Date: Fri, 29 Oct 2010 21:51:05 +0400 From: Artemiev Igor <ai@kliksys.ru> To: freebsd-stable@freebsd.org, freebsd-fs@freebsd.org Subject: Re: 8.1-STABLE: zfs and sendfile: problem still exists Message-ID: <20101029175105.GB18613@two.kliksys.ru> In-Reply-To: <4CCAF0EB.4080001@icyb.net.ua> References: <3D1C350B94A44E5D95BAA1596D1EBF13@vosz.local> <20101029090417.GA17537@two.kliksys.ru> <4CCABFC2.3040701@icyb.net.ua> <4CCADD37.7000306@icyb.net.ua> <20101029152602.GA18613@two.kliksys.ru> <4CCAF0EB.4080001@icyb.net.ua>
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On Fri, Oct 29, 2010 at 07:06:03PM +0300, Andriy Gapon wrote:
> Probably yes, but have to be careful there.
> First, do vm_page_grab only for UIO_NOCOPY case.
> Second, the first page is already "shared busy" after vm_page_io_start() call in
> kern_sendfile; so you might need VM_ALLOC_IGN_SBUSY for that page to avoid a deadlock.
RELENG_8 doesn`t have VM_ALLOC_IGN_SBUSY, it appeared only in HEAD.
Can you review this patch, Whether correctly I have understood? (didnt test it yet)
--- sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c.orig 2010-10-29 18:18:23.921078337 +0200
+++ sys/cddl/contrib/opensolaris/uts/common/fs/zfs/zfs_vnops.c 2010-10-29 19:23:48.142513084 +0200
@@ -449,7 +449,7 @@
int bytes = MIN(PAGESIZE - off, len);
again:
- if ((m = vm_page_lookup(obj, OFF_TO_IDX(start))) != NULL &&
+ if (uio->uio_segflg != UIO_NOCOPY && (m = vm_page_lookup(obj, OFF_TO_IDX(start))) != NULL &&
vm_page_is_valid(m, off, bytes)) {
if (vm_page_sleep_if_busy(m, FALSE, "zfsmrb"))
goto again;
@@ -464,7 +464,7 @@
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@
@@ -472,11 +472,9 @@
* but it pessimize performance of sendfile/UFS, that's
* why I handle this special case in ZFS code.
*/
- KASSERT(off == 0,
- ("unexpected offset in mappedread for sendfile"));
- if (vm_page_sleep_if_busy(m, FALSE, "zfsmrb"))
- goto again;
- vm_page_busy(m);
+ if((m = vm_page_lookup(obj, OFF_TO_IDX(start))) == NULL || !vm_page_is_valid(m, off, bytes))
+ m = vm_page_grab(obj, OFF_TO_IDX(start), VM_ALLOC_NORMAL|VM_ALLOC_RETRY);
+
VM_OBJECT_UNLOCK(obj);
if (dirbytes > 0) {
error = dmu_read_uio(os, zp->z_id, uio,
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