Switch to use shared vnode locks for text files during image activation. 
kern_execve() locks text vnode exclusive to be able to set and clear
VV_TEXT flag. VV_TEXT is mutually exclusive with the v_writecount > 0
condition.

The change removes VV_TEXT, replacing it with the condition
v_writecount <= -1, and puts v_writecount under the vnode interlock.
Each text reference decrements v_writecount.  To clear the text
reference when the segment is unmapped, it is recorded in the
vm_map_entry backed by the text file as MAP_ENTRY_VN_TEXT flag, and
v_writecount is incremented on the map entry removal

The operations like VOP_ADD_WRITECOUNT() and VOP_SET_TEXT() check that
v_writecount does not contradict the desired change.  vn_writecheck()
is now racy and its use was eliminated everywhere except access.
Atomic check for writeability and increment of v_writecount is
performed by the VOP.  vn_truncate() now increments v_writecount
around VOP_SETATTR() call, lack of which is arguably a bug on its own.

nullfs bypasses v_writecount to the lower vnode always, so nullfs
vnode has its own v_writecount correct, and lower vnode gets all
references, since object->handle is always lower vnode.

On the text vnode' vm object dealloc, the v_writecount value is reset
to zero, and deadfs vop_unset_text short-circuit the operation.
Reclamation of lowervp always reclaims all nullfs vnodes referencing
lowervp first, so no stray references are left.

Reviewed by:	markj, trasz
Tested by:	mjg, pho
Sponsored by:	The FreeBSD Foundation
MFC after:	1 month
Differential revision:	https://reviews.freebsd.org/D19923
2019-05-05 11:20:43 +00:00

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#-
# Copyright (c) 1992, 1993
# The Regents of the University of California. All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions
# are met:
# 1. Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
# notice, this list of conditions and the following disclaimer in the
# documentation and/or other materials provided with the distribution.
# 3. Neither the name of the University nor the names of its contributors
# may be used to endorse or promote products derived from this software
# without specific prior written permission.
#
# THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
# ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
# SUCH DAMAGE.
#
# @(#)vnode_if.src 8.12 (Berkeley) 5/14/95
# $FreeBSD$
#
#
# Above each of the vop descriptors in lines starting with %%
# is a specification of the locking protocol used by each vop call.
# The first column is the name of the variable, the remaining three
# columns are in, out and error respectively. The "in" column defines
# the lock state on input, the "out" column defines the state on successful
# return, and the "error" column defines the locking state on error exit.
#
# The locking value can take the following values:
# L: locked; not converted to type of lock.
# E: locked with exclusive lock for this process.
# U: unlocked.
# -: not applicable. vnode does not yet (or no longer) exists.
# =: the same on input and output, may be either L or U.
#
# The paramater named "vpp" is assumed to be always used with double
# indirection (**vpp) and that name is hard-coded in vnode_if.awk !
#
# Lines starting with %! specify a pre or post-condition function
# to call before/after the vop call.
#
# If other such parameters are introduced, they have to be added to
# the AWK script at the head of the definition of "add_debug_code()".
#
vop_islocked {
IN struct vnode *vp;
};
%% lookup dvp L L L
%% lookup vpp - L -
# XXX - the lookup locking protocol defies simple description and depends
# on the flags and operation fields in the (cnp) structure. Note
# especially that *vpp may equal dvp and both may be locked.
vop_lookup {
IN struct vnode *dvp;
INOUT struct vnode **vpp;
IN struct componentname *cnp;
};
%% cachedlookup dvp L L L
%% cachedlookup vpp - L -
# This must be an exact copy of lookup. See kern/vfs_cache.c for details.
vop_cachedlookup {
IN struct vnode *dvp;
INOUT struct vnode **vpp;
IN struct componentname *cnp;
};
%% create dvp E E E
%% create vpp - L -
%! create post vop_create_post
vop_create {
IN struct vnode *dvp;
OUT struct vnode **vpp;
IN struct componentname *cnp;
IN struct vattr *vap;
};
%% whiteout dvp E E E
vop_whiteout {
IN struct vnode *dvp;
IN struct componentname *cnp;
IN int flags;
};
%% mknod dvp E E E
%% mknod vpp - L -
%! mknod post vop_mknod_post
vop_mknod {
IN struct vnode *dvp;
OUT struct vnode **vpp;
IN struct componentname *cnp;
IN struct vattr *vap;
};
%% open vp L L L
%! open post vop_open_post
vop_open {
IN struct vnode *vp;
IN int mode;
IN struct ucred *cred;
IN struct thread *td;
IN struct file *fp;
};
%% close vp L L L
%! close post vop_close_post
vop_close {
IN struct vnode *vp;
IN int fflag;
IN struct ucred *cred;
IN struct thread *td;
};
%% access vp L L L
vop_access {
IN struct vnode *vp;
IN accmode_t accmode;
IN struct ucred *cred;
IN struct thread *td;
};
%% accessx vp L L L
vop_accessx {
IN struct vnode *vp;
IN accmode_t accmode;
IN struct ucred *cred;
IN struct thread *td;
};
%% getattr vp L L L
vop_getattr {
IN struct vnode *vp;
OUT struct vattr *vap;
IN struct ucred *cred;
};
%% setattr vp E E E
%! setattr post vop_setattr_post
vop_setattr {
IN struct vnode *vp;
IN struct vattr *vap;
IN struct ucred *cred;
};
%% markatime vp L L L
vop_markatime {
IN struct vnode *vp;
};
%% read vp L L L
%! read post vop_read_post
vop_read {
IN struct vnode *vp;
INOUT struct uio *uio;
IN int ioflag;
IN struct ucred *cred;
};
%% write vp L L L
%! write pre VOP_WRITE_PRE
%! write post VOP_WRITE_POST
vop_write {
IN struct vnode *vp;
INOUT struct uio *uio;
IN int ioflag;
IN struct ucred *cred;
};
%% ioctl vp U U U
vop_ioctl {
IN struct vnode *vp;
IN u_long command;
IN void *data;
IN int fflag;
IN struct ucred *cred;
IN struct thread *td;
};
%% poll vp U U U
vop_poll {
IN struct vnode *vp;
IN int events;
IN struct ucred *cred;
IN struct thread *td;
};
%% kqfilter vp U U U
vop_kqfilter {
IN struct vnode *vp;
IN struct knote *kn;
};
%% revoke vp L L L
vop_revoke {
IN struct vnode *vp;
IN int flags;
};
%% fsync vp L L L
vop_fsync {
IN struct vnode *vp;
IN int waitfor;
IN struct thread *td;
};
%% remove dvp E E E
%% remove vp E E E
%! remove post vop_remove_post
vop_remove {
IN struct vnode *dvp;
IN struct vnode *vp;
IN struct componentname *cnp;
};
%% link tdvp E E E
%% link vp E E E
%! link post vop_link_post
vop_link {
IN struct vnode *tdvp;
IN struct vnode *vp;
IN struct componentname *cnp;
};
%! rename pre vop_rename_pre
%! rename post vop_rename_post
vop_rename {
IN WILLRELE struct vnode *fdvp;
IN WILLRELE struct vnode *fvp;
IN struct componentname *fcnp;
IN WILLRELE struct vnode *tdvp;
IN WILLRELE struct vnode *tvp;
IN struct componentname *tcnp;
};
%% mkdir dvp E E E
%% mkdir vpp - E -
%! mkdir post vop_mkdir_post
vop_mkdir {
IN struct vnode *dvp;
OUT struct vnode **vpp;
IN struct componentname *cnp;
IN struct vattr *vap;
};
%% rmdir dvp E E E
%% rmdir vp E E E
%! rmdir post vop_rmdir_post
vop_rmdir {
IN struct vnode *dvp;
IN struct vnode *vp;
IN struct componentname *cnp;
};
%% symlink dvp E E E
%% symlink vpp - E -
%! symlink post vop_symlink_post
vop_symlink {
IN struct vnode *dvp;
OUT struct vnode **vpp;
IN struct componentname *cnp;
IN struct vattr *vap;
IN const char *target;
};
%% readdir vp L L L
%! readdir post vop_readdir_post
vop_readdir {
IN struct vnode *vp;
INOUT struct uio *uio;
IN struct ucred *cred;
INOUT int *eofflag;
OUT int *ncookies;
INOUT u_long **cookies;
};
%% readlink vp L L L
vop_readlink {
IN struct vnode *vp;
INOUT struct uio *uio;
IN struct ucred *cred;
};
%% inactive vp E E E
vop_inactive {
IN struct vnode *vp;
IN struct thread *td;
};
%% reclaim vp E E E
%! reclaim post vop_reclaim_post
vop_reclaim {
IN struct vnode *vp;
IN struct thread *td;
};
%! lock1 pre vop_lock_pre
%! lock1 post vop_lock_post
vop_lock1 {
IN struct vnode *vp;
IN int flags;
IN char *file;
IN int line;
};
%! unlock pre vop_unlock_pre
%! unlock post vop_unlock_post
vop_unlock {
IN struct vnode *vp;
IN int flags;
};
%% bmap vp L L L
vop_bmap {
IN struct vnode *vp;
IN daddr_t bn;
OUT struct bufobj **bop;
IN daddr_t *bnp;
OUT int *runp;
OUT int *runb;
};
%% strategy vp L L L
%! strategy pre vop_strategy_pre
vop_strategy {
IN struct vnode *vp;
IN struct buf *bp;
};
%% getwritemount vp = = =
vop_getwritemount {
IN struct vnode *vp;
OUT struct mount **mpp;
};
%% print vp - - -
vop_print {
IN struct vnode *vp;
};
%% pathconf vp L L L
vop_pathconf {
IN struct vnode *vp;
IN int name;
OUT long *retval;
};
%% advlock vp U U U
vop_advlock {
IN struct vnode *vp;
IN void *id;
IN int op;
IN struct flock *fl;
IN int flags;
};
%% advlockasync vp U U U
vop_advlockasync {
IN struct vnode *vp;
IN void *id;
IN int op;
IN struct flock *fl;
IN int flags;
IN struct task *task;
INOUT void **cookiep;
};
%% advlockpurge vp E E E
vop_advlockpurge {
IN struct vnode *vp;
};
%% reallocblks vp E E E
vop_reallocblks {
IN struct vnode *vp;
IN struct cluster_save *buflist;
};
%% getpages vp L L L
vop_getpages {
IN struct vnode *vp;
IN vm_page_t *m;
IN int count;
IN int *rbehind;
IN int *rahead;
};
%% getpages_async vp L L L
vop_getpages_async {
IN struct vnode *vp;
IN vm_page_t *m;
IN int count;
IN int *rbehind;
IN int *rahead;
IN vop_getpages_iodone_t *iodone;
IN void *arg;
};
%% putpages vp L L L
vop_putpages {
IN struct vnode *vp;
IN vm_page_t *m;
IN int count;
IN int sync;
IN int *rtvals;
};
%% getacl vp L L L
vop_getacl {
IN struct vnode *vp;
IN acl_type_t type;
OUT struct acl *aclp;
IN struct ucred *cred;
IN struct thread *td;
};
%% setacl vp E E E
vop_setacl {
IN struct vnode *vp;
IN acl_type_t type;
IN struct acl *aclp;
IN struct ucred *cred;
IN struct thread *td;
};
%% aclcheck vp = = =
vop_aclcheck {
IN struct vnode *vp;
IN acl_type_t type;
IN struct acl *aclp;
IN struct ucred *cred;
IN struct thread *td;
};
%% closeextattr vp L L L
vop_closeextattr {
IN struct vnode *vp;
IN int commit;
IN struct ucred *cred;
IN struct thread *td;
};
%% getextattr vp L L L
vop_getextattr {
IN struct vnode *vp;
IN int attrnamespace;
IN const char *name;
INOUT struct uio *uio;
OUT size_t *size;
IN struct ucred *cred;
IN struct thread *td;
};
%% listextattr vp L L L
vop_listextattr {
IN struct vnode *vp;
IN int attrnamespace;
INOUT struct uio *uio;
OUT size_t *size;
IN struct ucred *cred;
IN struct thread *td;
};
%% openextattr vp L L L
vop_openextattr {
IN struct vnode *vp;
IN struct ucred *cred;
IN struct thread *td;
};
%% deleteextattr vp E E E
%! deleteextattr post vop_deleteextattr_post
vop_deleteextattr {
IN struct vnode *vp;
IN int attrnamespace;
IN const char *name;
IN struct ucred *cred;
IN struct thread *td;
};
%% setextattr vp E E E
%! setextattr post vop_setextattr_post
vop_setextattr {
IN struct vnode *vp;
IN int attrnamespace;
IN const char *name;
INOUT struct uio *uio;
IN struct ucred *cred;
IN struct thread *td;
};
%% setlabel vp E E E
vop_setlabel {
IN struct vnode *vp;
IN struct label *label;
IN struct ucred *cred;
IN struct thread *td;
};
%% vptofh vp = = =
vop_vptofh {
IN struct vnode *vp;
IN struct fid *fhp;
};
%% vptocnp vp L L L
%% vptocnp vpp - U -
vop_vptocnp {
IN struct vnode *vp;
OUT struct vnode **vpp;
IN struct ucred *cred;
INOUT char *buf;
INOUT int *buflen;
};
%% allocate vp E E E
vop_allocate {
IN struct vnode *vp;
INOUT off_t *offset;
INOUT off_t *len;
};
%% advise vp U U U
vop_advise {
IN struct vnode *vp;
IN off_t start;
IN off_t end;
IN int advice;
};
%% unp_bind vp E E E
vop_unp_bind {
IN struct vnode *vp;
IN struct unpcb *unpcb;
};
%% unp_connect vp L L L
vop_unp_connect {
IN struct vnode *vp;
OUT struct unpcb **unpcb;
};
%% unp_detach vp = = =
vop_unp_detach {
IN struct vnode *vp;
};
%% is_text vp L L L
vop_is_text {
IN struct vnode *vp;
};
%% set_text vp = = =
vop_set_text {
IN struct vnode *vp;
};
%% vop_unset_text vp = = =
vop_unset_text {
IN struct vnode *vp;
};
%% add_writecount vp L L L
vop_add_writecount {
IN struct vnode *vp;
IN int inc;
};
%% fdatasync vp L L L
vop_fdatasync {
IN struct vnode *vp;
IN struct thread *td;
};
# The VOPs below are spares at the end of the table to allow new VOPs to be
# added in stable branches without breaking the KBI. New VOPs in HEAD should
# be added above these spares. When merging a new VOP to a stable branch,
# the new VOP should replace one of the spares.
vop_spare1 {
IN struct vnode *vp;
};
vop_spare2 {
IN struct vnode *vp;
};
vop_spare3 {
IN struct vnode *vp;
};
vop_spare4 {
IN struct vnode *vp;
};
vop_spare5 {
IN struct vnode *vp;
};
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