Re: uvm_fault: entering swap code

2020-12-13 Thread Jonathan Matthew 
On Sat, Dec 12, 2020 at 10:54:57PM +1000, Jonathan Matthew wrote:
> On Thu, Dec 10, 2020 at 10:46:58AM -0300, Martin Pieuchot wrote:
> > On 08/12/20(Tue) 22:55, Jonathan Matthew wrote:
> > > On Mon, Dec 07, 2020 at 03:15:50PM -0300, Martin Pieuchot wrote:
> > > > Getting a page from the fault handler might require poking at some
> > > > swap-related states.
> > > > 
> > > > These are not in the hot-path of the fault handler so for the moment
> > > > just assert that the KERNEL_LOCK() is held or grab it if the function
> > > > might be called from an future unlocked path.
> > > > 
> > > > ok?
> > > 
> > > Could you add 'K' to the list of locks in the comment above struct uvmexp 
> > > too?
> > 
> > Updated diff below.
> > 
> > > I went looking for other uses of swpgonly and saw that it's used under
> > > uvm_map_teardown -> uvm_unmap_kill_entry -> uvm_km_pgremove,
> > > and uvm_map_teardown ensures that the kernel lock is not held.
> > > Not related to this diff exactly, but is this something we need to fix?
> > 
> > I suppose that the problem can only occur if a kernel thread is exiting
> > since this code is only executed for the kernel pmap.  Anyway I added an
> > assertion.
> 
> Right, and as I understand it, kernel threads all share the proc0 vm space,
> so its reference count won't ever reach 0, so the kernel map portions of
> uvm_unmap_kill_entry() can't be reached from the reaper.  Looks like this is
> all safe, it just requires a bit more reading than I did the first time.
> I'll see if I can find a way to make it more clear.

And now that I've tested this out and checked that it doesn't blow up when
you drive the machine into swap, ok jmatthew@

> 
> > 
> > Index: uvm/uvm_km.c
> > ===
> > RCS file: /cvs/src/sys/uvm/uvm_km.c,v
> > retrieving revision 1.137
> > diff -u -p -r1.137 uvm_km.c
> > --- uvm/uvm_km.c23 May 2020 06:15:09 -  1.137
> > +++ uvm/uvm_km.c10 Dec 2020 13:33:49 -
> > @@ -243,6 +243,7 @@ uvm_km_pgremove(struct uvm_object *uobj,
> > voff_t curoff;
> > int slot;
> >  
> > +   KERNEL_ASSERT_LOCKED();
> > KASSERT(uobj->pgops == _pager);
> >  
> > for (curoff = start ; curoff < end ; curoff += PAGE_SIZE) {
> > Index: uvm/uvm_swap.c
> > ===
> > RCS file: /cvs/src/sys/uvm/uvm_swap.c,v
> > retrieving revision 1.147
> > diff -u -p -r1.147 uvm_swap.c
> > --- uvm/uvm_swap.c  29 Sep 2020 11:47:41 -  1.147
> > +++ uvm/uvm_swap.c  10 Dec 2020 13:30:30 -
> > @@ -1403,7 +1403,7 @@ uvm_swap_alloc(int *nslots, boolean_t le
> > /*
> >  * lock data lock, convert slots into blocks, and enter loop
> >  */
> > -
> > +   KERNEL_ASSERT_LOCKED();
> >  ReTry: /* XXXMRG */
> > LIST_FOREACH(spp, _priority, spi_swappri) {
> > TAILQ_FOREACH(sdp, >spi_swapdev, swd_next) {
> > @@ -1449,8 +1449,10 @@ uvm_swapisfull(void)
> >  {
> > int result;
> >  
> > +   KERNEL_LOCK();
> > KASSERT(uvmexp.swpgonly <= uvmexp.swpages);
> > result = (uvmexp.swpgonly == uvmexp.swpages);
> > +   KERNEL_UNLOCK();
> >  
> > return result;
> >  }
> > @@ -1465,6 +1467,7 @@ uvm_swap_markbad(int startslot, int nslo
> >  {
> > struct swapdev *sdp;
> >  
> > +   KERNEL_LOCK();
> > sdp = swapdrum_getsdp(startslot);
> > if (sdp != NULL) {
> > /*
> > @@ -1475,6 +1478,7 @@ uvm_swap_markbad(int startslot, int nslo
> >  */
> > sdp->swd_npgbad += nslots;
> > }
> > +   KERNEL_UNLOCK();
> >  }
> >  
> >  /*
> > @@ -1501,7 +1505,7 @@ uvm_swap_free(int startslot, int nslots)
> >  * in the extent, and return.   must hold pri lock to do
> >  * lookup and access the extent.
> >  */
> > -
> > +   KERNEL_LOCK();
> > sdp = swapdrum_getsdp(startslot);
> > KASSERT(uvmexp.nswapdev >= 1);
> > KASSERT(sdp != NULL);
> > @@ -1533,6 +1537,7 @@ uvm_swap_free(int startslot, int nslots)
> > }
> > }
> >  #endif /* UVM_SWAP_ENCRYPT */
> > +   KERNEL_UNLOCK();
> >  }
> >  
> >  /*
> > @@ -1567,6 +1572,7 @@ uvm_swap_get(struct vm_page *page, int s
> > return VM_PAGER_ERROR;
> > }
> >  
> > +   KERNEL_LOCK();
> > /* this page is (about to be) no longer only in swap. */
> > uvmexp.swpgonly--;
> >  
> > @@ -1577,7 +1583,7 @@ uvm_swap_get(struct vm_page *page, int s
> > /* oops, the read failed so it really is still only in swap. */
> > uvmexp.swpgonly++;
> > }
> > -
> > +   KERNEL_UNLOCK();
> > return (result);
> >  }
> >  
> > @@ -1599,6 +1605,8 @@ uvm_swap_io(struct vm_page **pps, int st
> > struct swapdev *sdp;
> > int encrypt = 0;
> >  #endif
> > +
> > +   KERNEL_ASSERT_LOCKED();
> >  
> > write = (flags & B_READ) == 0;
> > async = (flags & B_ASYNC) != 0;
> > Index: uvm/uvmexp.h
> > ===
> > RCS file:

Re: uvm_fault: entering swap code

2020-12-12 Thread Jonathan Matthew 
On Thu, Dec 10, 2020 at 10:46:58AM -0300, Martin Pieuchot wrote:
> On 08/12/20(Tue) 22:55, Jonathan Matthew wrote:
> > On Mon, Dec 07, 2020 at 03:15:50PM -0300, Martin Pieuchot wrote:
> > > Getting a page from the fault handler might require poking at some
> > > swap-related states.
> > > 
> > > These are not in the hot-path of the fault handler so for the moment
> > > just assert that the KERNEL_LOCK() is held or grab it if the function
> > > might be called from an future unlocked path.
> > > 
> > > ok?
> > 
> > Could you add 'K' to the list of locks in the comment above struct uvmexp 
> > too?
> 
> Updated diff below.
> 
> > I went looking for other uses of swpgonly and saw that it's used under
> > uvm_map_teardown -> uvm_unmap_kill_entry -> uvm_km_pgremove,
> > and uvm_map_teardown ensures that the kernel lock is not held.
> > Not related to this diff exactly, but is this something we need to fix?
> 
> I suppose that the problem can only occur if a kernel thread is exiting
> since this code is only executed for the kernel pmap.  Anyway I added an
> assertion.

Right, and as I understand it, kernel threads all share the proc0 vm space,
so its reference count won't ever reach 0, so the kernel map portions of
uvm_unmap_kill_entry() can't be reached from the reaper.  Looks like this is
all safe, it just requires a bit more reading than I did the first time.
I'll see if I can find a way to make it more clear.

> 
> Index: uvm/uvm_km.c
> ===
> RCS file: /cvs/src/sys/uvm/uvm_km.c,v
> retrieving revision 1.137
> diff -u -p -r1.137 uvm_km.c
> --- uvm/uvm_km.c  23 May 2020 06:15:09 -  1.137
> +++ uvm/uvm_km.c  10 Dec 2020 13:33:49 -
> @@ -243,6 +243,7 @@ uvm_km_pgremove(struct uvm_object *uobj,
>   voff_t curoff;
>   int slot;
>  
> + KERNEL_ASSERT_LOCKED();
>   KASSERT(uobj->pgops == _pager);
>  
>   for (curoff = start ; curoff < end ; curoff += PAGE_SIZE) {
> Index: uvm/uvm_swap.c
> ===
> RCS file: /cvs/src/sys/uvm/uvm_swap.c,v
> retrieving revision 1.147
> diff -u -p -r1.147 uvm_swap.c
> --- uvm/uvm_swap.c29 Sep 2020 11:47:41 -  1.147
> +++ uvm/uvm_swap.c10 Dec 2020 13:30:30 -
> @@ -1403,7 +1403,7 @@ uvm_swap_alloc(int *nslots, boolean_t le
>   /*
>* lock data lock, convert slots into blocks, and enter loop
>*/
> -
> + KERNEL_ASSERT_LOCKED();
>  ReTry:   /* XXXMRG */
>   LIST_FOREACH(spp, _priority, spi_swappri) {
>   TAILQ_FOREACH(sdp, >spi_swapdev, swd_next) {
> @@ -1449,8 +1449,10 @@ uvm_swapisfull(void)
>  {
>   int result;
>  
> + KERNEL_LOCK();
>   KASSERT(uvmexp.swpgonly <= uvmexp.swpages);
>   result = (uvmexp.swpgonly == uvmexp.swpages);
> + KERNEL_UNLOCK();
>  
>   return result;
>  }
> @@ -1465,6 +1467,7 @@ uvm_swap_markbad(int startslot, int nslo
>  {
>   struct swapdev *sdp;
>  
> + KERNEL_LOCK();
>   sdp = swapdrum_getsdp(startslot);
>   if (sdp != NULL) {
>   /*
> @@ -1475,6 +1478,7 @@ uvm_swap_markbad(int startslot, int nslo
>*/
>   sdp->swd_npgbad += nslots;
>   }
> + KERNEL_UNLOCK();
>  }
>  
>  /*
> @@ -1501,7 +1505,7 @@ uvm_swap_free(int startslot, int nslots)
>* in the extent, and return.   must hold pri lock to do
>* lookup and access the extent.
>*/
> -
> + KERNEL_LOCK();
>   sdp = swapdrum_getsdp(startslot);
>   KASSERT(uvmexp.nswapdev >= 1);
>   KASSERT(sdp != NULL);
> @@ -1533,6 +1537,7 @@ uvm_swap_free(int startslot, int nslots)
>   }
>   }
>  #endif /* UVM_SWAP_ENCRYPT */
> + KERNEL_UNLOCK();
>  }
>  
>  /*
> @@ -1567,6 +1572,7 @@ uvm_swap_get(struct vm_page *page, int s
>   return VM_PAGER_ERROR;
>   }
>  
> + KERNEL_LOCK();
>   /* this page is (about to be) no longer only in swap. */
>   uvmexp.swpgonly--;
>  
> @@ -1577,7 +1583,7 @@ uvm_swap_get(struct vm_page *page, int s
>   /* oops, the read failed so it really is still only in swap. */
>   uvmexp.swpgonly++;
>   }
> -
> + KERNEL_UNLOCK();
>   return (result);
>  }
>  
> @@ -1599,6 +1605,8 @@ uvm_swap_io(struct vm_page **pps, int st
>   struct swapdev *sdp;
>   int encrypt = 0;
>  #endif
> +
> + KERNEL_ASSERT_LOCKED();
>  
>   write = (flags & B_READ) == 0;
>   async = (flags & B_ASYNC) != 0;
> Index: uvm/uvmexp.h
> ===
> RCS file: /cvs/src/sys/uvm/uvmexp.h,v
> retrieving revision 1.6
> diff -u -p -r1.6 uvmexp.h
> --- uvm/uvmexp.h  1 Dec 2020 13:56:22 -   1.6
> +++ uvm/uvmexp.h  10 Dec 2020 13:31:01 -
> @@ -42,6 +42,7 @@
>   *
>   *  Locks used to protect struct members in this file:
>   *   I   immutable after creation
> + *   K   kernel lock
>   *   F   uvm_lock_fpageq

Re: uvm_fault: entering swap code

2020-12-10 Thread Martin Pieuchot 
On 08/12/20(Tue) 22:55, Jonathan Matthew wrote:
> On Mon, Dec 07, 2020 at 03:15:50PM -0300, Martin Pieuchot wrote:
> > Getting a page from the fault handler might require poking at some
> > swap-related states.
> > 
> > These are not in the hot-path of the fault handler so for the moment
> > just assert that the KERNEL_LOCK() is held or grab it if the function
> > might be called from an future unlocked path.
> > 
> > ok?
> 
> Could you add 'K' to the list of locks in the comment above struct uvmexp too?

Updated diff below.

> I went looking for other uses of swpgonly and saw that it's used under
> uvm_map_teardown -> uvm_unmap_kill_entry -> uvm_km_pgremove,
> and uvm_map_teardown ensures that the kernel lock is not held.
> Not related to this diff exactly, but is this something we need to fix?

I suppose that the problem can only occur if a kernel thread is exiting
since this code is only executed for the kernel pmap.  Anyway I added an
assertion.

Index: uvm/uvm_km.c
===
RCS file: /cvs/src/sys/uvm/uvm_km.c,v
retrieving revision 1.137
diff -u -p -r1.137 uvm_km.c
--- uvm/uvm_km.c23 May 2020 06:15:09 -  1.137
+++ uvm/uvm_km.c10 Dec 2020 13:33:49 -
@@ -243,6 +243,7 @@ uvm_km_pgremove(struct uvm_object *uobj,
voff_t curoff;
int slot;
 
+   KERNEL_ASSERT_LOCKED();
KASSERT(uobj->pgops == _pager);
 
for (curoff = start ; curoff < end ; curoff += PAGE_SIZE) {
Index: uvm/uvm_swap.c
===
RCS file: /cvs/src/sys/uvm/uvm_swap.c,v
retrieving revision 1.147
diff -u -p -r1.147 uvm_swap.c
--- uvm/uvm_swap.c  29 Sep 2020 11:47:41 -  1.147
+++ uvm/uvm_swap.c  10 Dec 2020 13:30:30 -
@@ -1403,7 +1403,7 @@ uvm_swap_alloc(int *nslots, boolean_t le
/*
 * lock data lock, convert slots into blocks, and enter loop
 */
-
+   KERNEL_ASSERT_LOCKED();
 ReTry: /* XXXMRG */
LIST_FOREACH(spp, _priority, spi_swappri) {
TAILQ_FOREACH(sdp, >spi_swapdev, swd_next) {
@@ -1449,8 +1449,10 @@ uvm_swapisfull(void)
 {
int result;
 
+   KERNEL_LOCK();
KASSERT(uvmexp.swpgonly <= uvmexp.swpages);
result = (uvmexp.swpgonly == uvmexp.swpages);
+   KERNEL_UNLOCK();
 
return result;
 }
@@ -1465,6 +1467,7 @@ uvm_swap_markbad(int startslot, int nslo
 {
struct swapdev *sdp;
 
+   KERNEL_LOCK();
sdp = swapdrum_getsdp(startslot);
if (sdp != NULL) {
/*
@@ -1475,6 +1478,7 @@ uvm_swap_markbad(int startslot, int nslo
 */
sdp->swd_npgbad += nslots;
}
+   KERNEL_UNLOCK();
 }
 
 /*
@@ -1501,7 +1505,7 @@ uvm_swap_free(int startslot, int nslots)
 * in the extent, and return.   must hold pri lock to do
 * lookup and access the extent.
 */
-
+   KERNEL_LOCK();
sdp = swapdrum_getsdp(startslot);
KASSERT(uvmexp.nswapdev >= 1);
KASSERT(sdp != NULL);
@@ -1533,6 +1537,7 @@ uvm_swap_free(int startslot, int nslots)
}
}
 #endif /* UVM_SWAP_ENCRYPT */
+   KERNEL_UNLOCK();
 }
 
 /*
@@ -1567,6 +1572,7 @@ uvm_swap_get(struct vm_page *page, int s
return VM_PAGER_ERROR;
}
 
+   KERNEL_LOCK();
/* this page is (about to be) no longer only in swap. */
uvmexp.swpgonly--;
 
@@ -1577,7 +1583,7 @@ uvm_swap_get(struct vm_page *page, int s
/* oops, the read failed so it really is still only in swap. */
uvmexp.swpgonly++;
}
-
+   KERNEL_UNLOCK();
return (result);
 }
 
@@ -1599,6 +1605,8 @@ uvm_swap_io(struct vm_page **pps, int st
struct swapdev *sdp;
int encrypt = 0;
 #endif
+
+   KERNEL_ASSERT_LOCKED();
 
write = (flags & B_READ) == 0;
async = (flags & B_ASYNC) != 0;
Index: uvm/uvmexp.h
===
RCS file: /cvs/src/sys/uvm/uvmexp.h,v
retrieving revision 1.6
diff -u -p -r1.6 uvmexp.h
--- uvm/uvmexp.h1 Dec 2020 13:56:22 -   1.6
+++ uvm/uvmexp.h10 Dec 2020 13:31:01 -
@@ -42,6 +42,7 @@
  *
  *  Locks used to protect struct members in this file:
  * I   immutable after creation
+ * K   kernel lock
  * F   uvm_lock_fpageq
  */
 struct uvmexp {
@@ -79,9 +80,9 @@ struct uvmexp {
 
/* swap */
int nswapdev;   /* number of configured swap devices in system */
-   int swpages;/* number of PAGE_SIZE'ed swap pages */
+   int swpages;/* [K] number of PAGE_SIZE'ed swap pages */
int swpginuse;  /* number of swap pages in use */
-   int swpgonly;   /* number of swap pages in use, not also in RAM */
+   int swpgonly;   /* [K] number of swap pages in use, not also in RAM */
int nswget; /* number of swap pages moved from disk to RAM */
int

Re: uvm_fault: entering swap code

2020-12-08 Thread Martin Pieuchot 
On 08/12/20(Tue) 22:55, Jonathan Matthew wrote:
> On Mon, Dec 07, 2020 at 03:15:50PM -0300, Martin Pieuchot wrote:
> > Getting a page from the fault handler might require poking at some
> > swap-related states.
> > 
> > These are not in the hot-path of the fault handler so for the moment
> > just assert that the KERNEL_LOCK() is held or grab it if the function
> > might be called from an future unlocked path.
> > 
> > ok?
> 
> Could you add 'K' to the list of locks in the comment above struct uvmexp too?
> 
> I went looking for other uses of swpgonly and saw that it's used under
> uvm_map_teardown -> uvm_unmap_kill_entry -> uvm_km_pgremove,
> and uvm_map_teardown ensures that the kernel lock is not held.
> Not related to this diff exactly, but is this something we need to fix?

Good catch!

uvm_km_pgremove() is indeed not safe to be called w/o KERNEL_LOCK() but
`swpgonly' is the minor of the problems :o)

  - uvm_pagelookup() iterates over `uvm_objtree' which as previously
explained is sometimes protected by the "page queue lock" sometimes
the KERNEL_LOCK(), here none is taken.  Note that for the moment the
KERNEL_LOCK prevails. 

  - calling tsleep_nsec() after checking PG_BUSY without being executed
under a lock is racy as the flag could be removed and a wakeup event
lost between the two conditions.

  - uao_dropswap() is certainly not ready to be called w/o KERNEL_LOCK().

> > Index: uvm/uvm_swap.c
> > ===
> > RCS file: /cvs/src/sys/uvm/uvm_swap.c,v
> > retrieving revision 1.147
> > diff -u -p -r1.147 uvm_swap.c
> > --- uvm/uvm_swap.c  29 Sep 2020 11:47:41 -  1.147
> > +++ uvm/uvm_swap.c  7 Dec 2020 18:07:03 -
> > @@ -1403,7 +1403,7 @@ uvm_swap_alloc(int *nslots, boolean_t le
> > /*
> >  * lock data lock, convert slots into blocks, and enter loop
> >  */
> > -
> > +   KERNEL_ASSERT_LOCKED();
> >  ReTry: /* XXXMRG */
> > LIST_FOREACH(spp, _priority, spi_swappri) {
> > TAILQ_FOREACH(sdp, >spi_swapdev, swd_next) {
> > @@ -1449,8 +1449,10 @@ uvm_swapisfull(void)
> >  {
> > int result;
> >  
> > +   KERNEL_LOCK();
> > KASSERT(uvmexp.swpgonly <= uvmexp.swpages);
> > result = (uvmexp.swpgonly == uvmexp.swpages);
> > +   KERNEL_UNLOCK();
> >  
> > return result;
> >  }
> > @@ -1465,6 +1467,7 @@ uvm_swap_markbad(int startslot, int nslo
> >  {
> > struct swapdev *sdp;
> >  
> > +   KERNEL_LOCK();
> > sdp = swapdrum_getsdp(startslot);
> > if (sdp != NULL) {
> > /*
> > @@ -1475,6 +1478,7 @@ uvm_swap_markbad(int startslot, int nslo
> >  */
> > sdp->swd_npgbad += nslots;
> > }
> > +   KERNEL_UNLOCK();
> >  }
> >  
> >  /*
> > @@ -1501,7 +1505,7 @@ uvm_swap_free(int startslot, int nslots)
> >  * in the extent, and return.   must hold pri lock to do
> >  * lookup and access the extent.
> >  */
> > -
> > +   KERNEL_LOCK();
> > sdp = swapdrum_getsdp(startslot);
> > KASSERT(uvmexp.nswapdev >= 1);
> > KASSERT(sdp != NULL);
> > @@ -1533,6 +1537,7 @@ uvm_swap_free(int startslot, int nslots)
> > }
> > }
> >  #endif /* UVM_SWAP_ENCRYPT */
> > +   KERNEL_UNLOCK();
> >  }
> >  
> >  /*
> > @@ -1567,6 +1572,7 @@ uvm_swap_get(struct vm_page *page, int s
> > return VM_PAGER_ERROR;
> > }
> >  
> > +   KERNEL_LOCK();
> > /* this page is (about to be) no longer only in swap. */
> > uvmexp.swpgonly--;
> >  
> > @@ -1577,7 +1583,7 @@ uvm_swap_get(struct vm_page *page, int s
> > /* oops, the read failed so it really is still only in swap. */
> > uvmexp.swpgonly++;
> > }
> > -
> > +   KERNEL_UNLOCK();
> > return (result);
> >  }
> >  
> > @@ -1599,6 +1605,8 @@ uvm_swap_io(struct vm_page **pps, int st
> > struct swapdev *sdp;
> > int encrypt = 0;
> >  #endif
> > +
> > +   KERNEL_ASSERT_LOCKED();
> >  
> > write = (flags & B_READ) == 0;
> > async = (flags & B_ASYNC) != 0;
> > Index: uvm/uvmexp.h
> > ===
> > RCS file: /cvs/src/sys/uvm/uvmexp.h,v
> > retrieving revision 1.6
> > diff -u -p -r1.6 uvmexp.h
> > --- uvm/uvmexp.h1 Dec 2020 13:56:22 -   1.6
> > +++ uvm/uvmexp.h7 Dec 2020 18:09:06 -
> > @@ -79,9 +79,9 @@ struct uvmexp {
> >  
> > /* swap */
> > int nswapdev;   /* number of configured swap devices in system */
> > -   int swpages;/* number of PAGE_SIZE'ed swap pages */
> > +   int swpages;/* [K] number of PAGE_SIZE'ed swap pages */
> > int swpginuse;  /* number of swap pages in use */
> > -   int swpgonly;   /* number of swap pages in use, not also in RAM */
> > +   int swpgonly;   /* [K] number of swap pages in use, not also in RAM */
> > int nswget; /* number of swap pages moved from disk to RAM */
> > int nanon;  /* XXX number total of anon's in system */
> > int unused05;   /* formerly nanonneeded */
>

Re: uvm_fault: entering swap code

2020-12-08 Thread Jonathan Matthew 
On Mon, Dec 07, 2020 at 03:15:50PM -0300, Martin Pieuchot wrote:
> Getting a page from the fault handler might require poking at some
> swap-related states.
> 
> These are not in the hot-path of the fault handler so for the moment
> just assert that the KERNEL_LOCK() is held or grab it if the function
> might be called from an future unlocked path.
> 
> ok?

Could you add 'K' to the list of locks in the comment above struct uvmexp too?

I went looking for other uses of swpgonly and saw that it's used under
uvm_map_teardown -> uvm_unmap_kill_entry -> uvm_km_pgremove,
and uvm_map_teardown ensures that the kernel lock is not held.
Not related to this diff exactly, but is this something we need to fix?


> 
> Index: uvm/uvm_swap.c
> ===
> RCS file: /cvs/src/sys/uvm/uvm_swap.c,v
> retrieving revision 1.147
> diff -u -p -r1.147 uvm_swap.c
> --- uvm/uvm_swap.c29 Sep 2020 11:47:41 -  1.147
> +++ uvm/uvm_swap.c7 Dec 2020 18:07:03 -
> @@ -1403,7 +1403,7 @@ uvm_swap_alloc(int *nslots, boolean_t le
>   /*
>* lock data lock, convert slots into blocks, and enter loop
>*/
> -
> + KERNEL_ASSERT_LOCKED();
>  ReTry:   /* XXXMRG */
>   LIST_FOREACH(spp, _priority, spi_swappri) {
>   TAILQ_FOREACH(sdp, >spi_swapdev, swd_next) {
> @@ -1449,8 +1449,10 @@ uvm_swapisfull(void)
>  {
>   int result;
>  
> + KERNEL_LOCK();
>   KASSERT(uvmexp.swpgonly <= uvmexp.swpages);
>   result = (uvmexp.swpgonly == uvmexp.swpages);
> + KERNEL_UNLOCK();
>  
>   return result;
>  }
> @@ -1465,6 +1467,7 @@ uvm_swap_markbad(int startslot, int nslo
>  {
>   struct swapdev *sdp;
>  
> + KERNEL_LOCK();
>   sdp = swapdrum_getsdp(startslot);
>   if (sdp != NULL) {
>   /*
> @@ -1475,6 +1478,7 @@ uvm_swap_markbad(int startslot, int nslo
>*/
>   sdp->swd_npgbad += nslots;
>   }
> + KERNEL_UNLOCK();
>  }
>  
>  /*
> @@ -1501,7 +1505,7 @@ uvm_swap_free(int startslot, int nslots)
>* in the extent, and return.   must hold pri lock to do
>* lookup and access the extent.
>*/
> -
> + KERNEL_LOCK();
>   sdp = swapdrum_getsdp(startslot);
>   KASSERT(uvmexp.nswapdev >= 1);
>   KASSERT(sdp != NULL);
> @@ -1533,6 +1537,7 @@ uvm_swap_free(int startslot, int nslots)
>   }
>   }
>  #endif /* UVM_SWAP_ENCRYPT */
> + KERNEL_UNLOCK();
>  }
>  
>  /*
> @@ -1567,6 +1572,7 @@ uvm_swap_get(struct vm_page *page, int s
>   return VM_PAGER_ERROR;
>   }
>  
> + KERNEL_LOCK();
>   /* this page is (about to be) no longer only in swap. */
>   uvmexp.swpgonly--;
>  
> @@ -1577,7 +1583,7 @@ uvm_swap_get(struct vm_page *page, int s
>   /* oops, the read failed so it really is still only in swap. */
>   uvmexp.swpgonly++;
>   }
> -
> + KERNEL_UNLOCK();
>   return (result);
>  }
>  
> @@ -1599,6 +1605,8 @@ uvm_swap_io(struct vm_page **pps, int st
>   struct swapdev *sdp;
>   int encrypt = 0;
>  #endif
> +
> + KERNEL_ASSERT_LOCKED();
>  
>   write = (flags & B_READ) == 0;
>   async = (flags & B_ASYNC) != 0;
> Index: uvm/uvmexp.h
> ===
> RCS file: /cvs/src/sys/uvm/uvmexp.h,v
> retrieving revision 1.6
> diff -u -p -r1.6 uvmexp.h
> --- uvm/uvmexp.h  1 Dec 2020 13:56:22 -   1.6
> +++ uvm/uvmexp.h  7 Dec 2020 18:09:06 -
> @@ -79,9 +79,9 @@ struct uvmexp {
>  
>   /* swap */
>   int nswapdev;   /* number of configured swap devices in system */
> - int swpages;/* number of PAGE_SIZE'ed swap pages */
> + int swpages;/* [K] number of PAGE_SIZE'ed swap pages */
>   int swpginuse;  /* number of swap pages in use */
> - int swpgonly;   /* number of swap pages in use, not also in RAM */
> + int swpgonly;   /* [K] number of swap pages in use, not also in RAM */
>   int nswget; /* number of swap pages moved from disk to RAM */
>   int nanon;  /* XXX number total of anon's in system */
>   int unused05;   /* formerly nanonneeded */
>

uvm_fault: entering swap code

2020-12-07 Thread Martin Pieuchot 
Getting a page from the fault handler might require poking at some
swap-related states.

These are not in the hot-path of the fault handler so for the moment
just assert that the KERNEL_LOCK() is held or grab it if the function
might be called from an future unlocked path.

ok?

Index: uvm/uvm_swap.c
===
RCS file: /cvs/src/sys/uvm/uvm_swap.c,v
retrieving revision 1.147
diff -u -p -r1.147 uvm_swap.c
--- uvm/uvm_swap.c  29 Sep 2020 11:47:41 -  1.147
+++ uvm/uvm_swap.c  7 Dec 2020 18:07:03 -
@@ -1403,7 +1403,7 @@ uvm_swap_alloc(int *nslots, boolean_t le
/*
 * lock data lock, convert slots into blocks, and enter loop
 */
-
+   KERNEL_ASSERT_LOCKED();
 ReTry: /* XXXMRG */
LIST_FOREACH(spp, _priority, spi_swappri) {
TAILQ_FOREACH(sdp, >spi_swapdev, swd_next) {
@@ -1449,8 +1449,10 @@ uvm_swapisfull(void)
 {
int result;
 
+   KERNEL_LOCK();
KASSERT(uvmexp.swpgonly <= uvmexp.swpages);
result = (uvmexp.swpgonly == uvmexp.swpages);
+   KERNEL_UNLOCK();
 
return result;
 }
@@ -1465,6 +1467,7 @@ uvm_swap_markbad(int startslot, int nslo
 {
struct swapdev *sdp;
 
+   KERNEL_LOCK();
sdp = swapdrum_getsdp(startslot);
if (sdp != NULL) {
/*
@@ -1475,6 +1478,7 @@ uvm_swap_markbad(int startslot, int nslo
 */
sdp->swd_npgbad += nslots;
}
+   KERNEL_UNLOCK();
 }
 
 /*
@@ -1501,7 +1505,7 @@ uvm_swap_free(int startslot, int nslots)
 * in the extent, and return.   must hold pri lock to do
 * lookup and access the extent.
 */
-
+   KERNEL_LOCK();
sdp = swapdrum_getsdp(startslot);
KASSERT(uvmexp.nswapdev >= 1);
KASSERT(sdp != NULL);
@@ -1533,6 +1537,7 @@ uvm_swap_free(int startslot, int nslots)
}
}
 #endif /* UVM_SWAP_ENCRYPT */
+   KERNEL_UNLOCK();
 }
 
 /*
@@ -1567,6 +1572,7 @@ uvm_swap_get(struct vm_page *page, int s
return VM_PAGER_ERROR;
}
 
+   KERNEL_LOCK();
/* this page is (about to be) no longer only in swap. */
uvmexp.swpgonly--;
 
@@ -1577,7 +1583,7 @@ uvm_swap_get(struct vm_page *page, int s
/* oops, the read failed so it really is still only in swap. */
uvmexp.swpgonly++;
}
-
+   KERNEL_UNLOCK();
return (result);
 }
 
@@ -1599,6 +1605,8 @@ uvm_swap_io(struct vm_page **pps, int st
struct swapdev *sdp;
int encrypt = 0;
 #endif
+
+   KERNEL_ASSERT_LOCKED();
 
write = (flags & B_READ) == 0;
async = (flags & B_ASYNC) != 0;
Index: uvm/uvmexp.h
===
RCS file: /cvs/src/sys/uvm/uvmexp.h,v
retrieving revision 1.6
diff -u -p -r1.6 uvmexp.h
--- uvm/uvmexp.h1 Dec 2020 13:56:22 -   1.6
+++ uvm/uvmexp.h7 Dec 2020 18:09:06 -
@@ -79,9 +79,9 @@ struct uvmexp {
 
/* swap */
int nswapdev;   /* number of configured swap devices in system */
-   int swpages;/* number of PAGE_SIZE'ed swap pages */
+   int swpages;/* [K] number of PAGE_SIZE'ed swap pages */
int swpginuse;  /* number of swap pages in use */
-   int swpgonly;   /* number of swap pages in use, not also in RAM */
+   int swpgonly;   /* [K] number of swap pages in use, not also in RAM */
int nswget; /* number of swap pages moved from disk to RAM */
int nanon;  /* XXX number total of anon's in system */
int unused05;   /* formerly nanonneeded */