Since commit a49bd4d71637 ("mm, numa: rework do_pages_move"), the
semantic of move_pages() has changed to return the number of
non-migrated pages if they were result of a non-fatal reasons
(usually a busy page). This was an unintentional change that
hasn't been noticed except for LTP tests which checked for the
documented behavior.
There are two ways to go around this change. We can even get back
to the original behavior and return -EAGAIN whenever migrate_pages
is not able to migrate pages due to non-fatal reasons. Another
option would be to simply continue with the changed semantic and
extend move_pages documentation to clarify that -errno is returned
on an invalid input or when migration simply cannot succeed (e.g.
-ENOMEM, -EBUSY) or the number of pages that couldn't have been
migrated due to ephemeral reasons (e.g. page is pinned or locked
for other reasons).
We decided to keep the second option in kernel because this
behavior is in place for some time without anybody complaining and
possibly new users depending on it. Also it allows to have a
slightly easier error handling as the caller knows that it is
worth to retry when err > 0.
Update man pages to reflect the new semantic.
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Yang Shi <yang.shi@linux.alibaba.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Document that the signum argument is ignored in newer kernels, but
that user space should pass a valid real-time signal number for
backwards compatibility.
Cowritten-by: Eugene Syromyatnikov <evgsyr@gmail.com>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Eugene Syromyatnikov <evgsyr@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Verified from inspection of kernel source code.
Reported-by: Manfred Spraul <manfred@colorfullife.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
The paragraph on Linux VM is rather generic, and does not belong
in DESCRIPTION. In fact, I'm not sure it even belongs in this
page. At the least, let's move it to NOTES.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
And while we are at it, remove a sentence that makes an obvious
point (that mremap() uses the Linux page table scheme).
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Details of glibc 2.4, which is by now fairly old, would be
better at the end of NOTES than at the start.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
From a mailing list conversation:
On 5/24/18 9:03 PM, Heinrich Schuchardt wrote:
> Hello Michael,
>
> in the mmap(2) man page MAP_ANON is described as deprecated.
>
> When I look at the NetBSD manpage
> http://netbsd.gw.com/cgi-bin/man-cgi?mmap+2+NetBSD-current
> I found that MAP_ANONYMOUS is not defined.
>
> https://www.dragonflybsd.org/cgi/web-man?command=mmap§ion=2
> indicates MAP_ANONYMOUS is an alias for MAP_ANON and is provided for
> compatibility.
>
> https://man.openbsd.org/mmap.2 also knows MAP_ANONYMOUS as a synonym.
>
> https://www.unix.com/man-page/osx/2/mmap/ does not know MAP_ANONYMOUS.
>
> So shouldn't the man page indicate that MAP_ANON is to be favored to
> write portable code? And correspondingly mark MAP_ANONYMOUS as synonym
> only kept for compatibility.
>
> The Open Group Base Specifications Issue 7, 2018 Edition does not
> reference either of both. So both values are not POSIX but it is not
> correct to describe them as Linux only.
The text saying that MAP_ANON is deprecated is ancient (at least
20 years old). I don't know why that text was added.
Things are not simple though: it looks like there's at least
one historical implementation (HP-US) that defines MAP_ANONYMOUS
but not MAP_ANON.
I've applied the patch below.
Reported-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
As noted by Heinrich Schuchardt:
he list contains hex values of different constants. I just wonder for
which architecture (alpha, i386, mips, or sparc at that time). No
information is supplied.
Current values depend on the architecture, e.g.
On amd64
0x82307201 VFAT_IOCTL_READDIR_BOTH
0x82307202 VFAT_IOCTL_READDIR_SHORT
0x80047210 FAT_IOCTL_GET_ATTRIBUTES
0x40047211 FAT_IOCTL_SET_ATTRIBUTES
0x80047213 FAT_IOCTL_GET_VOLUME_ID
On mips
0x42187201 VFAT_IOCTL_READDIR_BOTH
0x42187202 VFAT_IOCTL_READDIR_SHORT
0x40047210 FAT_IOCTL_GET_ATTRIBUTES
0x80047211 FAT_IOCTL_SET_ATTRIBUTES
0x40047213 FAT_IOCTL_GET_VOLUME_ID
Hence hex values should be removed.
Reported-by:
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Linux kernel commit 337684a1746f "fs: return EPERM on immutable
inode" changed (nd unified the return value of the utimensat(2)
from -EACCES to -EPERM in case of an immutable flag. Modify the
man page to reflect the same.
The entire discussion of returning the correct return value is at:
http://lists.linux.it/pipermail/ltp/2017-January/003424.html
[mtk: The change was in Linux 4.8]
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
A year cannot only begin with week number 53 of the previous year but
also with week number 52. Year 2011 is an example for this case, as
can be easily seen with GNU date:
$ date -d "jan 1 2011" "+%c %V %G"
Sat Jan 1 00:00:00 2011 52 2010
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
The sysctls fs.protected_fifos and fs.protected_regular can cause
open(2) to fail with EACCES (see Documentation/sysctl/fs.rst for
details.)
Signed-off-by: Joseph C. Sible <josephcsible@gmail.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
As far as I can see, /proc/sys/fs/aio-max-nr is a
system-wide limit, not a per-user limit. This seems to be
confirmed by comments in fs/aio.c (Linux 5.6) sources).
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
The restriction to CAP_SYS_ADMIN was removed from map_files in
2015 [1]. There was a fixme that indicted this might happen, but
the main text was never updated when this commit landed. While
we're at it, add a note about the ptrace access check that is
still required.
[1] bdb4d100af
Signed-off-by: Keno Fischer <keno@juliacomputing.com>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
The info here is mostly ancient, certainly incomplete,
and is not consistently maintained. Best to remove it, I think.
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
Yang Shi