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vfs: manage mnt_writeopcount with atomics

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See r352424.

Reviewed by:	kib, jeff
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
Differential Revision:	https://reviews.freebsd.org/D21575
This commit is contained in:
mjg 2019-09-16 21:33:16 +00:00
parent e19820cd96
commit 099eed319c
2 changed files with 52 additions and 14 deletions
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57
sys/kern/vfs_vnops.c
View File

@ -1621,11 +1621,23 @@ vn_suspendable(struct mount *mp)
* suspension is over, and then proceed.
*/
static int
vn_start_write_locked(struct mount *mp, int flags)
vn_start_write_refed(struct mount *mp, int flags, bool mplocked)
{
int error, mflags;
mtx_assert(MNT_MTX(mp), MA_OWNED);
if (__predict_true(!mplocked) && (flags & V_XSLEEP) == 0 &&
vfs_op_thread_enter(mp)) {
MPASS((mp->mnt_kern_flag & MNTK_SUSPEND) == 0);
atomic_add_int(&mp->mnt_writeopcount, 1);
vfs_op_thread_exit(mp);
return (0);
}
if (mplocked)
mtx_assert(MNT_MTX(mp), MA_OWNED);
else
MNT_ILOCK(mp);
error = 0;
/*
@ -1648,7 +1660,7 @@ vn_start_write_locked(struct mount *mp, int flags)
}
if (flags & V_XSLEEP)
goto unlock;
mp->mnt_writeopcount++;
atomic_add_int(&mp->mnt_writeopcount, 1);
unlock:
if (error != 0 || (flags & V_XSLEEP) != 0)
MNT_REL(mp);
@ -1694,11 +1706,10 @@ vn_start_write(struct vnode *vp, struct mount **mpp, int flags)
* refcount for the provided mountpoint too, in order to
* emulate a vfs_ref().
*/
MNT_ILOCK(mp);
if (vp == NULL && (flags & V_MNTREF) == 0)
MNT_REF(mp);
vfs_ref(mp);
return (vn_start_write_locked(mp, flags));
return (vn_start_write_refed(mp, flags, false));
}
/*
@ -1780,15 +1791,26 @@ vn_start_secondary_write(struct vnode *vp, struct mount **mpp, int flags)
void
vn_finished_write(struct mount *mp)
{
int c;
if (mp == NULL || !vn_suspendable(mp))
return;
if (vfs_op_thread_enter(mp)) {
c = atomic_fetchadd_int(&mp->mnt_writeopcount, -1) - 1;
if (c < 0)
panic("vn_finished_write: invalid writeopcount %d", c);
MNT_REL_UNLOCKED(mp);
vfs_op_thread_exit(mp);
return;
}
MNT_ILOCK(mp);
MNT_REL(mp);
mp->mnt_writeopcount--;
if (mp->mnt_writeopcount < 0)
panic("vn_finished_write: neg cnt");
if ((mp->mnt_kern_flag & MNTK_SUSPEND) != 0 &&
mp->mnt_writeopcount <= 0)
c = atomic_fetchadd_int(&mp->mnt_writeopcount, -1) - 1;
if (c < 0)
panic("vn_finished_write: invalid writeopcount %d", c);
if ((mp->mnt_kern_flag & MNTK_SUSPEND) != 0 && c == 0)
wakeup(&mp->mnt_writeopcount);
MNT_IUNLOCK(mp);
}
@ -1827,8 +1849,11 @@ vfs_write_suspend(struct mount *mp, int flags)
MPASS(vn_suspendable(mp));
vfs_op_enter(mp);
MNT_ILOCK(mp);
if (mp->mnt_susp_owner == curthread) {
vfs_op_exit_locked(mp);
MNT_IUNLOCK(mp);
return (EALREADY);
}
@ -1845,6 +1870,7 @@ vfs_write_suspend(struct mount *mp, int flags)
*/
if ((flags & VS_SKIP_UNMOUNT) != 0 &&
(mp->mnt_kern_flag & MNTK_UNMOUNT) != 0) {
vfs_op_exit_locked(mp);
MNT_IUNLOCK(mp);
return (EBUSY);
}
@ -1856,8 +1882,10 @@ vfs_write_suspend(struct mount *mp, int flags)
MNT_MTX(mp), (PUSER - 1)|PDROP, "suspwt", 0);
else
MNT_IUNLOCK(mp);
if ((error = VFS_SYNC(mp, MNT_SUSPEND)) != 0)
if ((error = VFS_SYNC(mp, MNT_SUSPEND)) != 0) {
vfs_write_resume(mp, 0);
vfs_op_exit(mp);
}
return (error);
}
@ -1881,14 +1909,15 @@ vfs_write_resume(struct mount *mp, int flags)
curthread->td_pflags &= ~TDP_IGNSUSP;
if ((flags & VR_START_WRITE) != 0) {
MNT_REF(mp);
mp->mnt_writeopcount++;
atomic_add_int(&mp->mnt_writeopcount, 1);
}
MNT_IUNLOCK(mp);
if ((flags & VR_NO_SUSPCLR) == 0)
VFS_SUSP_CLEAN(mp);
vfs_op_exit(mp);
} else if ((flags & VR_START_WRITE) != 0) {
MNT_REF(mp);
vn_start_write_locked(mp, 0);
vn_start_write_refed(mp, 0, true);
} else {
MNT_IUNLOCK(mp);
}

9
sys/ufs/ffs/ffs_softdep.c
View File

@ -2954,17 +2954,26 @@ journal_suspend(ump)
{
struct jblocks *jblocks;
struct mount *mp;
bool set;
mp = UFSTOVFS(ump);
if ((mp->mnt_kern_flag & MNTK_SUSPEND) != 0)
return;
jblocks = ump->softdep_jblocks;
vfs_op_enter(mp);
set = false;
MNT_ILOCK(mp);
if ((mp->mnt_kern_flag & MNTK_SUSPEND) == 0) {
stat_journal_min++;
mp->mnt_kern_flag |= MNTK_SUSPEND;
mp->mnt_susp_owner = ump->softdep_flushtd;
set = true;
}
jblocks->jb_suspended = 1;
MNT_IUNLOCK(mp);
if (!set)
vfs_op_exit(mp);
}
static int