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vfs: make write suspension mandatory

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At the time opt-in was introduced adding yourself as a writer was esrializing
across the mount point. Nowadays it is fully per-cpu, the only impact being
a small single-threaded hit on top of what's there right now.

Vast majority of the overhead stems from the call to VOP_GETWRITEMOUNT which
has is done regardless.

Should someone want to microoptimize this single-threaded they can coalesce
looking the mount up with adding a write to it.
This commit is contained in:
Mateusz Guzik 2020-02-15 13:00:39 +00:00
parent ec0234b4c2
commit 074ad60a4c
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=357962
2 changed files with 2 additions and 36 deletions
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10
sys/fs/tmpfs/tmpfs_vfsops.c
View File

@ -88,7 +88,6 @@ static int tmpfs_root(struct mount *, int flags, struct vnode **);
static int tmpfs_fhtovp(struct mount *, struct fid *, int,
struct vnode **);
static int tmpfs_statfs(struct mount *, struct statfs *);
static void tmpfs_susp_clean(struct mount *);
static const char *tmpfs_opts[] = {
"from", "size", "maxfilesize", "inodes", "uid", "gid", "mode", "export",
@ -646,14 +645,6 @@ tmpfs_sync(struct mount *mp, int waitfor)
return (0);
}
/*
* The presence of a susp_clean method tells the VFS to track writes.
*/
static void
tmpfs_susp_clean(struct mount *mp __unused)
{
}
static int
tmpfs_init(struct vfsconf *conf)
{
@ -679,7 +670,6 @@ struct vfsops tmpfs_vfsops = {
.vfs_statfs = tmpfs_statfs,
.vfs_fhtovp = tmpfs_fhtovp,
.vfs_sync = tmpfs_sync,
.vfs_susp_clean = tmpfs_susp_clean,
.vfs_init = tmpfs_init,
.vfs_uninit = tmpfs_uninit,
};

28
sys/kern/vfs_vnops.c
View File

@ -1643,13 +1643,6 @@ vn_closefile(struct file *fp, struct thread *td)
return (error);
}
static bool
vn_suspendable(struct mount *mp)
{
return (mp->mnt_op->vfs_susp_clean != NULL);
}
/*
* Preparing to start a filesystem write operation. If the operation is
* permitted, then we bump the count of operations in progress and
@ -1729,12 +1722,6 @@ vn_start_write(struct vnode *vp, struct mount **mpp, int flags)
if ((mp = *mpp) == NULL)
return (0);
if (!vn_suspendable(mp)) {
if (vp != NULL || (flags & V_MNTREF) != 0)
vfs_rel(mp);
return (0);
}
/*
* VOP_GETWRITEMOUNT() returns with the mp refcount held through
* a vfs_ref().
@ -1780,12 +1767,6 @@ vn_start_secondary_write(struct vnode *vp, struct mount **mpp, int flags)
if ((mp = *mpp) == NULL)
return (0);
if (!vn_suspendable(mp)) {
if (vp != NULL || (flags & V_MNTREF) != 0)
vfs_rel(mp);
return (0);
}
/*
* VOP_GETWRITEMOUNT() returns with the mp refcount held through
* a vfs_ref().
@ -1829,7 +1810,7 @@ vn_finished_write(struct mount *mp)
{
int c;
if (mp == NULL || !vn_suspendable(mp))
if (mp == NULL)
return;
if (vfs_op_thread_enter(mp)) {
@ -1863,7 +1844,7 @@ vn_finished_write(struct mount *mp)
void
vn_finished_secondary_write(struct mount *mp)
{
if (mp == NULL || !vn_suspendable(mp))
if (mp == NULL)
return;
MNT_ILOCK(mp);
MNT_REL(mp);
@ -1884,8 +1865,6 @@ vfs_write_suspend(struct mount *mp, int flags)
{
int error;
MPASS(vn_suspendable(mp));
vfs_op_enter(mp);
MNT_ILOCK(mp);
@ -1934,8 +1913,6 @@ void
vfs_write_resume(struct mount *mp, int flags)
{
MPASS(vn_suspendable(mp));
MNT_ILOCK(mp);
if ((mp->mnt_kern_flag & MNTK_SUSPEND) != 0) {
KASSERT(mp->mnt_susp_owner == curthread, ("mnt_susp_owner"));
@ -1970,7 +1947,6 @@ vfs_write_suspend_umnt(struct mount *mp)
{
int error;
MPASS(vn_suspendable(mp));
KASSERT((curthread->td_pflags & TDP_IGNSUSP) == 0,
("vfs_write_suspend_umnt: recursed"));