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Use vn_io_fault for the writes from core dumping code. Recursing into

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VM due to copyin(9) faulting while VFS locks are held is
deadlock-prone there in the same way as for the write(2) syscall.

Reported and tested by:	pho
Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks
This commit is contained in:
Konstantin Belousov 2014-06-15 04:51:53 +00:00
parent c1a08643e3
commit 2e501b0a9e
1 changed files with 137 additions and 52 deletions
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189
sys/kern/vfs_vnops.c
View File

@ -8,7 +8,7 @@
* the permission of UNIX System Laboratories, Inc.
*
* Copyright (c) 2012 Konstantin Belousov <kib@FreeBSD.org>
* Copyright (c) 2013 The FreeBSD Foundation
* Copyright (c) 2013, 2014 The FreeBSD Foundation
*
* Portions of this software were developed by Konstantin Belousov
* under sponsorship from the FreeBSD Foundation.
@ -106,6 +106,53 @@ struct fileops vnops = {
.fo_flags = DFLAG_PASSABLE | DFLAG_SEEKABLE
};
static const int io_hold_cnt = 16;
static int vn_io_fault_enable = 1;
SYSCTL_INT(_debug, OID_AUTO, vn_io_fault_enable, CTLFLAG_RW,
&vn_io_fault_enable, 0, "Enable vn_io_fault lock avoidance");
static u_long vn_io_faults_cnt;
SYSCTL_ULONG(_debug, OID_AUTO, vn_io_faults, CTLFLAG_RD,
&vn_io_faults_cnt, 0, "Count of vn_io_fault lock avoidance triggers");
/*
* Returns true if vn_io_fault mode of handling the i/o request should
* be used.
*/
static bool
do_vn_io_fault(struct vnode *vp, struct uio *uio)
{
struct mount *mp;
return (uio->uio_segflg == UIO_USERSPACE && vp->v_type == VREG &&
(mp = vp->v_mount) != NULL &&
(mp->mnt_kern_flag & MNTK_NO_IOPF) != 0 && vn_io_fault_enable);
}
/*
* Structure used to pass arguments to vn_io_fault1(), to do either
* file- or vnode-based I/O calls.
*/
struct vn_io_fault_args {
enum {
VN_IO_FAULT_FOP,
VN_IO_FAULT_VOP
} kind;
struct ucred *cred;
int flags;
union {
struct fop_args_tag {
struct file *fp;
fo_rdwr_t *doio;
} fop_args;
struct vop_args_tag {
struct vnode *vp;
} vop_args;
} args;
};
static int vn_io_fault1(struct vnode *vp, struct uio *uio,
struct vn_io_fault_args *args, struct thread *td);
int
vn_open(ndp, flagp, cmode, fp)
struct nameidata *ndp;
@ -439,6 +486,7 @@ vn_rdwr(enum uio_rw rw, struct vnode *vp, void *base, int len, off_t offset,
struct mount *mp;
struct ucred *cred;
void *rl_cookie;
struct vn_io_fault_args args;
int error, lock_flags;
auio.uio_iov = &aiov;
@ -493,10 +541,17 @@ vn_rdwr(enum uio_rw rw, struct vnode *vp, void *base, int len, off_t offset,
cred = file_cred;
else
cred = active_cred;
if (rw == UIO_READ)
if (do_vn_io_fault(vp, &auio)) {
args.kind = VN_IO_FAULT_VOP;
args.cred = cred;
args.flags = ioflg;
args.args.vop_args.vp = vp;
error = vn_io_fault1(vp, &auio, &args, td);
} else if (rw == UIO_READ) {
error = VOP_READ(vp, &auio, ioflg, cred);
else
} else /* if (rw == UIO_WRITE) */ {
error = VOP_WRITE(vp, &auio, ioflg, cred);
}
}
if (aresid)
*aresid = auio.uio_resid;
@ -883,14 +938,6 @@ unlock:
return (error);
}
static const int io_hold_cnt = 16;
static int vn_io_fault_enable = 1;
SYSCTL_INT(_debug, OID_AUTO, vn_io_fault_enable, CTLFLAG_RW,
&vn_io_fault_enable, 0, "Enable vn_io_fault lock avoidance");
static u_long vn_io_faults_cnt;
SYSCTL_ULONG(_debug, OID_AUTO, vn_io_faults, CTLFLAG_RD,
&vn_io_faults_cnt, 0, "Count of vn_io_fault lock avoidance triggers");
/*
* The vn_io_fault() is a wrapper around vn_read() and vn_write() to
* prevent the following deadlock:
@ -924,38 +971,55 @@ SYSCTL_ULONG(_debug, OID_AUTO, vn_io_faults, CTLFLAG_RD,
* make the current i/o request atomic with respect to other i/os and
* truncations.
*/
/*
* Decode vn_io_fault_args and perform the corresponding i/o.
*/
static int
vn_io_fault(struct file *fp, struct uio *uio, struct ucred *active_cred,
int flags, struct thread *td)
vn_io_fault_doio(struct vn_io_fault_args *args, struct uio *uio,
struct thread *td)
{
switch (args->kind) {
case VN_IO_FAULT_FOP:
return ((args->args.fop_args.doio)(args->args.fop_args.fp,
uio, args->cred, args->flags, td));
case VN_IO_FAULT_VOP:
if (uio->uio_rw == UIO_READ) {
return (VOP_READ(args->args.vop_args.vp, uio,
args->flags, args->cred));
} else if (uio->uio_rw == UIO_WRITE) {
return (VOP_WRITE(args->args.vop_args.vp, uio,
args->flags, args->cred));
}
break;
}
panic("vn_io_fault_doio: unknown kind of io %d %d", args->kind,
uio->uio_rw);
}
/*
* Common code for vn_io_fault(), agnostic to the kind of i/o request.
* Uses vn_io_fault_doio() to make the call to an actual i/o function.
* Used from vn_rdwr() and vn_io_fault(), which encode the i/o request
* into args and call vn_io_fault1() to handle faults during the user
* mode buffer accesses.
*/
static int
vn_io_fault1(struct vnode *vp, struct uio *uio, struct vn_io_fault_args *args,
struct thread *td)
{
vm_page_t ma[io_hold_cnt + 2];
struct uio *uio_clone, short_uio;
struct iovec short_iovec[1];
fo_rdwr_t *doio;
struct vnode *vp;
void *rl_cookie;
struct mount *mp;
vm_page_t *prev_td_ma;
int error, cnt, save, saveheld, prev_td_ma_cnt;
vm_offset_t addr, end;
vm_prot_t prot;
vm_offset_t addr, end;
size_t len, resid;
ssize_t adv;
int error, cnt, save, saveheld, prev_td_ma_cnt;
if (uio->uio_rw == UIO_READ)
doio = vn_read;
else
doio = vn_write;
vp = fp->f_vnode;
foffset_lock_uio(fp, uio, flags);
if (uio->uio_segflg != UIO_USERSPACE || vp->v_type != VREG ||
((mp = vp->v_mount) != NULL &&
(mp->mnt_kern_flag & MNTK_NO_IOPF) == 0) ||
!vn_io_fault_enable) {
error = doio(fp, uio, active_cred, flags | FOF_OFFSET, td);
goto out_last;
}
prot = uio->uio_rw == UIO_READ ? VM_PROT_WRITE : VM_PROT_READ;
/*
* The UFS follows IO_UNIT directive and replays back both
@ -973,22 +1037,8 @@ vn_io_fault(struct file *fp, struct uio *uio, struct ucred *active_cred,
short_uio.uio_rw = uio->uio_rw;
short_uio.uio_td = uio->uio_td;
if (uio->uio_rw == UIO_READ) {
prot = VM_PROT_WRITE;
rl_cookie = vn_rangelock_rlock(vp, uio->uio_offset,
uio->uio_offset + uio->uio_resid);
} else {
prot = VM_PROT_READ;
if ((fp->f_flag & O_APPEND) != 0 || (flags & FOF_OFFSET) == 0)
/* For appenders, punt and lock the whole range. */
rl_cookie = vn_rangelock_wlock(vp, 0, OFF_MAX);
else
rl_cookie = vn_rangelock_wlock(vp, uio->uio_offset,
uio->uio_offset + uio->uio_resid);
}
save = vm_fault_disable_pagefaults();
error = doio(fp, uio, active_cred, flags | FOF_OFFSET, td);
error = vn_io_fault_doio(args, uio, td);
if (error != EFAULT)
goto out;
@ -1038,8 +1088,7 @@ vn_io_fault(struct file *fp, struct uio *uio, struct ucred *active_cred,
td->td_ma = ma;
td->td_ma_cnt = cnt;
error = doio(fp, &short_uio, active_cred, flags | FOF_OFFSET,
td);
error = vn_io_fault_doio(args, &short_uio, td);
vm_page_unhold_pages(ma, cnt);
adv = len - short_uio.uio_resid;
@ -1060,9 +1109,45 @@ vn_io_fault(struct file *fp, struct uio *uio, struct ucred *active_cred,
curthread_pflags_restore(saveheld);
out:
vm_fault_enable_pagefaults(save);
vn_rangelock_unlock(vp, rl_cookie);
free(uio_clone, M_IOV);
out_last:
return (error);
}
static int
vn_io_fault(struct file *fp, struct uio *uio, struct ucred *active_cred,
int flags, struct thread *td)
{
fo_rdwr_t *doio;
struct vnode *vp;
void *rl_cookie;
struct vn_io_fault_args args;
int error;
doio = uio->uio_rw == UIO_READ ? vn_read : vn_write;
vp = fp->f_vnode;
foffset_lock_uio(fp, uio, flags);
if (do_vn_io_fault(vp, uio)) {
args.kind = VN_IO_FAULT_FOP;
args.args.fop_args.fp = fp;
args.args.fop_args.doio = doio;
args.cred = active_cred;
args.flags = flags | FOF_OFFSET;
if (uio->uio_rw == UIO_READ) {
rl_cookie = vn_rangelock_rlock(vp, uio->uio_offset,
uio->uio_offset + uio->uio_resid);
} else if ((fp->f_flag & O_APPEND) != 0 ||
(flags & FOF_OFFSET) == 0) {
/* For appenders, punt and lock the whole range. */
rl_cookie = vn_rangelock_wlock(vp, 0, OFF_MAX);
} else {
rl_cookie = vn_rangelock_wlock(vp, uio->uio_offset,
uio->uio_offset + uio->uio_resid);
}
error = vn_io_fault1(vp, uio, &args, td);
vn_rangelock_unlock(vp, rl_cookie);
} else {
error = doio(fp, uio, active_cred, flags | FOF_OFFSET, td);
}
foffset_unlock_uio(fp, uio, flags);
return (error);
}