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Linux: Define Clear/Set PageError macros as NOPs

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The Linux 6.12 commit 'mm: remove PG_error' (09022bc196d23) removed
the PG_error page flag and the associated ClearPageError() and
SetPageError() functions (via removing the PAGEFLAG(Error, ...) macro).
The PG_error flag has not been used by core VFS/MM Linux code for some
time, possibly ever, and so our calls to these functions do not have any
practical effect, since we also do not check for the PG_error flag.
While we could simply remove these calls, play it safe and keep them
around until ClearPageError()/SetPageError() are removed.

The specific semantics of the PG_error flag are not completely well
defined in the Linux kernel, which appears to be one of the motivations
for its removal. Some Linux commits that mention some details on how the
flag is not useful for read errors include:

  7edf1ec5b249 ceph: don't SetPageError on readpage errors
  41a638a1b3fc affs: convert affs_symlink_read_folio() to use the folio
  2b2553f12355 btrfs: stop setting PageError in the data I/O path

Add a configure test to see if ClearPageError()/SetPageError() are
available in the Linux kernel; if they are not, define
ClearPageError()/SetPageError() as no-ops.

Change-Id: I2d3235d81030aa0b30907336f58a7d9c5c7b8026
Reviewed-on: https://gerrit.openafs.org/15876
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Tested-by: Cheyenne Wills <cwills@sinenomine.net>
Reviewed-by: Michael Meffie <mmeffie@sinenomine.net>
Reviewed-by: Mark Vitale <mvitale@sinenomine.net>
Reviewed-by: Marcio Brito Barbosa <mbarbosa@sinenomine.net>
Reviewed-by: Andrew Deason <adeason@sinenomine.net>
This commit is contained in:
Cheyenne Wills 2024-11-08 21:32:46 -07:00 committed by Andrew Deason
parent 4f82b5bd49
commit ec14690531
3 changed files with 33 additions and 0 deletions
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13
src/afs/LINUX/osi_compat.h
View File

@ -31,6 +31,19 @@
# endif
#endif
#if defined(HAVE_LINUX_NO_SETPAGEERROR)
static inline void
ClearPageError(struct page *p)
{
return;
}
static inline void
SetPageError(struct page *p)
{
return;
}
#endif
#if !defined(HAVE_LINUX_KTHREAD_COMPLETE_AND_EXIT)
# define kthread_complete_and_exit complete_and_exit
#endif

4
src/afs/LINUX/osi_pagecopy.c
View File

@ -56,12 +56,16 @@
#include <afsconfig.h>
#include "afs/param.h"
#include "afs/sysincludes.h"
#include "afsincludes.h"
#include <linux/pagemap.h>
#include <linux/kthread.h>
#include <linux/wait.h>
#include <linux/workqueue.h>
#include <linux/slab.h>
#include "osi_pagecopy.h"
#include "osi_compat.h"
static DECLARE_WAIT_QUEUE_HEAD (afs_pagecopy_wq);
static spinlock_t afs_pagecopy_lock;

16
src/cf/linux-kernel-func.m4
View File

@ -291,6 +291,22 @@ AC_CHECK_LINUX_FUNC([no_generic_file_splice_read],
[[static char buff[10], *ap;
ap = generic_file_splice_read(buff); ]])
dnl Linux 6.12 removed the PG_error flag from the page flags along with the
dnl associated functions ClearPageError() and SetPageError(). Check to see if
dnl these functions are present in the kernel.
dnl
dnl To check if ClearPageError() and SetPageError() are missing, define our own
dnl functions with the same name but with a conflicting signature. If we can
dnl define them, the real functions must be missing.
AC_CHECK_LINUX_FUNC([no_setpageerror],
[[#include <asm/page.h>
#include <linux/page-flags.h>
static inline char ClearPageError(char c) { return c;}
static inline char SetPageError(char c) { return c;}]],
[[static char r;
r = ClearPageError('x');
r = SetPageError('x');]])
dnl Consequences - things which get set as a result of the
dnl above tests
AS_IF([test "x$ac_cv_linux_func_d_alloc_anon" = "xno"],