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freebsd-nq/sys/fs/deadfs/dead_vnops.c

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/* -> /*- for copyright notices, minor format tweaks as necessary
2005-01-06 18:10:42 +00:00
/*-
BSD 4.4 Lite Kernel Sources
1994-05-24 10:09:53 +00:00
* Copyright (c) 1989, 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.
* 4. 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.
*
* @(#)dead_vnops.c 8.1 (Berkeley) 6/10/93
$Id$ -> $FreeBSD$
1999-08-28 01:08:13 +00:00
* $FreeBSD$
BSD 4.4 Lite Kernel Sources
1994-05-24 10:09:53 +00:00
*/
#include <sys/param.h>
#include <sys/systm.h>
Implemented loadable VFS modules, and made most existing filesystems loadable. (NFS is a notable exception.)
1994-09-21 03:47:43 +00:00
#include <sys/kernel.h>
Don't include <sys/lock.h> in headers when only `struct simplelock' is required. Fixed everything that depended on the pollution.
1997-12-05 19:55:52 +00:00
#include <sys/lock.h>
Undo part of the tangle of having sys/lock.h and sys/mutex.h included in other "system" header files. Also help the deprecation of lockmgr.h by making it a sub-include of sys/lock.h and removing sys/lockmgr.h form kernel .c files. Sort sys/*.h includes where possible in affected files. OK'ed by: bde (with reservations)
2001-05-01 08:13:21 +00:00
#include <sys/mutex.h>
Add support for poll(2) on files. vop_nopoll() now returns POLLNVAL if one of the new poll types is requested; hopefully this will not break any existing code. (This is done so that programs have a dependable way of determining whether a filesystem supports the extended poll types or not.) The new poll types added are: POLLWRITE - file contents may have been modified POLLNLINK - file was linked, unlinked, or renamed POLLATTRIB - file's attributes may have been changed POLLEXTEND - file was extended Note that the internal operation of poll() means that it is impossible for two processes to reliably poll for the same event (this could be fixed but may not be worth it), so it is not possible to rewrite `tail -f' to use poll at this time.
1997-12-15 03:09:59 +00:00
#include <sys/poll.h>
Undo part of the tangle of having sys/lock.h and sys/mutex.h included in other "system" header files. Also help the deprecation of lockmgr.h by making it a sub-include of sys/lock.h and removing sys/lockmgr.h form kernel .c files. Sort sys/*.h includes where possible in affected files. OK'ed by: bde (with reservations)
2001-05-01 08:13:21 +00:00
#include <sys/vnode.h>
Convert lockmgr locks from using simple locks to using mutexes. Add lockdestroy() and appropriate invocations, which corresponds to lockinit() and must be called to clean up after a lockmgr lock is no longer needed.
2000-10-04 01:29:17 +00:00
BSD 4.4 Lite Kernel Sources
1994-05-24 10:09:53 +00:00
/*
* Prototypes for dead operations on vnodes.
*/
Mechanically change prototypes for vnode operations to use the new typedefs.
2004-12-01 12:24:41 +00:00
static vop_lookup_t dead_lookup;
static vop_open_t dead_open;
- Deadfs should not use the std GETWRITEMOUNT routine. Add one that always returns NULL. MFC After: 1 week
2006-02-22 06:11:59 +00:00
static vop_getwritemount_t dead_getwritemount;
Below is slightly edited description of the LOR by Tor Egge: -------------------------- [Deadlock] is caused by a lock order reversal in vfs_lookup(), where [some] process is trying to lock a directory vnode, that is the parent directory of covered vnode) while holding an exclusive vnode lock on covering vnode. A simplified scenario: root fs var fs / A / (/var) D /var B /log (/var/log) E vfs lock C vfs lock F Within each file system, the lock order is clear: C->A->B and F->D->E When traversing across mounts, the system can choose between two lock orders, but everything must then follow that lock order: L1: C->A->B | +->F->D->E L2: F->D->E | +->C->A->B The lookup() process for namei("/var") mixes those two lock orders: VOP_LOOKUP() obtains B while A is held vfs_busy() obtains a shared lock on F while A and B are held (follows L1, violates L2) vput() releases lock on B VOP_UNLOCK() releases lock on A VFS_ROOT() obtains lock on D while shared lock on F is held vfs_unbusy() releases shared lock on F vn_lock() obtains lock on A while D is held (violates L1, follows L2) dounmount() follows L1 (B is locked while F is drained). Without unmount activity, vfs_busy() will always succeed without blocking and the deadlock isn't triggered (the system behaves as if L2 is followed). With unmount, you can get 4 processes in a deadlock: p1: holds D, want A (in lookup()) p2: holds shared lock on F, want D (in VFS_ROOT()) p3: holds B, want drain lock on F (in dounmount()) p4: holds A, want B (in VOP_LOOKUP()) You can have more than one instance of p2. The reversal was introduced in revision 1.81 of src/sys/kern/vfs_lookup.c and MFCed to revision 1.80.2.1, probably to avoid a cascade of vnode locks when nfs servers are dead (VFS_ROOT() just hangs) spreading to the root fs root vnode. - Tor Egge To fix the LOR, ups@ noted that when crossing the mount point, ni_dvp is actually not used by the callers of namei. Thus, placeholder deadfs vnode vp_crossmp is introduced that is filled into ni_dvp. Idea by: ups Reviewed by: tegge, ups, jeff, rwatson (mac interaction) Tested by: Peter Holm MFC after: 2 weeks
2007-01-22 11:25:22 +00:00
static vop_rename_t dead_rename;
BSD 4.4 Lite Kernel Sources
1994-05-24 10:09:53 +00:00
Back when VOP_* was introduced, we did not have new-style struct initializations but we did have lofty goals and big ideals. Adjust to more contemporary circumstances and gain type checking. Replace the entire vop_t frobbing thing with properly typed structures. The only casualty is that we can not add a new VOP_ method with a loadable module. History has not given us reason to belive this would ever be feasible in the the first place. Eliminate in toto VOCALL(), vop_t, VNODEOP_SET() etc. Give coda correct prototypes and function definitions for all vop_()s. Generate a bit more data from the vnode_if.src file: a struct vop_vector and protype typedefs for all vop methods. Add a new vop_bypass() and make vop_default be a pointer to another struct vop_vector. Remove a lot of vfs_init since vop_vector is ready to use from the compiler. Cast various vop_mumble() to void * with uppercase name, for instance VOP_PANIC, VOP_NULL etc. Implement VCALL() by making vdesc_offset the offsetof() the relevant function pointer in vop_vector. This is disgusting but since the code is generated by a script comparatively safe. The alternative for nullfs etc. would be much worse. Fix up all vnode method vectors to remove casts so they become typesafe. (The bulk of this is generated by scripts)
2004-12-01 23:16:38 +00:00
struct vop_vector dead_vnodeops = {
.vop_default = &default_vnodeops,
Whitespace in vop_vector{} initializations.
2005-01-13 18:59:48 +00:00
Back when VOP_* was introduced, we did not have new-style struct initializations but we did have lofty goals and big ideals. Adjust to more contemporary circumstances and gain type checking. Replace the entire vop_t frobbing thing with properly typed structures. The only casualty is that we can not add a new VOP_ method with a loadable module. History has not given us reason to belive this would ever be feasible in the the first place. Eliminate in toto VOCALL(), vop_t, VNODEOP_SET() etc. Give coda correct prototypes and function definitions for all vop_()s. Generate a bit more data from the vnode_if.src file: a struct vop_vector and protype typedefs for all vop methods. Add a new vop_bypass() and make vop_default be a pointer to another struct vop_vector. Remove a lot of vfs_init since vop_vector is ready to use from the compiler. Cast various vop_mumble() to void * with uppercase name, for instance VOP_PANIC, VOP_NULL etc. Implement VCALL() by making vdesc_offset the offsetof() the relevant function pointer in vop_vector. This is disgusting but since the code is generated by a script comparatively safe. The alternative for nullfs etc. would be much worse. Fix up all vnode method vectors to remove casts so they become typesafe. (The bulk of this is generated by scripts)
2004-12-01 23:16:38 +00:00
.vop_access = VOP_EBADF,
.vop_advlock = VOP_EBADF,
The deadfs VOPs for vop_ioctl and vop_bmap call itself recursively, which is an elaborate way to cause kernel panic. Change the VOPs implementation to return EBADF for a reclaimed vnode. While the calls to vop_bmap should not reach deadfs, it is indeed possible for vop_ioctl, because the VOP locking protocol is to pass the vnode to VOP unlocked. The actual panic was observed when ioctl was called on procfs filedescriptor which pointed to an exited process. Reported by: zont Tested by: pho MFC after: 1 week
2012-09-13 13:05:45 +00:00
.vop_bmap = VOP_EBADF,
Back when VOP_* was introduced, we did not have new-style struct initializations but we did have lofty goals and big ideals. Adjust to more contemporary circumstances and gain type checking. Replace the entire vop_t frobbing thing with properly typed structures. The only casualty is that we can not add a new VOP_ method with a loadable module. History has not given us reason to belive this would ever be feasible in the the first place. Eliminate in toto VOCALL(), vop_t, VNODEOP_SET() etc. Give coda correct prototypes and function definitions for all vop_()s. Generate a bit more data from the vnode_if.src file: a struct vop_vector and protype typedefs for all vop methods. Add a new vop_bypass() and make vop_default be a pointer to another struct vop_vector. Remove a lot of vfs_init since vop_vector is ready to use from the compiler. Cast various vop_mumble() to void * with uppercase name, for instance VOP_PANIC, VOP_NULL etc. Implement VCALL() by making vdesc_offset the offsetof() the relevant function pointer in vop_vector. This is disgusting but since the code is generated by a script comparatively safe. The alternative for nullfs etc. would be much worse. Fix up all vnode method vectors to remove casts so they become typesafe. (The bulk of this is generated by scripts)
2004-12-01 23:16:38 +00:00
.vop_create = VOP_PANIC,
.vop_getattr = VOP_EBADF,
- Deadfs should not use the std GETWRITEMOUNT routine. Add one that always returns NULL. MFC After: 1 week
2006-02-22 06:11:59 +00:00
.vop_getwritemount = dead_getwritemount,
Back when VOP_* was introduced, we did not have new-style struct initializations but we did have lofty goals and big ideals. Adjust to more contemporary circumstances and gain type checking. Replace the entire vop_t frobbing thing with properly typed structures. The only casualty is that we can not add a new VOP_ method with a loadable module. History has not given us reason to belive this would ever be feasible in the the first place. Eliminate in toto VOCALL(), vop_t, VNODEOP_SET() etc. Give coda correct prototypes and function definitions for all vop_()s. Generate a bit more data from the vnode_if.src file: a struct vop_vector and protype typedefs for all vop methods. Add a new vop_bypass() and make vop_default be a pointer to another struct vop_vector. Remove a lot of vfs_init since vop_vector is ready to use from the compiler. Cast various vop_mumble() to void * with uppercase name, for instance VOP_PANIC, VOP_NULL etc. Implement VCALL() by making vdesc_offset the offsetof() the relevant function pointer in vop_vector. This is disgusting but since the code is generated by a script comparatively safe. The alternative for nullfs etc. would be much worse. Fix up all vnode method vectors to remove casts so they become typesafe. (The bulk of this is generated by scripts)
2004-12-01 23:16:38 +00:00
.vop_inactive = VOP_NULL,
The deadfs VOPs for vop_ioctl and vop_bmap call itself recursively, which is an elaborate way to cause kernel panic. Change the VOPs implementation to return EBADF for a reclaimed vnode. While the calls to vop_bmap should not reach deadfs, it is indeed possible for vop_ioctl, because the VOP locking protocol is to pass the vnode to VOP unlocked. The actual panic was observed when ioctl was called on procfs filedescriptor which pointed to an exited process. Reported by: zont Tested by: pho MFC after: 1 week
2012-09-13 13:05:45 +00:00
.vop_ioctl = VOP_EBADF,
Back when VOP_* was introduced, we did not have new-style struct initializations but we did have lofty goals and big ideals. Adjust to more contemporary circumstances and gain type checking. Replace the entire vop_t frobbing thing with properly typed structures. The only casualty is that we can not add a new VOP_ method with a loadable module. History has not given us reason to belive this would ever be feasible in the the first place. Eliminate in toto VOCALL(), vop_t, VNODEOP_SET() etc. Give coda correct prototypes and function definitions for all vop_()s. Generate a bit more data from the vnode_if.src file: a struct vop_vector and protype typedefs for all vop methods. Add a new vop_bypass() and make vop_default be a pointer to another struct vop_vector. Remove a lot of vfs_init since vop_vector is ready to use from the compiler. Cast various vop_mumble() to void * with uppercase name, for instance VOP_PANIC, VOP_NULL etc. Implement VCALL() by making vdesc_offset the offsetof() the relevant function pointer in vop_vector. This is disgusting but since the code is generated by a script comparatively safe. The alternative for nullfs etc. would be much worse. Fix up all vnode method vectors to remove casts so they become typesafe. (The bulk of this is generated by scripts)
2004-12-01 23:16:38 +00:00
.vop_link = VOP_PANIC,
.vop_lookup = dead_lookup,
.vop_mkdir = VOP_PANIC,
.vop_mknod = VOP_PANIC,
.vop_open = dead_open,
.vop_pathconf = VOP_EBADF, /* per pathconf(2) */
.vop_poll = dead_poll,
.vop_read = dead_read,
.vop_readdir = VOP_EBADF,
.vop_readlink = VOP_EBADF,
.vop_reclaim = VOP_NULL,
.vop_remove = VOP_PANIC,
Below is slightly edited description of the LOR by Tor Egge: -------------------------- [Deadlock] is caused by a lock order reversal in vfs_lookup(), where [some] process is trying to lock a directory vnode, that is the parent directory of covered vnode) while holding an exclusive vnode lock on covering vnode. A simplified scenario: root fs var fs / A / (/var) D /var B /log (/var/log) E vfs lock C vfs lock F Within each file system, the lock order is clear: C->A->B and F->D->E When traversing across mounts, the system can choose between two lock orders, but everything must then follow that lock order: L1: C->A->B | +->F->D->E L2: F->D->E | +->C->A->B The lookup() process for namei("/var") mixes those two lock orders: VOP_LOOKUP() obtains B while A is held vfs_busy() obtains a shared lock on F while A and B are held (follows L1, violates L2) vput() releases lock on B VOP_UNLOCK() releases lock on A VFS_ROOT() obtains lock on D while shared lock on F is held vfs_unbusy() releases shared lock on F vn_lock() obtains lock on A while D is held (violates L1, follows L2) dounmount() follows L1 (B is locked while F is drained). Without unmount activity, vfs_busy() will always succeed without blocking and the deadlock isn't triggered (the system behaves as if L2 is followed). With unmount, you can get 4 processes in a deadlock: p1: holds D, want A (in lookup()) p2: holds shared lock on F, want D (in VFS_ROOT()) p3: holds B, want drain lock on F (in dounmount()) p4: holds A, want B (in VOP_LOOKUP()) You can have more than one instance of p2. The reversal was introduced in revision 1.81 of src/sys/kern/vfs_lookup.c and MFCed to revision 1.80.2.1, probably to avoid a cascade of vnode locks when nfs servers are dead (VFS_ROOT() just hangs) spreading to the root fs root vnode. - Tor Egge To fix the LOR, ups@ noted that when crossing the mount point, ni_dvp is actually not used by the callers of namei. Thus, placeholder deadfs vnode vp_crossmp is introduced that is filled into ni_dvp. Idea by: ups Reviewed by: tegge, ups, jeff, rwatson (mac interaction) Tested by: Peter Holm MFC after: 2 weeks
2007-01-22 11:25:22 +00:00
.vop_rename = dead_rename,
Back when VOP_* was introduced, we did not have new-style struct initializations but we did have lofty goals and big ideals. Adjust to more contemporary circumstances and gain type checking. Replace the entire vop_t frobbing thing with properly typed structures. The only casualty is that we can not add a new VOP_ method with a loadable module. History has not given us reason to belive this would ever be feasible in the the first place. Eliminate in toto VOCALL(), vop_t, VNODEOP_SET() etc. Give coda correct prototypes and function definitions for all vop_()s. Generate a bit more data from the vnode_if.src file: a struct vop_vector and protype typedefs for all vop methods. Add a new vop_bypass() and make vop_default be a pointer to another struct vop_vector. Remove a lot of vfs_init since vop_vector is ready to use from the compiler. Cast various vop_mumble() to void * with uppercase name, for instance VOP_PANIC, VOP_NULL etc. Implement VCALL() by making vdesc_offset the offsetof() the relevant function pointer in vop_vector. This is disgusting but since the code is generated by a script comparatively safe. The alternative for nullfs etc. would be much worse. Fix up all vnode method vectors to remove casts so they become typesafe. (The bulk of this is generated by scripts)
2004-12-01 23:16:38 +00:00
.vop_rmdir = VOP_PANIC,
.vop_setattr = VOP_EBADF,
.vop_symlink = VOP_PANIC,
Add a simple VOP_VPTOCNP implementation for deadfs which returns EBADF. Reviewed by: arch Approved by: kib
2008-12-12 00:59:36 +00:00
.vop_vptocnp = VOP_EBADF,
Back when VOP_* was introduced, we did not have new-style struct initializations but we did have lofty goals and big ideals. Adjust to more contemporary circumstances and gain type checking. Replace the entire vop_t frobbing thing with properly typed structures. The only casualty is that we can not add a new VOP_ method with a loadable module. History has not given us reason to belive this would ever be feasible in the the first place. Eliminate in toto VOCALL(), vop_t, VNODEOP_SET() etc. Give coda correct prototypes and function definitions for all vop_()s. Generate a bit more data from the vnode_if.src file: a struct vop_vector and protype typedefs for all vop methods. Add a new vop_bypass() and make vop_default be a pointer to another struct vop_vector. Remove a lot of vfs_init since vop_vector is ready to use from the compiler. Cast various vop_mumble() to void * with uppercase name, for instance VOP_PANIC, VOP_NULL etc. Implement VCALL() by making vdesc_offset the offsetof() the relevant function pointer in vop_vector. This is disgusting but since the code is generated by a script comparatively safe. The alternative for nullfs etc. would be much worse. Fix up all vnode method vectors to remove casts so they become typesafe. (The bulk of this is generated by scripts)
2004-12-01 23:16:38 +00:00
.vop_write = dead_write,
BSD 4.4 Lite Kernel Sources
1994-05-24 10:09:53 +00:00
};
Implemented loadable VFS modules, and made most existing filesystems loadable. (NFS is a notable exception.)
1994-09-21 03:47:43 +00:00
- Deadfs should not use the std GETWRITEMOUNT routine. Add one that always returns NULL. MFC After: 1 week
2006-02-22 06:11:59 +00:00
static int
Style changes for deadfs: - ANSIfy VOPs. - Remove trivial comments. - Remove ARGSUSED. - Remove copies of the vop_XXX_args structure definitions in comments. Sponsored by: The FreeBSD Foundation MFC after: 1 week
2014-10-15 13:22:33 +00:00
dead_getwritemount(struct vop_getwritemount_args *ap)
- Deadfs should not use the std GETWRITEMOUNT routine. Add one that always returns NULL. MFC After: 1 week
2006-02-22 06:11:59 +00:00
{
Style changes for deadfs: - ANSIfy VOPs. - Remove trivial comments. - Remove ARGSUSED. - Remove copies of the vop_XXX_args structure definitions in comments. Sponsored by: The FreeBSD Foundation MFC after: 1 week
2014-10-15 13:22:33 +00:00
- Deadfs should not use the std GETWRITEMOUNT routine. Add one that always returns NULL. MFC After: 1 week
2006-02-22 06:11:59 +00:00
*(ap->a_mpp) = NULL;
return (0);
}
BSD 4.4 Lite Kernel Sources
1994-05-24 10:09:53 +00:00
/*
* Trivial lookup routine that always fails.
*/
staticize.
1995-12-02 17:14:34 +00:00
static int
Style changes for deadfs: - ANSIfy VOPs. - Remove trivial comments. - Remove ARGSUSED. - Remove copies of the vop_XXX_args structure definitions in comments. Sponsored by: The FreeBSD Foundation MFC after: 1 week
2014-10-15 13:22:33 +00:00
dead_lookup(struct vop_lookup_args *ap)
BSD 4.4 Lite Kernel Sources
1994-05-24 10:09:53 +00:00
{
*ap->a_vpp = NULL;
return (ENOTDIR);
}
/*
* Open always fails as if device did not exist.
*/
staticize.
1995-12-02 17:14:34 +00:00
static int
Style changes for deadfs: - ANSIfy VOPs. - Remove trivial comments. - Remove ARGSUSED. - Remove copies of the vop_XXX_args structure definitions in comments. Sponsored by: The FreeBSD Foundation MFC after: 1 week
2014-10-15 13:22:33 +00:00
dead_open(struct vop_open_args *ap)
BSD 4.4 Lite Kernel Sources
1994-05-24 10:09:53 +00:00
{
return (ENXIO);
}
When vnode bypass cannot be performed on the cdev file descriptor for read/write/poll/ioctl, call standard vnode filedescriptor fop. This restores the special handling for terminals by calling the deadfs VOP, instead of always returning ENXIO for destroyed devices or revoked terminals. Since destroyed (and not revoked) device would use devfs_specops VOP vector, make dead_read/write/poll non-static and fill VOP table with pointers to the functions, to instead of VOP_PANIC. Noted and reviewed by: bde Sponsored by: The FreeBSD Foundation MFC after: 1 week
2014-10-15 13:16:51 +00:00
int
Style changes for deadfs: - ANSIfy VOPs. - Remove trivial comments. - Remove ARGSUSED. - Remove copies of the vop_XXX_args structure definitions in comments. Sponsored by: The FreeBSD Foundation MFC after: 1 week
2014-10-15 13:22:33 +00:00
dead_read(struct vop_read_args *ap)
BSD 4.4 Lite Kernel Sources
1994-05-24 10:09:53 +00:00
{
Style changes for deadfs: - ANSIfy VOPs. - Remove trivial comments. - Remove ARGSUSED. - Remove copies of the vop_XXX_args structure definitions in comments. Sponsored by: The FreeBSD Foundation MFC after: 1 week
2014-10-15 13:22:33 +00:00
This is the kernel Lite/2 commit. There are some requisite userland changes, so don't expect to be able to run the kernel as-is (very well) without the appropriate Lite/2 userland changes. The system boots and can mount UFS filesystems. Untested: ext2fs, msdosfs, NFS Known problems: Incorrect Berkeley ID strings in some files. Mount_std mounts will not work until the getfsent library routine is changed. Reviewed by: various people Submitted by: Jeffery Hsu <hsu@freebsd.org>
1997-02-10 02:22:35 +00:00
/*
* Return EOF for tty devices, EIO for others
*/
- Replace v_flag with v_iflag and v_vflag - v_vflag is protected by the vnode lock and is used when synchronization with VOP calls is needed. - v_iflag is protected by interlock and is used for dealing with vnode management issues. These flags include X/O LOCK, FREE, DOOMED, etc. - All accesses to v_iflag and v_vflag have either been locked or marked with mp_fixme's. - Many ASSERT_VOP_LOCKED calls have been added where the locking was not clear. - Many functions in vfs_subr.c were restructured to provide for stronger locking. Idea stolen from: BSD/OS
2002-08-04 10:29:36 +00:00
if ((ap->a_vp->v_vflag & VV_ISTTY) == 0)
This is the kernel Lite/2 commit. There are some requisite userland changes, so don't expect to be able to run the kernel as-is (very well) without the appropriate Lite/2 userland changes. The system boots and can mount UFS filesystems. Untested: ext2fs, msdosfs, NFS Known problems: Incorrect Berkeley ID strings in some files. Mount_std mounts will not work until the getfsent library routine is changed. Reviewed by: various people Submitted by: Jeffery Hsu <hsu@freebsd.org>
1997-02-10 02:22:35 +00:00
return (EIO);
BSD 4.4 Lite Kernel Sources
1994-05-24 10:09:53 +00:00
return (0);
}
When vnode bypass cannot be performed on the cdev file descriptor for read/write/poll/ioctl, call standard vnode filedescriptor fop. This restores the special handling for terminals by calling the deadfs VOP, instead of always returning ENXIO for destroyed devices or revoked terminals. Since destroyed (and not revoked) device would use devfs_specops VOP vector, make dead_read/write/poll non-static and fill VOP table with pointers to the functions, to instead of VOP_PANIC. Noted and reviewed by: bde Sponsored by: The FreeBSD Foundation MFC after: 1 week
2014-10-15 13:16:51 +00:00
int
Style changes for deadfs: - ANSIfy VOPs. - Remove trivial comments. - Remove ARGSUSED. - Remove copies of the vop_XXX_args structure definitions in comments. Sponsored by: The FreeBSD Foundation MFC after: 1 week
2014-10-15 13:22:33 +00:00
dead_write(struct vop_write_args *ap)
BSD 4.4 Lite Kernel Sources
1994-05-24 10:09:53 +00:00
{
Style changes for deadfs: - ANSIfy VOPs. - Remove trivial comments. - Remove ARGSUSED. - Remove copies of the vop_XXX_args structure definitions in comments. Sponsored by: The FreeBSD Foundation MFC after: 1 week
2014-10-15 13:22:33 +00:00
BSD 4.4 Lite Kernel Sources
1994-05-24 10:09:53 +00:00
return (EIO);
}
When vnode bypass cannot be performed on the cdev file descriptor for read/write/poll/ioctl, call standard vnode filedescriptor fop. This restores the special handling for terminals by calling the deadfs VOP, instead of always returning ENXIO for destroyed devices or revoked terminals. Since destroyed (and not revoked) device would use devfs_specops VOP vector, make dead_read/write/poll non-static and fill VOP table with pointers to the functions, to instead of VOP_PANIC. Noted and reviewed by: bde Sponsored by: The FreeBSD Foundation MFC after: 1 week
2014-10-15 13:16:51 +00:00
int
Style changes for deadfs: - ANSIfy VOPs. - Remove trivial comments. - Remove ARGSUSED. - Remove copies of the vop_XXX_args structure definitions in comments. Sponsored by: The FreeBSD Foundation MFC after: 1 week
2014-10-15 13:22:33 +00:00
dead_poll(struct vop_poll_args *ap)
Add support for poll(2) on files. vop_nopoll() now returns POLLNVAL if one of the new poll types is requested; hopefully this will not break any existing code. (This is done so that programs have a dependable way of determining whether a filesystem supports the extended poll types or not.) The new poll types added are: POLLWRITE - file contents may have been modified POLLNLINK - file was linked, unlinked, or renamed POLLATTRIB - file's attributes may have been changed POLLEXTEND - file was extended Note that the internal operation of poll() means that it is impossible for two processes to reliably poll for the same event (this could be fixed but may not be worth it), so it is not possible to rewrite `tail -f' to use poll at this time.
1997-12-15 03:09:59 +00:00
{
Change the deadfs poll VOP to return POLLIN|POLLRDNORM if the caller is interested in i/o state. Return POLLNVAL for invalid bits, similar to poll_no_poll(). Note that POLLOUT must not be returned, since POLLHUP is set. Noted and reviewed by: bde Sponsored by: The FreeBSD Foundation MFC after: 1 week
2014-10-15 13:08:53 +00:00
if (ap->a_events & ~POLLSTANDARD)
return (POLLNVAL);
/*
* Let the user find out that the descriptor is gone.
*/
return (POLLHUP | ((POLLIN | POLLRDNORM) & ap->a_events));
Add support for poll(2) on files. vop_nopoll() now returns POLLNVAL if one of the new poll types is requested; hopefully this will not break any existing code. (This is done so that programs have a dependable way of determining whether a filesystem supports the extended poll types or not.) The new poll types added are: POLLWRITE - file contents may have been modified POLLNLINK - file was linked, unlinked, or renamed POLLATTRIB - file's attributes may have been changed POLLEXTEND - file was extended Note that the internal operation of poll() means that it is impossible for two processes to reliably poll for the same event (this could be fixed but may not be worth it), so it is not possible to rewrite `tail -f' to use poll at this time.
1997-12-15 03:09:59 +00:00
}
Below is slightly edited description of the LOR by Tor Egge: -------------------------- [Deadlock] is caused by a lock order reversal in vfs_lookup(), where [some] process is trying to lock a directory vnode, that is the parent directory of covered vnode) while holding an exclusive vnode lock on covering vnode. A simplified scenario: root fs var fs / A / (/var) D /var B /log (/var/log) E vfs lock C vfs lock F Within each file system, the lock order is clear: C->A->B and F->D->E When traversing across mounts, the system can choose between two lock orders, but everything must then follow that lock order: L1: C->A->B | +->F->D->E L2: F->D->E | +->C->A->B The lookup() process for namei("/var") mixes those two lock orders: VOP_LOOKUP() obtains B while A is held vfs_busy() obtains a shared lock on F while A and B are held (follows L1, violates L2) vput() releases lock on B VOP_UNLOCK() releases lock on A VFS_ROOT() obtains lock on D while shared lock on F is held vfs_unbusy() releases shared lock on F vn_lock() obtains lock on A while D is held (violates L1, follows L2) dounmount() follows L1 (B is locked while F is drained). Without unmount activity, vfs_busy() will always succeed without blocking and the deadlock isn't triggered (the system behaves as if L2 is followed). With unmount, you can get 4 processes in a deadlock: p1: holds D, want A (in lookup()) p2: holds shared lock on F, want D (in VFS_ROOT()) p3: holds B, want drain lock on F (in dounmount()) p4: holds A, want B (in VOP_LOOKUP()) You can have more than one instance of p2. The reversal was introduced in revision 1.81 of src/sys/kern/vfs_lookup.c and MFCed to revision 1.80.2.1, probably to avoid a cascade of vnode locks when nfs servers are dead (VFS_ROOT() just hangs) spreading to the root fs root vnode. - Tor Egge To fix the LOR, ups@ noted that when crossing the mount point, ni_dvp is actually not used by the callers of namei. Thus, placeholder deadfs vnode vp_crossmp is introduced that is filled into ni_dvp. Idea by: ups Reviewed by: tegge, ups, jeff, rwatson (mac interaction) Tested by: Peter Holm MFC after: 2 weeks
2007-01-22 11:25:22 +00:00
static int
Style changes for deadfs: - ANSIfy VOPs. - Remove trivial comments. - Remove ARGSUSED. - Remove copies of the vop_XXX_args structure definitions in comments. Sponsored by: The FreeBSD Foundation MFC after: 1 week
2014-10-15 13:22:33 +00:00
dead_rename(struct vop_rename_args *ap)
Below is slightly edited description of the LOR by Tor Egge: -------------------------- [Deadlock] is caused by a lock order reversal in vfs_lookup(), where [some] process is trying to lock a directory vnode, that is the parent directory of covered vnode) while holding an exclusive vnode lock on covering vnode. A simplified scenario: root fs var fs / A / (/var) D /var B /log (/var/log) E vfs lock C vfs lock F Within each file system, the lock order is clear: C->A->B and F->D->E When traversing across mounts, the system can choose between two lock orders, but everything must then follow that lock order: L1: C->A->B | +->F->D->E L2: F->D->E | +->C->A->B The lookup() process for namei("/var") mixes those two lock orders: VOP_LOOKUP() obtains B while A is held vfs_busy() obtains a shared lock on F while A and B are held (follows L1, violates L2) vput() releases lock on B VOP_UNLOCK() releases lock on A VFS_ROOT() obtains lock on D while shared lock on F is held vfs_unbusy() releases shared lock on F vn_lock() obtains lock on A while D is held (violates L1, follows L2) dounmount() follows L1 (B is locked while F is drained). Without unmount activity, vfs_busy() will always succeed without blocking and the deadlock isn't triggered (the system behaves as if L2 is followed). With unmount, you can get 4 processes in a deadlock: p1: holds D, want A (in lookup()) p2: holds shared lock on F, want D (in VFS_ROOT()) p3: holds B, want drain lock on F (in dounmount()) p4: holds A, want B (in VOP_LOOKUP()) You can have more than one instance of p2. The reversal was introduced in revision 1.81 of src/sys/kern/vfs_lookup.c and MFCed to revision 1.80.2.1, probably to avoid a cascade of vnode locks when nfs servers are dead (VFS_ROOT() just hangs) spreading to the root fs root vnode. - Tor Egge To fix the LOR, ups@ noted that when crossing the mount point, ni_dvp is actually not used by the callers of namei. Thus, placeholder deadfs vnode vp_crossmp is introduced that is filled into ni_dvp. Idea by: ups Reviewed by: tegge, ups, jeff, rwatson (mac interaction) Tested by: Peter Holm MFC after: 2 weeks
2007-01-22 11:25:22 +00:00
{
Add function vop_rename_fail(9) that performs needed cleanup for locks and references of the VOP_RENAME(9) arguments. Use vop_rename_fail() in deadfs_rename(). Tested by: Mikolaj Golub MFC after: 1 week
2010-04-02 14:03:01 +00:00
vop_rename_fail(ap);
Below is slightly edited description of the LOR by Tor Egge: -------------------------- [Deadlock] is caused by a lock order reversal in vfs_lookup(), where [some] process is trying to lock a directory vnode, that is the parent directory of covered vnode) while holding an exclusive vnode lock on covering vnode. A simplified scenario: root fs var fs / A / (/var) D /var B /log (/var/log) E vfs lock C vfs lock F Within each file system, the lock order is clear: C->A->B and F->D->E When traversing across mounts, the system can choose between two lock orders, but everything must then follow that lock order: L1: C->A->B | +->F->D->E L2: F->D->E | +->C->A->B The lookup() process for namei("/var") mixes those two lock orders: VOP_LOOKUP() obtains B while A is held vfs_busy() obtains a shared lock on F while A and B are held (follows L1, violates L2) vput() releases lock on B VOP_UNLOCK() releases lock on A VFS_ROOT() obtains lock on D while shared lock on F is held vfs_unbusy() releases shared lock on F vn_lock() obtains lock on A while D is held (violates L1, follows L2) dounmount() follows L1 (B is locked while F is drained). Without unmount activity, vfs_busy() will always succeed without blocking and the deadlock isn't triggered (the system behaves as if L2 is followed). With unmount, you can get 4 processes in a deadlock: p1: holds D, want A (in lookup()) p2: holds shared lock on F, want D (in VFS_ROOT()) p3: holds B, want drain lock on F (in dounmount()) p4: holds A, want B (in VOP_LOOKUP()) You can have more than one instance of p2. The reversal was introduced in revision 1.81 of src/sys/kern/vfs_lookup.c and MFCed to revision 1.80.2.1, probably to avoid a cascade of vnode locks when nfs servers are dead (VFS_ROOT() just hangs) spreading to the root fs root vnode. - Tor Egge To fix the LOR, ups@ noted that when crossing the mount point, ni_dvp is actually not used by the callers of namei. Thus, placeholder deadfs vnode vp_crossmp is introduced that is filled into ni_dvp. Idea by: ups Reviewed by: tegge, ups, jeff, rwatson (mac interaction) Tested by: Peter Holm MFC after: 2 weeks
2007-01-22 11:25:22 +00:00
return (EXDEV);
}
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