Author: kib
Date: Fri Oct 20 18:40:29 2017
New Revision: 324807
URL: https://svnweb.freebsd.org/changeset/base/324807
Log:
Take the vm object lock in read mode in vnode_generic_putpages().
Only upgrade it to write mode if we need to clear dirty bits of the
partially valid page after EOF.
Suggested and reviewed by: alc
Sponsored by: The FreeBSD Foundation
MFC after: 3 weeks
Modified:
head/sys/vm/vnode_pager.c
Modified: head/sys/vm/vnode_pager.c
==============================================================================
--- head/sys/vm/vnode_pager.c Fri Oct 20 15:29:28 2017 (r324806)
+++ head/sys/vm/vnode_pager.c Fri Oct 20 18:40:29 2017 (r324807)
@@ -1252,8 +1252,14 @@ vnode_pager_generic_putpages(struct vnode *vp, vm_page
* We do not under any circumstances truncate the valid bits, as
* this will screw up bogus page replacement.
*/
- VM_OBJECT_WLOCK(object);
+ VM_OBJECT_RLOCK(object);
if (maxsize + poffset > object->un_pager.vnp.vnp_size) {
+ if (!VM_OBJECT_TRYUPGRADE(object)) {
+ VM_OBJECT_RUNLOCK(object);
+ VM_OBJECT_WLOCK(object);
+ if (maxsize + poffset <= object->un_pager.vnp.vnp_size)
+ goto downgrade;
+ }
if (object->un_pager.vnp.vnp_size > poffset) {
maxsize = object->un_pager.vnp.vnp_size - poffset;
ncount = btoc(maxsize);
@@ -1278,6 +1284,8 @@ vnode_pager_generic_putpages(struct vnode *vp, vm_page
}
for (i = ncount; i < count; i++)
rtvals[i] = VM_PAGER_BAD;
+downgrade:
+ VM_OBJECT_LOCK_DOWNGRADE(object);
}
auio.uio_iov = &aiov;
@@ -1324,7 +1332,7 @@ start_write:
*/
MPASS(prev_offset < next_offset);
- VM_OBJECT_WUNLOCK(object);
+ VM_OBJECT_RUNLOCK(object);
aiov.iov_base = NULL;
auio.uio_iovcnt = 1;
auio.uio_offset = prev_offset;
@@ -1340,7 +1348,7 @@ start_write:
"zero-length write at %ju resid %zd\n",
auio.uio_offset, auio.uio_resid);
}
- VM_OBJECT_WLOCK(object);
+ VM_OBJECT_RLOCK(object);
break;
}
@@ -1358,7 +1366,7 @@ start_write:
vn_printf(vp, "vnode_pager_putpages: residual I/O %zd "
"at %ju\n", auio.uio_resid,
(uintmax_t)ma[0]->pindex);
- VM_OBJECT_WLOCK(object);
+ VM_OBJECT_RLOCK(object);
if (error != 0 || auio.uio_resid != 0)
break;
}
@@ -1372,7 +1380,7 @@ write_done:
/* Unwritten pages in range, free bonus if the page is clean. */
for (; i < ncount; i++)
rtvals[i] = ma[i]->dirty == 0 ? VM_PAGER_OK : VM_PAGER_ERROR;
- VM_OBJECT_WUNLOCK(object);
+ VM_OBJECT_RUNLOCK(object);
VM_CNT_ADD(v_vnodepgsout, i);
VM_CNT_INC(v_vnodeout);
return (rtvals[0]);
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