8.1-STABLE: zfs and sendfile: problem still exists

[Kostik Belousov]

On Sat, Oct 30, 2010 at 05:43:54PM +0300, Andriy Gapon wrote:
> on 30/10/2010 14:25 Artemiev Igor said the following:
> > On Sat, Oct 30, 2010 at 01:33:00PM +0300, Andriy Gapon wrote:
> >> on 30/10/2010 13:12 Artemiev Igor said the following:
> >>> On Sat, Oct 30, 2010 at 12:52:54PM +0300, Andriy Gapon wrote:
> >>>
> >>>> Heh, next try.
> >>>
> >>> Got a panic, "vm_page_unwire: invalid wire count: 0"
> >>
> >> Oh, thank you for testing - forgot another piece (VM_ALLOC_WIRE for vm_page_alloc):
> > 
> > Yep, it work. But VM_ALLOC_WIRE not exists in RELENG_8, therefore i slightly modified your patch:
> 
> I apologize for my haste, it should have been VM_ALLOC_WIRED.
> Here is a corrected patch:
> Index: sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c
> ===================================================================
> --- sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c	(revision 214318)
> +++ sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c	(working copy)
> @@ -67,6 +67,7 @@
>  #include <sys/sf_buf.h>
>  #include <sys/sched.h>
>  #include <sys/acl.h>
> +#include <vm/vm_pageout.h>
> 
>  /*
>   * Programming rules.
> @@ -464,7 +465,7 @@
>  				uiomove_fromphys(&m, off, bytes, uio);
>  			VM_OBJECT_LOCK(obj);
>  			vm_page_wakeup(m);
> -		} else if (m != NULL && uio->uio_segflg == UIO_NOCOPY) {
> +		} else if (uio->uio_segflg == UIO_NOCOPY) {
>  			/*
>  			 * The code below is here to make sendfile(2) work
>  			 * correctly with ZFS. As pointed out by ups@
> @@ -474,9 +475,23 @@
>  			 */
>  			KASSERT(off == 0,
>  			    ("unexpected offset in mappedread for sendfile"));
> -			if (vm_page_sleep_if_busy(m, FALSE, "zfsmrb"))
> +			if (m != NULL && vm_page_sleep_if_busy(m, FALSE, "zfsmrb"))
>  				goto again;
> -			vm_page_busy(m);
> +			if (m == NULL) {
> +				m = vm_page_alloc(obj, OFF_TO_IDX(start),
> +				    VM_ALLOC_NOBUSY | VM_ALLOC_WIRED | VM_ALLOC_NORMAL);
> +				if (m == NULL) {
> +					VM_OBJECT_UNLOCK(obj);
> +					VM_WAIT;
> +					VM_OBJECT_LOCK(obj);
> +					goto again;
> +				}
> +			} else {
> +				vm_page_lock_queues();
> +				vm_page_wire(m);
> +				vm_page_unlock_queues();
> +			}
> +			vm_page_io_start(m);
Why wiring the page if it is busied ?
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