Gack! Absolutely correct J?rgen. I have filed 6806627 to track this.
-Mark
J?rgen Keil wrote:
> It seems there is a bug introduced by the putback for
>
> author: Mark Maybee <Mark.Maybee at Sun.COM>
> date: Wed Jan 28 11:04:37 2009 -0700 (2 weeks ago)
> files: usr/src/uts/common/fs/zfs/arc.c
> usr/src/uts/common/fs/zfs/sys/zfs_znode.h
> usr/src/uts/common/fs/zfs/zfs_rlock.c usr/src/uts/common/fs/zfs/zfs_vnops.c
> usr/src/uts/common/fs/zfs/zfs_znode.c
> description:
> 6551866 deadlock between zfs_write(), zfs_freesp(), and zfs_putapage()
> 6504953 zfs_getpage() misunderstands VOP_GETPAGE() interface
> 6702206 ZFS read/writer lock contention throttles sendfile() benchmark
> 6780491 Zone on a ZFS filesystem has poor fork/exec performance
> 6747596 assertion failed: DVA_EQUAL(BP_IDENTITY(&zio->io_bp_orig),
> BP_IDENTITY(zio->io_bp)));
>
> zfs_vnops, zfs_putpage()
>
>
> 3695 /*
> 3696 * Align this request to the file block size in case we
> kluster.
> 3697 * XXX - this can result in pretty aggresive locking,
> which can
> 3698 * impact simultanious read/write access. One option
> might be
> 3699 * to break up long requests (len == 0) into
> block-by-block
> 3700 * operations to get narrower locking.
> 3701 */
> 3702 blksz = zp->z_blksz;
> 3703 if (ISP2(blksz))
> 3704 io_off = P2ALIGN_TYPED(off, blksz, u_offset_t);
> 3705 else
> 3706 io_off = 0;
> 3707 if (len > 0 && ISP2(blksz))
> 3708 io_len = P2ROUNDUP_TYPED(len + (io_off - off),
> blksz, size_t);
> 3709 else
> 3710 io_len = 0;
> 3711
> 3712 if (io_len == 0) {
> 3713 /*
> 3714 * Search the entire vp list for pages >=
> io_off.
> 3715 */
> 3716 rl = zfs_range_lock(zp, io_off, UINT64_MAX,
> RL_WRITER);
> 3717 error = pvn_vplist_dirty(vp, io_off,
> zfs_putapage, flags, cr);
> 3718 goto out;
> 3719 }
> 3720 rl = zfs_range_lock(zp, io_off, io_len, RL_WRITER);
>
>
> Line 3708:
> "len + (io_off - off)" looks wrong, this should be
> "len + (off - io_off)". The P2ALIGN_TYPED() macro at line 3704
> should round down "off", i.e. io_off <= off.
>
>
> Test case:
>
> /files2/media/osol-0906-106a-global-x86.iso is a file on a zfs filesystem
>
> # mount -F hsfs /files2/media/osol-0906-106a-global-x86.iso /mnt
> # time mkisofs -r -o /dev/null /mnt
> <<< very slow >>>
> 1.22u 5.05s 59:37.46 0.1%
>
> On snv_104 the same test completes in 21 seconds.
>
> It has become 180x slower...
>
>
> diff --git a/usr/src/uts/common/fs/zfs/zfs_vnops.c
> b/usr/src/uts/common/fs/zfs/zfs_vnops.c
> --- a/usr/src/uts/common/fs/zfs/zfs_vnops.c
> +++ b/usr/src/uts/common/fs/zfs/zfs_vnops.c
> @@ -3705,7 +3705,7 @@
> else
> io_off = 0;
> if (len > 0 && ISP2(blksz))
> - io_len = P2ROUNDUP_TYPED(len + (io_off - off), blksz, size_t);
> + io_len = P2ROUNDUP_TYPED(len + (off - io_off), blksz, size_t);
> else
> io_len = 0;
