Date: Wed, 17 Jun 2015 17:28:50 +0300 From: Gleb Smirnoff <glebius@FreeBSD.org> To: Konstantin Belousov <kostikbel@gmail.com> Cc: Alan Cox <alc@rice.edu>, arch@FreeBSD.org Subject: Re: Step 2 Was: more strict KPI for vm_pager_get_pages() Message-ID: <20150617142850.GA73119@glebius.int.ru> In-Reply-To: <20150617134538.GY2080@kib.kiev.ua> References: <20150615212931.GG73119@glebius.int.ru> <20150617101444.GW73119@glebius.int.ru> <20150617134538.GY2080@kib.kiev.ua>
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Konstantin,
On Wed, Jun 17, 2015 at 04:45:38PM +0300, Konstantin Belousov wrote:
K> > +++ sys/vm/vm_pager.c (working copy)
K> > @@ -251,7 +251,88 @@ vm_pager_deallocate(object)
K> > }
K> >
K> > /*
K> > - * vm_pager_get_pages() - inline, see vm/vm_pager.h
K> > + * Retrieve pages from the VM system in order to map them into an object
K> > + * ( or into VM space somewhere ). If the pagein was successful, we
K> > + * must fully validate it.
K> > + */
K> > +int
K> > +vm_pager_get_pages(vm_object_t object, vm_page_t *m, int count, int reqpage)
K> > +{
K> > + int r;
K> > +
K> > + VM_OBJECT_ASSERT_WLOCKED(object);
K> > + KASSERT(count > 0, ("%s: 0 count", __func__));
K> > +
K> > +#ifdef INVARIANTS
K> > + /*
K> > + * All pages must be busied, not mapped, not valid (save the last one),
K> > + * not dirty and belong to the proper object.
K> > + */
K> > + for (int i = 0 ; i < count; i++) {
K> > + vm_page_assert_xbusied(m[i]);
K> > + KASSERT(!pmap_page_is_mapped(m[i]),
K> > + ("%s: page %p is mapped", __func__, m[i]));
K> > + KASSERT(m[i]->valid == 0 || i == count - 1,
K> > + ("%s: request for a valid page %p", __func__, m[i]));
K> Are you sure that e.g. the requested page cannot be partially valid ?
K> I am surprised.
All save the last one are always valid. This passed stress2 for me and pho@.
K> > + KASSERT(m[i]->dirty == 0,
K> > + ("%s: page %p is dirty", __func__, m[i]));
K> > + KASSERT(m[i]->object == object,
K> > + ("%s: wrong object %p/%p", __func__, object, m[i]->object));
K> > + }
K> > +#endif
K> Create a helper function with the loop, and use it, instead of copying
K> the block twice.
Done.
K> > +
K> > + r = (*pagertab[object->type]->pgo_getpages)(object, m, count, reqpage);
K> > + if (r != VM_PAGER_OK)
K> > + return (r);
K> > +
K> > + /*
K> > + * If pager has replaced the page, assert that it had
K> > + * updated the array.
K> > + */
K> > + KASSERT(m[reqpage] == vm_page_lookup(object, m[reqpage]->pindex),
K> > + ("%s: mismatch page %p pindex %ju", __func__,
K> > + m[reqpage], (uintmax_t )m[reqpage]->pindex - 1));
K> Why -1 ?
K> Need an empty line after assert, to deliniate the code which is commented
K> about.
That's an artifact from future patch. Fixed.
K> Also, you may assert that the requested page is still busied.
Done.
Updated patch attached.
--
Totus tuus, Glebius.
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Index: sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c
===================================================================
--- sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c (revision 284504)
+++ sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c (working copy)
@@ -5734,8 +5734,6 @@ zfs_getpages(struct vnode *vp, vm_page_t *m, int c
object = mreq->object;
error = 0;
- KASSERT(vp->v_object == object, ("mismatching object"));
-
if (pcount > 1 && zp->z_blksz > PAGESIZE) {
startoff = rounddown(IDX_TO_OFF(mreq->pindex), zp->z_blksz);
reqstart = OFF_TO_IDX(round_page(startoff));
Index: sys/fs/nfsclient/nfs_clbio.c
===================================================================
--- sys/fs/nfsclient/nfs_clbio.c (revision 284504)
+++ sys/fs/nfsclient/nfs_clbio.c (working copy)
@@ -129,12 +129,6 @@ ncl_getpages(struct vop_getpages_args *ap)
npages = btoc(count);
/*
- * Since the caller has busied the requested page, that page's valid
- * field will not be changed by other threads.
- */
- vm_page_assert_xbusied(pages[ap->a_reqpage]);
-
- /*
* If the requested page is partially valid, just return it and
* allow the pager to zero-out the blanks. Partially valid pages
* can only occur at the file EOF.
Index: sys/vm/swap_pager.c
===================================================================
--- sys/vm/swap_pager.c (revision 284504)
+++ sys/vm/swap_pager.c (working copy)
@@ -1118,10 +1118,6 @@ swap_pager_getpages(vm_object_t object, vm_page_t
mreq = m[reqpage];
- KASSERT(mreq->object == object,
- ("swap_pager_getpages: object mismatch %p/%p",
- object, mreq->object));
-
/*
* Calculate range to retrieve. The pages have already been assigned
* their swapblks. We require a *contiguous* range but we know it to
Index: sys/vm/vm_pager.c
===================================================================
--- sys/vm/vm_pager.c (revision 284504)
+++ sys/vm/vm_pager.c (working copy)
@@ -250,8 +250,79 @@ vm_pager_deallocate(object)
(*pagertab[object->type]->pgo_dealloc) (object);
}
+static void
+vm_pager_assert_in(vm_object_t object, vm_page_t *m, int count)
+{
+#ifdef INVARIANTS
+
+ VM_OBJECT_ASSERT_WLOCKED(object);
+ KASSERT(count > 0, ("%s: 0 count", __func__));
+ /*
+ * All pages must be busied, not mapped, not valid (save the last one),
+ * not dirty and belong to the proper object.
+ */
+ for (int i = 0 ; i < count; i++) {
+ vm_page_assert_xbusied(m[i]);
+ KASSERT(!pmap_page_is_mapped(m[i]),
+ ("%s: page %p is mapped", __func__, m[i]));
+ KASSERT(m[i]->valid == 0 || i == count - 1,
+ ("%s: request for a valid page %p", __func__, m[i]));
+ KASSERT(m[i]->dirty == 0,
+ ("%s: page %p is dirty", __func__, m[i]));
+ KASSERT(m[i]->object == object,
+ ("%s: wrong object %p/%p", __func__, object, m[i]->object));
+ }
+#endif
+}
+
/*
- * vm_pager_get_pages() - inline, see vm/vm_pager.h
+ * Retrieve pages from the VM system in order to map them into an object
+ * ( or into VM space somewhere ). If the pagein was successful, we
+ * must fully validate it.
+ */
+int
+vm_pager_get_pages(vm_object_t object, vm_page_t *m, int count, int reqpage)
+{
+ int r;
+
+ vm_pager_assert_in(object, m, count);
+
+ r = (*pagertab[object->type]->pgo_getpages)(object, m, count, reqpage);
+ if (r != VM_PAGER_OK)
+ return (r);
+
+ /*
+ * If pager has replaced the page, assert that it had
+ * updated the array. Also assert that page is still
+ * busied.
+ */
+ KASSERT(m[reqpage] == vm_page_lookup(object, m[reqpage]->pindex),
+ ("%s: mismatch page %p pindex %ju", __func__,
+ m[reqpage], (uintmax_t )m[reqpage]->pindex));
+ vm_page_assert_xbusied(m[reqpage]);
+
+ /*
+ * Pager didn't fill up entire page. Zero out
+ * partially filled data.
+ */
+ if (m[reqpage]->valid != VM_PAGE_BITS_ALL)
+ vm_page_zero_invalid(m[reqpage], TRUE);
+
+ return (VM_PAGER_OK);
+}
+
+int
+vm_pager_get_pages_async(vm_object_t object, vm_page_t *m, int count,
+ int reqpage, pgo_getpages_iodone_t iodone, void *arg)
+{
+
+ vm_pager_assert_in(object, m, count);
+
+ return ((*pagertab[object->type]->pgo_getpages_async)(object, m,
+ count, reqpage, iodone, arg));
+}
+
+/*
* vm_pager_put_pages() - inline, see vm/vm_pager.h
* vm_pager_has_page() - inline, see vm/vm_pager.h
*/
Index: sys/vm/vm_pager.h
===================================================================
--- sys/vm/vm_pager.h (revision 284504)
+++ sys/vm/vm_pager.h (working copy)
@@ -106,9 +106,9 @@ vm_object_t vm_pager_allocate(objtype_t, void *, v
vm_ooffset_t, struct ucred *);
void vm_pager_bufferinit(void);
void vm_pager_deallocate(vm_object_t);
-static __inline int vm_pager_get_pages(vm_object_t, vm_page_t *, int, int);
-static inline int vm_pager_get_pages_async(vm_object_t, vm_page_t *, int,
- int, pgo_getpages_iodone_t, void *);
+int vm_pager_get_pages(vm_object_t, vm_page_t *, int, int);
+int vm_pager_get_pages_async(vm_object_t, vm_page_t *, int, int,
+ pgo_getpages_iodone_t, void *);
static __inline boolean_t vm_pager_has_page(vm_object_t, vm_pindex_t, int *, int *);
void vm_pager_init(void);
vm_object_t vm_pager_object_lookup(struct pagerlst *, void *);
@@ -115,40 +115,6 @@ vm_object_t vm_pager_object_lookup(struct pagerlst
void vm_pager_free_nonreq(vm_object_t object, vm_page_t ma[], int reqpage,
int npages, boolean_t object_locked);
-/*
- * vm_page_get_pages:
- *
- * Retrieve pages from the VM system in order to map them into an object
- * ( or into VM space somewhere ). If the pagein was successful, we
- * must fully validate it.
- */
-static __inline int
-vm_pager_get_pages(
- vm_object_t object,
- vm_page_t *m,
- int count,
- int reqpage
-) {
- int r;
-
- VM_OBJECT_ASSERT_WLOCKED(object);
- r = (*pagertab[object->type]->pgo_getpages)(object, m, count, reqpage);
- if (r == VM_PAGER_OK && m[reqpage]->valid != VM_PAGE_BITS_ALL) {
- vm_page_zero_invalid(m[reqpage], TRUE);
- }
- return (r);
-}
-
-static inline int
-vm_pager_get_pages_async(vm_object_t object, vm_page_t *m, int count,
- int reqpage, pgo_getpages_iodone_t iodone, void *arg)
-{
-
- VM_OBJECT_ASSERT_WLOCKED(object);
- return ((*pagertab[object->type]->pgo_getpages_async)(object, m,
- count, reqpage, iodone, arg));
-}
-
static __inline void
vm_pager_put_pages(
vm_object_t object,
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