From: James Bottomley <James.Bottomley@steeleye.com>
To: Linus Torvalds <torvalds@osdl.org>
Cc: Linux Kernel <linux-kernel@vger.kernel.org>
Subject: [PATCH] fix remap of shared read only mappings
Date: 04 Sep 2003 10:49:18 -0400 [thread overview]
Message-ID: <1062686960.1829.11.camel@mulgrave> (raw)
When mmap MAP_SHARED is done on a file, it gets marked with VM_MAYSHARE
and, if it's read/write, VM_SHARED. However, if it is remapped with
mremap(), the MAP_SHARED is only passed into the new mapping based on
VM_SHARED. This means that remapped read only MAP_SHARED mappings lose
VM_MAYSHARE. This is causing us a problem on parisc because we have to
align all shared mappings carefully to mitigate cache aliasing problems.
The fix is to key passing the MAP_SHARED flag back into the remapped are
off VM_MAYSHARE not VM_SHARED.
James
===== mremap.c 1.32 vs 1.33 =====
--- 1.32/mm/mremap.c Thu Aug 7 12:29:10 2003
+++ 1.33/mm/mremap.c Sun Aug 24 06:50:10 2003
@@ -420,7 +420,7 @@
if (flags & MREMAP_MAYMOVE) {
if (!(flags & MREMAP_FIXED)) {
unsigned long map_flags = 0;
- if (vma->vm_flags & VM_SHARED)
+ if (vma->vm_flags & VM_MAYSHARE)
map_flags |= MAP_SHARED;
new_addr = get_unmapped_area(vma->vm_file, 0, new_len,
next reply other threads:[~2003-09-04 14:49 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-09-04 14:49 James Bottomley [this message]
2003-09-04 21:48 ` [PATCH] fix remap of shared read only mappings Jamie Lokier
2003-09-04 22:33 ` James Bottomley
2003-09-04 22:56 ` Jamie Lokier
2003-09-04 23:23 ` James Bottomley
2003-09-04 23:40 ` Jamie Lokier
2003-09-05 0:49 ` Daniel Phillips
2003-09-05 0:49 ` Linus Torvalds
2003-09-05 1:07 ` Alan Cox
2003-09-05 1:31 ` Daniel Phillips
2003-09-05 4:35 ` Linus Torvalds
2003-09-05 0:52 ` James Bottomley
2003-09-05 1:21 ` Daniel Phillips
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=1062686960.1829.11.camel@mulgrave \
--to=james.bottomley@steeleye.com \
--cc=linux-kernel@vger.kernel.org \
--cc=torvalds@osdl.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox