Author: kib
Date: Thu Mar 15 11:06:37 2012
New Revision: 233001
URL: http://svn.freebsd.org/changeset/base/233001
Log:
MFC r232071:
Account the writeable shared mappings backed by file in the vnode
v_writecount.
MFC r232103:
Place the if() at the right location.
MFC note: the added struct vm_object un_pager.vnp.writemappings member
is located after the fields of struct vm_object that could be accessed
from the modules.
Modified:
stable/9/sys/vm/vm_map.c
stable/9/sys/vm/vm_map.h
stable/9/sys/vm/vm_mmap.c
stable/9/sys/vm/vm_object.h
stable/9/sys/vm/vnode_pager.c
stable/9/sys/vm/vnode_pager.h
Directory Properties:
stable/9/sys/ (props changed)
Modified: stable/9/sys/vm/vm_map.c
==============================================================================
--- stable/9/sys/vm/vm_map.c Thu Mar 15 08:39:10 2012 (r233000)
+++ stable/9/sys/vm/vm_map.c Thu Mar 15 11:06:37 2012 (r233001)
@@ -91,6 +91,7 @@ __FBSDID("$FreeBSD$");
#include <vm/vm_pager.h>
#include <vm/vm_kern.h>
#include <vm/vm_extern.h>
+#include <vm/vnode_pager.h>
#include <vm/swap_pager.h>
#include <vm/uma.h>
@@ -475,11 +476,23 @@ vm_map_process_deferred(void)
{
struct thread *td;
vm_map_entry_t entry;
+ vm_object_t object;
td = curthread;
-
while ((entry = td->td_map_def_user) != NULL) {
td->td_map_def_user = entry->next;
+ if ((entry->eflags & MAP_ENTRY_VN_WRITECNT) != 0) {
+ /*
+ * Decrement the object's writemappings and
+ * possibly the vnode's v_writecount.
+ */
+ KASSERT((entry->eflags & MAP_ENTRY_IS_SUB_MAP) == 0,
+ ("Submap with writecount"));
+ object = entry->object.vm_object;
+ KASSERT(object != NULL, ("No object for writecount"));
+ vnode_pager_release_writecount(object, entry->start,
+ entry->end);
+ }
vm_map_entry_deallocate(entry, FALSE);
}
}
@@ -1174,6 +1187,8 @@ vm_map_insert(vm_map_t map, vm_object_t
protoeflags |= MAP_ENTRY_NOSYNC;
if (cow & MAP_DISABLE_COREDUMP)
protoeflags |= MAP_ENTRY_NOCOREDUMP;
+ if (cow & MAP_VN_WRITECOUNT)
+ protoeflags |= MAP_ENTRY_VN_WRITECNT;
if (cow & MAP_INHERIT_SHARE)
inheritance = VM_INHERIT_SHARE;
else
@@ -1516,6 +1531,11 @@ vm_map_simplify_entry(vm_map_t map, vm_m
* references. Thus, the map lock can be kept
* without causing a lock-order reversal with
* the vnode lock.
+ *
+ * Since we count the number of virtual page
+ * mappings in object->un_pager.vnp.writemappings,
+ * the writemappings value should not be adjusted
+ * when the entry is disposed of.
*/
if (prev->object.vm_object)
vm_object_deallocate(prev->object.vm_object);
@@ -1627,6 +1647,13 @@ _vm_map_clip_start(vm_map_t map, vm_map_
if ((entry->eflags & MAP_ENTRY_IS_SUB_MAP) == 0) {
vm_object_reference(new_entry->object.vm_object);
+ /*
+ * The object->un_pager.vnp.writemappings for the
+ * object of MAP_ENTRY_VN_WRITECNT type entry shall be
+ * kept as is here. The virtual pages are
+ * re-distributed among the clipped entries, so the sum is
+ * left the same.
+ */
}
}
@@ -2900,6 +2927,7 @@ vm_map_copy_entry(
vm_ooffset_t *fork_charge)
{
vm_object_t src_object;
+ vm_map_entry_t fake_entry;
vm_offset_t size;
struct ucred *cred;
int charged;
@@ -2965,6 +2993,27 @@ vm_map_copy_entry(
src_entry->eflags |=
(MAP_ENTRY_COW|MAP_ENTRY_NEEDS_COPY);
dst_entry->eflags |=
(MAP_ENTRY_COW|MAP_ENTRY_NEEDS_COPY);
dst_entry->offset = src_entry->offset;
+ if (src_entry->eflags & MAP_ENTRY_VN_WRITECNT) {
+ /*
+ * MAP_ENTRY_VN_WRITECNT cannot
+ * indicate write reference from
+ * src_entry, since the entry is
+ * marked as needs copy. Allocate a
+ * fake entry that is used to
+ * decrement object->un_pager.vnp.writecount
+ * at the appropriate time. Attach
+ * fake_entry to the deferred list.
+ */
+ fake_entry = vm_map_entry_create(dst_map);
+ fake_entry->eflags = MAP_ENTRY_VN_WRITECNT;
+ src_entry->eflags &= ~MAP_ENTRY_VN_WRITECNT;
+ vm_object_reference(src_object);
+ fake_entry->object.vm_object = src_object;
+ fake_entry->start = src_entry->start;
+ fake_entry->end = src_entry->end;
+ fake_entry->next = curthread->td_map_def_user;
+ curthread->td_map_def_user = fake_entry;
+ }
} else {
dst_entry->object.vm_object = NULL;
dst_entry->offset = 0;
@@ -3043,6 +3092,7 @@ vmspace_fork(struct vmspace *vm1, vm_oof
vm_map_lock(old_map);
if (old_map->busy)
vm_map_wait_busy(old_map);
+ new_map = NULL; /* silence gcc */
vm2 = vmspace_alloc(old_map->min_offset, old_map->max_offset);
if (vm2 == NULL)
goto unlock_and_return;
@@ -3122,6 +3172,16 @@ vmspace_fork(struct vmspace *vm1, vm_oof
new_entry->eflags &= ~(MAP_ENTRY_USER_WIRED |
MAP_ENTRY_IN_TRANSITION);
new_entry->wired_count = 0;
+ if (new_entry->eflags & MAP_ENTRY_VN_WRITECNT) {
+ object = new_entry->object.vm_object;
+ KASSERT(((struct vnode *)object->handle)->
+ v_writecount > 0,
+ ("vmspace_fork: v_writecount"));
+ KASSERT(object->un_pager.vnp.writemappings > 0,
+ ("vmspace_fork: vnp.writecount"));
+ vnode_pager_update_writecount(object,
+ new_entry->start, new_entry->end);
+ }
/*
* Insert the entry into the new map -- we know we're
@@ -3146,8 +3206,11 @@ vmspace_fork(struct vmspace *vm1, vm_oof
*/
new_entry = vm_map_entry_create(new_map);
*new_entry = *old_entry;
+ /*
+ * Copied entry is COW over the old object.
+ */
new_entry->eflags &= ~(MAP_ENTRY_USER_WIRED |
- MAP_ENTRY_IN_TRANSITION);
+ MAP_ENTRY_IN_TRANSITION | MAP_ENTRY_VN_WRITECNT);
new_entry->wired_count = 0;
new_entry->object.vm_object = NULL;
new_entry->cred = NULL;
@@ -3161,9 +3224,15 @@ vmspace_fork(struct vmspace *vm1, vm_oof
old_entry = old_entry->next;
}
unlock_and_return:
- vm_map_unlock(old_map);
+ /*
+ * Use inlined vm_map_unlock() to postpone handling the deferred
+ * map entries, which cannot be done until both old_map and
+ * new_map locks are released.
+ */
+ sx_xunlock(&old_map->lock);
if (vm2 != NULL)
- vm_map_unlock(new_map);
+ sx_xunlock(&new_map->lock);
+ vm_map_process_deferred();
return (vm2);
}
Modified: stable/9/sys/vm/vm_map.h
==============================================================================
--- stable/9/sys/vm/vm_map.h Thu Mar 15 08:39:10 2012 (r233000)
+++ stable/9/sys/vm/vm_map.h Thu Mar 15 11:06:37 2012 (r233001)
@@ -139,6 +139,7 @@ struct vm_map_entry {
#define MAP_ENTRY_GROWS_UP 0x2000 /* Bottom-up stacks */
#define MAP_ENTRY_WIRE_SKIPPED 0x4000
+#define MAP_ENTRY_VN_WRITECNT 0x8000 /* writeable vnode
mapping */
#ifdef _KERNEL
static __inline u_char
@@ -315,6 +316,7 @@ long vmspace_wired_count(struct vmspace
#define MAP_DISABLE_SYNCER 0x0020
#define MAP_DISABLE_COREDUMP 0x0100
#define MAP_PREFAULT_MADVISE 0x0200 /* from (user) madvise request */
+#define MAP_VN_WRITECOUNT 0x0400
#define MAP_STACK_GROWS_DOWN 0x1000
#define MAP_STACK_GROWS_UP 0x2000
#define MAP_ACC_CHARGED 0x4000
Modified: stable/9/sys/vm/vm_mmap.c
==============================================================================
--- stable/9/sys/vm/vm_mmap.c Thu Mar 15 08:39:10 2012 (r233000)
+++ stable/9/sys/vm/vm_mmap.c Thu Mar 15 11:06:37 2012 (r233001)
@@ -81,6 +81,7 @@ __FBSDID("$FreeBSD$");
#include <vm/vm_pageout.h>
#include <vm/vm_extern.h>
#include <vm/vm_page.h>
+#include <vm/vnode_pager.h>
#ifdef HWPMC_HOOKS
#include <sys/pmckern.h>
@@ -93,7 +94,7 @@ struct sbrk_args {
#endif
static int vm_mmap_vnode(struct thread *, vm_size_t, vm_prot_t, vm_prot_t *,
- int *, struct vnode *, vm_ooffset_t *, vm_object_t *);
+ int *, struct vnode *, vm_ooffset_t *, vm_object_t *, boolean_t *);
static int vm_mmap_cdev(struct thread *, vm_size_t, vm_prot_t, vm_prot_t *,
int *, struct cdev *, vm_ooffset_t *, vm_object_t *);
static int vm_mmap_shm(struct thread *, vm_size_t, vm_prot_t, vm_prot_t *,
@@ -1218,28 +1219,33 @@ sys_munlock(td, uap)
/*
* vm_mmap_vnode()
*
- * MPSAFE
- *
* Helper function for vm_mmap. Perform sanity check specific for mmap
* operations on vnodes.
+ *
+ * For VCHR vnodes, the vnode lock is held over the call to
+ * vm_mmap_cdev() to keep vp->v_rdev valid.
*/
int
vm_mmap_vnode(struct thread *td, vm_size_t objsize,
vm_prot_t prot, vm_prot_t *maxprotp, int *flagsp,
- struct vnode *vp, vm_ooffset_t *foffp, vm_object_t *objp)
+ struct vnode *vp, vm_ooffset_t *foffp, vm_object_t *objp,
+ boolean_t *writecounted)
{
struct vattr va;
vm_object_t obj;
vm_offset_t foff;
struct mount *mp;
struct ucred *cred;
- int error, flags;
- int vfslocked;
+ int error, flags, locktype, vfslocked;
mp = vp->v_mount;
cred = td->td_ucred;
+ if ((*maxprotp & VM_PROT_WRITE) && (*flagsp & MAP_SHARED))
+ locktype = LK_EXCLUSIVE;
+ else
+ locktype = LK_SHARED;
vfslocked = VFS_LOCK_GIANT(mp);
- if ((error = vget(vp, LK_SHARED, td)) != 0) {
+ if ((error = vget(vp, locktype, td)) != 0) {
VFS_UNLOCK_GIANT(vfslocked);
return (error);
}
@@ -1256,8 +1262,20 @@ vm_mmap_vnode(struct thread *td, vm_size
}
if (obj->handle != vp) {
vput(vp);
- vp = (struct vnode*)obj->handle;
- vget(vp, LK_SHARED, td);
+ vp = (struct vnode *)obj->handle;
+ /*
+ * Bypass filesystems obey the mpsafety of the
+ * underlying fs.
+ */
+ error = vget(vp, locktype, td);
+ if (error != 0) {
+ VFS_UNLOCK_GIANT(vfslocked);
+ return (error);
+ }
+ }
+ if (locktype == LK_EXCLUSIVE) {
+ *writecounted = TRUE;
+ vnode_pager_update_writecount(obj, 0, objsize);
}
} else if (vp->v_type == VCHR) {
error = vm_mmap_cdev(td, objsize, prot, maxprotp, flagsp,
@@ -1293,7 +1311,7 @@ vm_mmap_vnode(struct thread *td, vm_size
objsize = round_page(va.va_size);
if (va.va_nlink == 0)
flags |= MAP_NOSYNC;
- obj = vm_pager_allocate(OBJT_VNODE, vp, objsize, prot, foff,
td->td_ucred);
+ obj = vm_pager_allocate(OBJT_VNODE, vp, objsize, prot, foff, cred);
if (obj == NULL) {
error = ENOMEM;
goto done;
@@ -1432,6 +1450,7 @@ vm_mmap(vm_map_t map, vm_offset_t *addr,
int rv = KERN_SUCCESS;
int docow, error;
struct thread *td = curthread;
+ boolean_t writecounted;
if (size == 0)
return (0);
@@ -1470,6 +1489,8 @@ vm_mmap(vm_map_t map, vm_offset_t *addr,
return (EINVAL);
fitit = FALSE;
}
+ writecounted = FALSE;
+
/*
* Lookup/allocate object.
*/
@@ -1480,7 +1501,7 @@ vm_mmap(vm_map_t map, vm_offset_t *addr,
break;
case OBJT_VNODE:
error = vm_mmap_vnode(td, size, prot, &maxprot, &flags,
- handle, &foff, &object);
+ handle, &foff, &object, &writecounted);
break;
case OBJT_SWAP:
error = vm_mmap_shm(td, size, prot, &maxprot, &flags,
@@ -1520,6 +1541,8 @@ vm_mmap(vm_map_t map, vm_offset_t *addr,
/* Shared memory is also shared with children. */
if (flags & MAP_SHARED)
docow |= MAP_INHERIT_SHARE;
+ if (writecounted)
+ docow |= MAP_VN_WRITECOUNT;
if (flags & MAP_STACK)
rv = vm_map_stack(map, *addr, size, prot, maxprot,
@@ -1537,7 +1560,12 @@ vm_mmap(vm_map_t map, vm_offset_t *addr,
* Lose the object reference. Will destroy the
* object if it's an unnamed anonymous mapping
* or named anonymous without other references.
+ *
+ * If this mapping was accounted for in the vnode's
+ * writecount, then undo that now.
*/
+ if (writecounted)
+ vnode_pager_release_writecount(object, 0, size);
vm_object_deallocate(object);
}
Modified: stable/9/sys/vm/vm_object.h
==============================================================================
--- stable/9/sys/vm/vm_object.h Thu Mar 15 08:39:10 2012 (r233000)
+++ stable/9/sys/vm/vm_object.h Thu Mar 15 11:06:37 2012 (r233001)
@@ -112,6 +112,7 @@ struct vm_object {
*/
struct {
off_t vnp_size;
+ vm_ooffset_t writemappings;
} vnp;
/*
Modified: stable/9/sys/vm/vnode_pager.c
==============================================================================
--- stable/9/sys/vm/vnode_pager.c Thu Mar 15 08:39:10 2012
(r233000)
+++ stable/9/sys/vm/vnode_pager.c Thu Mar 15 11:06:37 2012
(r233001)
@@ -222,6 +222,7 @@ retry:
object = vm_object_allocate(OBJT_VNODE,
OFF_TO_IDX(round_page(size)));
object->un_pager.vnp.vnp_size = size;
+ object->un_pager.vnp.writemappings = 0;
object->handle = handle;
VI_LOCK(vp);
@@ -268,10 +269,16 @@ vnode_pager_dealloc(object)
wakeup(object);
}
ASSERT_VOP_ELOCKED(vp, "vnode_pager_dealloc");
+ if (object->un_pager.vnp.writemappings > 0) {
+ object->un_pager.vnp.writemappings = 0;
+ vp->v_writecount--;
+ }
vp->v_object = NULL;
vp->v_vflag &= ~VV_TEXT;
+ VM_OBJECT_UNLOCK(object);
while (refs-- > 0)
vunref(vp);
+ VM_OBJECT_LOCK(object);
}
static boolean_t
@@ -1215,3 +1222,81 @@ vnode_pager_undirty_pages(vm_page_t *ma,
}
VM_OBJECT_UNLOCK(obj);
}
+
+void
+vnode_pager_update_writecount(vm_object_t object, vm_offset_t start,
+ vm_offset_t end)
+{
+ struct vnode *vp;
+ vm_ooffset_t old_wm;
+
+ VM_OBJECT_LOCK(object);
+ if (object->type != OBJT_VNODE) {
+ VM_OBJECT_UNLOCK(object);
+ return;
+ }
+ old_wm = object->un_pager.vnp.writemappings;
+ object->un_pager.vnp.writemappings += (vm_ooffset_t)end - start;
+ vp = object->handle;
+ if (old_wm == 0 && object->un_pager.vnp.writemappings != 0) {
+ ASSERT_VOP_ELOCKED(vp, "v_writecount inc");
+ vp->v_writecount++;
+ } else if (old_wm != 0 && object->un_pager.vnp.writemappings == 0) {
+ ASSERT_VOP_ELOCKED(vp, "v_writecount dec");
+ vp->v_writecount--;
+ }
+ VM_OBJECT_UNLOCK(object);
+}
+
+void
+vnode_pager_release_writecount(vm_object_t object, vm_offset_t start,
+ vm_offset_t end)
+{
+ struct vnode *vp;
+ struct mount *mp;
+ vm_offset_t inc;
+ int vfslocked;
+
+ VM_OBJECT_LOCK(object);
+
+ /*
+ * First, recheck the object type to account for the race when
+ * the vnode is reclaimed.
+ */
+ if (object->type != OBJT_VNODE) {
+ VM_OBJECT_UNLOCK(object);
+ return;
+ }
+
+ /*
+ * Optimize for the case when writemappings is not going to
+ * zero.
+ */
+ inc = end - start;
+ if (object->un_pager.vnp.writemappings != inc) {
+ object->un_pager.vnp.writemappings -= inc;
+ VM_OBJECT_UNLOCK(object);
+ return;
+ }
+
+ vp = object->handle;
+ vhold(vp);
+ VM_OBJECT_UNLOCK(object);
+ vfslocked = VFS_LOCK_GIANT(vp->v_mount);
+ mp = NULL;
+ vn_start_write(vp, &mp, V_WAIT);
+ vn_lock(vp, LK_EXCLUSIVE | LK_RETRY);
+
+ /*
+ * Decrement the object's writemappings, by swapping the start
+ * and end arguments for vnode_pager_update_writecount(). If
+ * there was not a race with vnode reclaimation, then the
+ * vnode's v_writecount is decremented.
+ */
+ vnode_pager_update_writecount(object, end, start);
+ VOP_UNLOCK(vp, 0);
+ vdrop(vp);
+ if (mp != NULL)
+ vn_finished_write(mp);
+ VFS_UNLOCK_GIANT(vfslocked);
+}
Modified: stable/9/sys/vm/vnode_pager.h
==============================================================================
--- stable/9/sys/vm/vnode_pager.h Thu Mar 15 08:39:10 2012
(r233000)
+++ stable/9/sys/vm/vnode_pager.h Thu Mar 15 11:06:37 2012
(r233001)
@@ -46,7 +46,11 @@ int vnode_pager_generic_putpages(struct
int count, boolean_t sync,
int *rtvals);
+void vnode_pager_release_writecount(vm_object_t object, vm_offset_t start,
+ vm_offset_t end);
void vnode_pager_undirty_pages(vm_page_t *ma, int *rtvals, int written);
+void vnode_pager_update_writecount(vm_object_t object, vm_offset_t start,
+ vm_offset_t end);
#endif /* _KERNEL */
#endif /* _VNODE_PAGER_ */
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