<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux-toradex.git/include/linux/jiffies.h, branch v2.6.27.50</title>
<subtitle>Linux kernel for Apalis and Colibri modules</subtitle>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/'/>
<entry>
<title>remove div_long_long_rem</title>
<updated>2008-05-01T15:03:58+00:00</updated>
<author>
<name>Roman Zippel</name>
<email>zippel@linux-m68k.org</email>
</author>
<published>2008-05-01T11:34:31+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=f8bd2258e2d520dff28c855658bd24bdafb5102d'/>
<id>f8bd2258e2d520dff28c855658bd24bdafb5102d</id>
<content type='text'>
x86 is the only arch right now, which provides an optimized for
div_long_long_rem and it has the downside that one has to be very careful that
the divide doesn't overflow.

The API is a little akward, as the arguments for the unsigned divide are
signed.  The signed version also doesn't handle a negative divisor and
produces worse code on 64bit archs.

There is little incentive to keep this API alive, so this converts the few
users to the new API.

Signed-off-by: Roman Zippel &lt;zippel@linux-m68k.org&gt;
Cc: Ralf Baechle &lt;ralf@linux-mips.org&gt;
Cc: Ingo Molnar &lt;mingo@elte.hu&gt;
Cc: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Cc: john stultz &lt;johnstul@us.ibm.com&gt;
Cc: Christoph Lameter &lt;clameter@sgi.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
x86 is the only arch right now, which provides an optimized for
div_long_long_rem and it has the downside that one has to be very careful that
the divide doesn't overflow.

The API is a little akward, as the arguments for the unsigned divide are
signed.  The signed version also doesn't handle a negative divisor and
produces worse code on 64bit archs.

There is little incentive to keep this API alive, so this converts the few
users to the new API.

Signed-off-by: Roman Zippel &lt;zippel@linux-m68k.org&gt;
Cc: Ralf Baechle &lt;ralf@linux-mips.org&gt;
Cc: Ingo Molnar &lt;mingo@elte.hu&gt;
Cc: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Cc: john stultz &lt;johnstul@us.ibm.com&gt;
Cc: Christoph Lameter &lt;clameter@sgi.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/juhl/trivial</title>
<updated>2008-04-21T23:36:46+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2008-04-21T23:36:46+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=e9b62693ae0a1e13ccc97a6792d9a7770c8d1b5b'/>
<id>e9b62693ae0a1e13ccc97a6792d9a7770c8d1b5b</id>
<content type='text'>
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/juhl/trivial: (24 commits)
  DOC:  A couple corrections and clarifications in USB doc.
  Generate a slightly more informative error msg for bad HZ
  fix typo "is" -&gt; "if" in Makefile
  ext*: spelling fix prefered -&gt; preferred
  DOCUMENTATION:  Use newer DEFINE_SPINLOCK macro in docs.
  KEYS:  Fix the comment to match the file name in rxrpc-type.h.
  RAID: remove trailing space from printk line
  DMA engine: typo fixes
  Remove unused MAX_NODES_SHIFT
  MAINTAINERS: Clarify access to OCFS2 development mailing list.
  V4L: Storage class should be before const qualifier (sn9c102)
  V4L: Storage class should be before const qualifier
  sonypi: Storage class should be before const qualifier
  intel_menlow: Storage class should be before const qualifier
  DVB: Storage class should be before const qualifier
  arm: Storage class should be before const qualifier
  ALSA: Storage class should be before const qualifier
  acpi: Storage class should be before const qualifier
  firmware_sample_driver.c: fix coding style
  MAINTAINERS: Add ati_remote2 driver
  ...

Fixed up trivial conflicts in firmware_sample_driver.c
</content>
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<pre>
* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/juhl/trivial: (24 commits)
  DOC:  A couple corrections and clarifications in USB doc.
  Generate a slightly more informative error msg for bad HZ
  fix typo "is" -&gt; "if" in Makefile
  ext*: spelling fix prefered -&gt; preferred
  DOCUMENTATION:  Use newer DEFINE_SPINLOCK macro in docs.
  KEYS:  Fix the comment to match the file name in rxrpc-type.h.
  RAID: remove trailing space from printk line
  DMA engine: typo fixes
  Remove unused MAX_NODES_SHIFT
  MAINTAINERS: Clarify access to OCFS2 development mailing list.
  V4L: Storage class should be before const qualifier (sn9c102)
  V4L: Storage class should be before const qualifier
  sonypi: Storage class should be before const qualifier
  intel_menlow: Storage class should be before const qualifier
  DVB: Storage class should be before const qualifier
  arm: Storage class should be before const qualifier
  ALSA: Storage class should be before const qualifier
  acpi: Storage class should be before const qualifier
  firmware_sample_driver.c: fix coding style
  MAINTAINERS: Add ati_remote2 driver
  ...

Fixed up trivial conflicts in firmware_sample_driver.c
</pre>
</div>
</content>
</entry>
<entry>
<title>Generate a slightly more informative error msg for bad HZ</title>
<updated>2008-04-21T22:56:14+00:00</updated>
<author>
<name>Robert P. J. Day</name>
<email>rpjday@crashcourse.ca</email>
</author>
<published>2008-04-21T22:56:14+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=37679011c5a674eb80bff5c2b9b067bf16011d46'/>
<id>37679011c5a674eb80bff5c2b9b067bf16011d46</id>
<content type='text'>
Generate a slightly more informative error msg for bad HZ
 in include/linux/jiffies.h

Signed-off-by: Robert P. J. Day &lt;rpjday@crashcourse.ca&gt;
Signed-off-by: Jesper Juhl &lt;jesper.juhl@gmail.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Generate a slightly more informative error msg for bad HZ
 in include/linux/jiffies.h

Signed-off-by: Robert P. J. Day &lt;rpjday@crashcourse.ca&gt;
Signed-off-by: Jesper Juhl &lt;jesper.juhl@gmail.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>jiffies: add time_is_after_jiffies and others which compare with jiffies</title>
<updated>2008-04-21T05:59:51+00:00</updated>
<author>
<name>Dave Young</name>
<email>hidave.darkstar@gmail.com</email>
</author>
<published>2008-04-18T20:38:57+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=3f34d024c12e49fbce4009d094ae1d287084e511'/>
<id>3f34d024c12e49fbce4009d094ae1d287084e511</id>
<content type='text'>
Most of time_after like macros usages just compare jiffies and another number,
so here add some time_is_* macros for convenience.

Signed-off-by: Dave Young &lt;hidave.darkstar@gmail.com&gt;
Cc: Alan Cox &lt;alan@lxorguk.ukuu.org.uk&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Thomas Gleixner &lt;tglx@linutronix.de&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Most of time_after like macros usages just compare jiffies and another number,
so here add some time_is_* macros for convenience.

Signed-off-by: Dave Young &lt;hidave.darkstar@gmail.com&gt;
Cc: Alan Cox &lt;alan@lxorguk.ukuu.org.uk&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Thomas Gleixner &lt;tglx@linutronix.de&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>time: fix typo in comments</title>
<updated>2008-02-08T17:22:29+00:00</updated>
<author>
<name>Li Zefan</name>
<email>lizf@cn.fujitsu.com</email>
</author>
<published>2008-02-08T12:19:25+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=3eb056764dd806bbe84eb604e45e7470feeaafd8'/>
<id>3eb056764dd806bbe84eb604e45e7470feeaafd8</id>
<content type='text'>
Fix typo in comments.

BTW: I have to fix coding style in arch/ia64/kernel/time.c also, otherwise
checkpatch.pl will be complaining.

Signed-off-by: Li Zefan &lt;lizf@cn.fujitsu.com&gt;
Cc: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Cc: Ingo Molnar &lt;mingo@elte.hu&gt;
Cc: john stultz &lt;johnstul@us.ibm.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Fix typo in comments.

BTW: I have to fix coding style in arch/ia64/kernel/time.c also, otherwise
checkpatch.pl will be complaining.

Signed-off-by: Li Zefan &lt;lizf@cn.fujitsu.com&gt;
Cc: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Cc: Ingo Molnar &lt;mingo@elte.hu&gt;
Cc: john stultz &lt;johnstul@us.ibm.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>timers: don't #error on higher HZ values</title>
<updated>2008-01-25T20:08:34+00:00</updated>
<author>
<name>Pavel Machek</name>
<email>pavel@ucw.cz</email>
</author>
<published>2008-01-25T20:08:34+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=e118adef232e637a8f091c1ded2fbf44fcf3ecc8'/>
<id>e118adef232e637a8f091c1ded2fbf44fcf3ecc8</id>
<content type='text'>
For some crazy reason (trying to work around hw problem in i810) I wanted
to use HZ around 4000.

Signed-off-by: Pavel Machek &lt;pavel@suse.cz&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Ingo Molnar &lt;mingo@elte.hu&gt;
</content>
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<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
For some crazy reason (trying to work around hw problem in i810) I wanted
to use HZ around 4000.

Signed-off-by: Pavel Machek &lt;pavel@suse.cz&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Ingo Molnar &lt;mingo@elte.hu&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>slow down printk during boot</title>
<updated>2007-10-16T16:42:49+00:00</updated>
<author>
<name>Randy Dunlap</name>
<email>rdunlap@xenotime.net</email>
</author>
<published>2007-10-16T08:23:46+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=bfe8df3d314bddf30758bd738e0087e80964760c'/>
<id>bfe8df3d314bddf30758bd738e0087e80964760c</id>
<content type='text'>
Optionally add a boot delay after each kernel printk() call, crudely
measured in milliseconds, with a maximum delay of 10 seconds per printk.

Enable CONFIG_BOOT_PRINTK_DELAY=y and then add (e.g.):
"lpj=loops_per_jiffy boot_delay=100"
to the kernel command line.

It has been useful in cases like "during boot, my machine just reboots or the
screen goes black" by slowing down printk, (and adding initcall_debug), we can
usually see the last thing that happened before the lights went out which is
usually a valuable clue.

[akpm@linux-foundation.org: not all architectures implement CONFIG_HZ]
[akpm@linux-foundation.org: fix lots of stuff]
[bunk@stusta.de: kernel/printk.c: make 2 variables static]
[heiko.carstens@de.ibm.com: fix slow down printk on boot compile error]
Signed-off-by: Randy Dunlap &lt;rdunlap@xenotime.net&gt;
Signed-off-by: Dave Jones &lt;davej@redhat.com&gt;
Signed-off-by: Adrian Bunk &lt;bunk@stusta.de&gt;
Signed-off-by: Heiko Carstens &lt;heiko.carstens@de.ibm.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Optionally add a boot delay after each kernel printk() call, crudely
measured in milliseconds, with a maximum delay of 10 seconds per printk.

Enable CONFIG_BOOT_PRINTK_DELAY=y and then add (e.g.):
"lpj=loops_per_jiffy boot_delay=100"
to the kernel command line.

It has been useful in cases like "during boot, my machine just reboots or the
screen goes black" by slowing down printk, (and adding initcall_debug), we can
usually see the last thing that happened before the lights went out which is
usually a valuable clue.

[akpm@linux-foundation.org: not all architectures implement CONFIG_HZ]
[akpm@linux-foundation.org: fix lots of stuff]
[bunk@stusta.de: kernel/printk.c: make 2 variables static]
[heiko.carstens@de.ibm.com: fix slow down printk on boot compile error]
Signed-off-by: Randy Dunlap &lt;rdunlap@xenotime.net&gt;
Signed-off-by: Dave Jones &lt;davej@redhat.com&gt;
Signed-off-by: Adrian Bunk &lt;bunk@stusta.de&gt;
Signed-off-by: Heiko Carstens &lt;heiko.carstens@de.ibm.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge git://git.linux-nfs.org/pub/linux/nfs-2.6</title>
<updated>2007-10-15T17:47:35+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@woody.linux-foundation.org</email>
</author>
<published>2007-10-15T17:46:05+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=f4921aff5b174349bc36551f142a5dbac782ea3f'/>
<id>f4921aff5b174349bc36551f142a5dbac782ea3f</id>
<content type='text'>
* git://git.linux-nfs.org/pub/linux/nfs-2.6: (131 commits)
  NFSv4: Fix a typo in nfs_inode_reclaim_delegation
  NFS: Add a boot parameter to disable 64 bit inode numbers
  NFS: nfs_refresh_inode should clear cache_validity flags on success
  NFS: Fix a connectathon regression in NFSv3 and NFSv4
  NFS: Use nfs_refresh_inode() in ops that aren't expected to change the inode
  SUNRPC: Don't call xprt_release in call refresh
  SUNRPC: Don't call xprt_release() if call_allocate fails
  SUNRPC: Fix buggy UDP transmission
  [23/37] Clean up duplicate includes in
  [2.6 patch] net/sunrpc/rpcb_clnt.c: make struct rpcb_program static
  SUNRPC: Use correct type in buffer length calculations
  SUNRPC: Fix default hostname created in rpc_create()
  nfs: add server port to rpc_pipe info file
  NFS: Get rid of some obsolete macros
  NFS: Simplify filehandle revalidation
  NFS: Ensure that nfs_link() returns a hashed dentry
  NFS: Be strict about dentry revalidation when doing exclusive create
  NFS: Don't zap the readdir caches upon error
  NFS: Remove the redundant nfs_reval_fsid()
  NFSv3: Always use directory post-op attributes in nfs3_proc_lookup
  ...

Fix up trivial conflict due to sock_owned_by_user() cleanup manually in
net/sunrpc/xprtsock.c
</content>
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<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
* git://git.linux-nfs.org/pub/linux/nfs-2.6: (131 commits)
  NFSv4: Fix a typo in nfs_inode_reclaim_delegation
  NFS: Add a boot parameter to disable 64 bit inode numbers
  NFS: nfs_refresh_inode should clear cache_validity flags on success
  NFS: Fix a connectathon regression in NFSv3 and NFSv4
  NFS: Use nfs_refresh_inode() in ops that aren't expected to change the inode
  SUNRPC: Don't call xprt_release in call refresh
  SUNRPC: Don't call xprt_release() if call_allocate fails
  SUNRPC: Fix buggy UDP transmission
  [23/37] Clean up duplicate includes in
  [2.6 patch] net/sunrpc/rpcb_clnt.c: make struct rpcb_program static
  SUNRPC: Use correct type in buffer length calculations
  SUNRPC: Fix default hostname created in rpc_create()
  nfs: add server port to rpc_pipe info file
  NFS: Get rid of some obsolete macros
  NFS: Simplify filehandle revalidation
  NFS: Ensure that nfs_link() returns a hashed dentry
  NFS: Be strict about dentry revalidation when doing exclusive create
  NFS: Don't zap the readdir caches upon error
  NFS: Remove the redundant nfs_reval_fsid()
  NFSv3: Always use directory post-op attributes in nfs3_proc_lookup
  ...

Fix up trivial conflict due to sock_owned_by_user() cleanup manually in
net/sunrpc/xprtsock.c
</pre>
</div>
</content>
</entry>
<entry>
<title>jiffies: remove unused macros</title>
<updated>2007-10-12T21:04:23+00:00</updated>
<author>
<name>Chris Wright</name>
<email>chrisw@sous-sol.org</email>
</author>
<published>2007-10-12T21:04:23+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=5b94664a3a2a4f3c516a4a2f454f3c811cb25959'/>
<id>5b94664a3a2a4f3c516a4a2f454f3c811cb25959</id>
<content type='text'>
The x86 hpet cleanups allow removal of some unused macros.

Signed-off-by: Chris Wright &lt;chrisw@sous-sol.org&gt;
Signed-off-by: Ingo Molnar &lt;mingo@elte.hu&gt;
Signed-off-by: Arjan van de Ven &lt;arjan@linux.intel.com&gt;
Signed-off-by: Thomas Gleixner &lt;tglx@linutronix.de&gt;
</content>
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<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The x86 hpet cleanups allow removal of some unused macros.

Signed-off-by: Chris Wright &lt;chrisw@sous-sol.org&gt;
Signed-off-by: Ingo Molnar &lt;mingo@elte.hu&gt;
Signed-off-by: Arjan van de Ven &lt;arjan@linux.intel.com&gt;
Signed-off-by: Thomas Gleixner &lt;tglx@linutronix.de&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Re: [NFS] [PATCH] Attribute timeout handling and wrapping u32 jiffies</title>
<updated>2007-10-09T21:15:33+00:00</updated>
<author>
<name>Fabio Olive Leite</name>
<email>fleite@redhat.com</email>
</author>
<published>2007-07-27T01:59:00+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=c7e15961115028b99f6142266b5fb08acca0e8dd'/>
<id>c7e15961115028b99f6142266b5fb08acca0e8dd</id>
<content type='text'>
I would like to discuss the idea that the current checks for attribute
timeout using time_after are inadequate for 32bit architectures, since
time_after works correctly only when the two timestamps being compared
are within 2^31 jiffies of each other. The signed overflow caused by
comparing values more than 2^31 jiffies apart will flip the result,
causing incorrect assumptions of validity.

2^31 jiffies is a fairly large period of time (~25 days) when compared
to the lifetime of most kernel data structures, but for long lived NFS
mounts that can sit idle for months (think that for some reason autofs
cannot be used), it is easy to compare inode attribute timestamps with
very disparate or even bogus values (as in when jiffies have wrapped
many times, where the comparison doesn't even make sense).

Currently the code tests for attribute timeout by simply adding the
desired amount of jiffies to the stored timestamp and comparing that
with the current timestamp of obtained attribute data with time_after.
This is incorrect, as it returns true for the desired timeout period
and another full 2^31 range of jiffies.

In testing with artificial jumps (several small jumps, not one big
crank) of the jiffies I was able to reproduce a problem found in a
server with very long lived NFS mounts, where attributes would not be
refreshed even after touching files and directories in the server:

Initial uptime:
03:42:01 up 6 min, 0 users, load average: 0.01, 0.12, 0.07

NFS volume is mounted and time is advanced:
03:38:09 up 25 days, 2 min, 0 users, load average: 1.22, 1.05, 1.08

# ls -l /local/A/foo/bar /nfs/A/foo/bar
-rw-r--r--  1 root root 0 Dec 17 03:38 /local/A/foo/bar
-rw-r--r--  1 root root 0 Nov 22 00:36 /nfs/A/foo/bar

# touch /local/A/foo/bar

# ls -l /local/A/foo/bar /nfs/A/foo/bar
-rw-r--r--  1 root root 0 Dec 17 03:47 /local/A/foo/bar
-rw-r--r--  1 root root 0 Nov 22 00:36 /nfs/A/foo/bar

We can see the local mtime is updated, but the NFS mount still shows
the old value. The patch below makes it work:

Initial setup...
07:11:02 up 25 days, 1 min,  0 users,  load average: 0.15, 0.03, 0.04

# ls -l /local/A/foo/bar /nfs/A/foo/bar
-rw-r--r--  1 root root 0 Jan 11 07:11 /local/A/foo/bar
-rw-r--r--  1 root root 0 Jan 11 07:11 /nfs/A/foo/bar

# touch /local/A/foo/bar

# ls -l /local/A/foo/bar /nfs/A/foo/bar
-rw-r--r--  1 root root 0 Jan 11 07:14 /local/A/foo/bar
-rw-r--r--  1 root root 0 Jan 11 07:14 /nfs/A/foo/bar

Signed-off-by: Fabio Olive Leite &lt;fleite@redhat.com&gt;
Signed-off-by: Trond Myklebust &lt;Trond.Myklebust@netapp.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
I would like to discuss the idea that the current checks for attribute
timeout using time_after are inadequate for 32bit architectures, since
time_after works correctly only when the two timestamps being compared
are within 2^31 jiffies of each other. The signed overflow caused by
comparing values more than 2^31 jiffies apart will flip the result,
causing incorrect assumptions of validity.

2^31 jiffies is a fairly large period of time (~25 days) when compared
to the lifetime of most kernel data structures, but for long lived NFS
mounts that can sit idle for months (think that for some reason autofs
cannot be used), it is easy to compare inode attribute timestamps with
very disparate or even bogus values (as in when jiffies have wrapped
many times, where the comparison doesn't even make sense).

Currently the code tests for attribute timeout by simply adding the
desired amount of jiffies to the stored timestamp and comparing that
with the current timestamp of obtained attribute data with time_after.
This is incorrect, as it returns true for the desired timeout period
and another full 2^31 range of jiffies.

In testing with artificial jumps (several small jumps, not one big
crank) of the jiffies I was able to reproduce a problem found in a
server with very long lived NFS mounts, where attributes would not be
refreshed even after touching files and directories in the server:

Initial uptime:
03:42:01 up 6 min, 0 users, load average: 0.01, 0.12, 0.07

NFS volume is mounted and time is advanced:
03:38:09 up 25 days, 2 min, 0 users, load average: 1.22, 1.05, 1.08

# ls -l /local/A/foo/bar /nfs/A/foo/bar
-rw-r--r--  1 root root 0 Dec 17 03:38 /local/A/foo/bar
-rw-r--r--  1 root root 0 Nov 22 00:36 /nfs/A/foo/bar

# touch /local/A/foo/bar

# ls -l /local/A/foo/bar /nfs/A/foo/bar
-rw-r--r--  1 root root 0 Dec 17 03:47 /local/A/foo/bar
-rw-r--r--  1 root root 0 Nov 22 00:36 /nfs/A/foo/bar

We can see the local mtime is updated, but the NFS mount still shows
the old value. The patch below makes it work:

Initial setup...
07:11:02 up 25 days, 1 min,  0 users,  load average: 0.15, 0.03, 0.04

# ls -l /local/A/foo/bar /nfs/A/foo/bar
-rw-r--r--  1 root root 0 Jan 11 07:11 /local/A/foo/bar
-rw-r--r--  1 root root 0 Jan 11 07:11 /nfs/A/foo/bar

# touch /local/A/foo/bar

# ls -l /local/A/foo/bar /nfs/A/foo/bar
-rw-r--r--  1 root root 0 Jan 11 07:14 /local/A/foo/bar
-rw-r--r--  1 root root 0 Jan 11 07:14 /nfs/A/foo/bar

Signed-off-by: Fabio Olive Leite &lt;fleite@redhat.com&gt;
Signed-off-by: Trond Myklebust &lt;Trond.Myklebust@netapp.com&gt;
</pre>
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