PR/55658 CVS commit: src/sys/uvm

["Rin Okuyama" <rin%netbsd.org@localhost>]

The following reply was made to PR kern/55658; it has been noted by GNATS.

From: "Rin Okuyama" <rin%netbsd.org@localhost>
To: gnats-bugs%gnats.NetBSD.org@localhost
Cc: 
Subject: PR/55658 CVS commit: src/sys/uvm
Date: Sun, 18 Oct 2020 08:52:15 +0000

 Module Name:	src
 Committed By:	rin
 Date:		Sun Oct 18 08:52:15 UTC 2020
 
 Modified Files:
 	src/sys/uvm: uvm_bio.c
 
 Log Message:
 PR kern/55658
 
 Revert rev 1.122:
 http://cvsweb.netbsd.org/bsdweb.cgi/src/sys/uvm/uvm_bio.c#rev1.122
 
 If this commit is applied to NFS client, changes to files in client
 side are sometimes invisible in server side, which results in file
 corruption.
 
 Demonstrated by test code provided by Anthony Mallet:
 https://mail-index.netbsd.org/current-users/2020/10/17/msg039708.html
 
 Whether the test case above passes or not depends on architectures
 and size of NFS I/O specified by -r and -w options of mount_nfs(8)
 (the default size is 32KB for x86 and 8KB for other archs).
 
 Whereas it fails on amd64 and i386 with the default size, it passes
 on other archs (aarch64, arm, alpha, m68k, and powerpc at least) with
 their default. On most ports, it fails with some I/O sizes.
 
 However, the condition for failure is still unclear; whereas it fails
 with 2KB I/O size on amiga (m68k, 8KB page), it passes with same I/O
 size on alpha (8KB page). It may depends on some VM parameters or
 details in pmap implementation, or some race conditions are involved.
 
 Great thanks to Anthony Mallet for providing the test code, and sorry
 everyone for breakage.
 
 
 To generate a diff of this commit:
 cvs rdiff -u -r1.122 -r1.123 src/sys/uvm/uvm_bio.c
 
 Please note that diffs are not public domain; they are subject to the
 copyright notices on the relevant files.