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Take the vm object lock in read mode in vnode_generic_putpages().

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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
This commit is contained in:
Konstantin Belousov 2017-10-20 18:40:29 +00:00
parent 9e9a610115
commit b3d4ab6645
1 changed files with 13 additions and 5 deletions
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18
sys/vm/vnode_pager.c
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@ -1252,8 +1252,14 @@ vnode_pager_generic_putpages(struct vnode *vp, vm_page_t *ma, int bytecount,
* 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_t *ma, int bytecount,
}
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]);