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Ram Tummala 4cd7ba16a0 mm: fix old/young bit handling in the faulting path 
Commit 3bd786f76d ("mm: convert do_set_pte() to set_pte_range()")
replaced do_set_pte() with set_pte_range() and that introduced a
regression in the following faulting path of non-anonymous vmas which
caused the PTE for the faulting address to be marked as old instead of
young.

handle_pte_fault()
  do_pte_missing()
    do_fault()
      do_read_fault() || do_cow_fault() || do_shared_fault()
        finish_fault()
          set_pte_range()

The polarity of prefault calculation is incorrect.  This leads to prefault
being incorrectly set for the faulting address.  The following check will
incorrectly mark the PTE old rather than young.  On some architectures
this will cause a double fault to mark it young when the access is
retried.

    if (prefault && arch_wants_old_prefaulted_pte())
        entry = pte_mkold(entry);

On a subsequent fault on the same address, the faulting path will see a
non NULL vmf->pte and instead of reaching the do_pte_missing() path, PTE
will then be correctly marked young in handle_pte_fault() itself.

Due to this bug, performance degradation in the fault handling path will
be observed due to unnecessary double faulting.

Link: https://lkml.kernel.org/r/20240710014539.746200-1-rtummala@nvidia.com
Fixes: 3bd786f76d ("mm: convert do_set_pte() to set_pte_range()")
Signed-off-by: Ram Tummala <rtummala@nvidia.com>
Reviewed-by: Yin Fengwei <fengwei.yin@intel.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Yin Fengwei <fengwei.yin@intel.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2024-07-26 14:33:09 -07:00
arch sysctl: treewide: constify the ctl_table argument of proc_handlers 2024-07-25 12:58:36 -07:00
block for-6.11/block-20240722 2024-07-22 11:32:05 -07:00
certs kbuild: use $(src) instead of $(srctree)/$(src) for source directory 2024-05-10 04:34:52 +09:00
crypto crypto: testmgr - generate power-of-2 lengths more often 2024-07-13 11:50:28 +12:00
Documentation dt-bindings: arm: update James Clark's email address 2024-07-26 14:32:50 -07:00
drivers A lot of networking people were at a conference last week, busy 2024-07-25 13:32:25 -07:00
fs sysctl: treewide: constify the ctl_table argument of proc_handlers 2024-07-25 12:58:36 -07:00
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init Kbuild updates for v6.11 2024-07-23 14:32:21 -07:00
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kernel A lot of networking people were at a conference last week, busy 2024-07-25 13:32:25 -07:00
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mm mm: fix old/young bit handling in the faulting path 2024-07-26 14:33:09 -07:00
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rust This pull request contains the following changes for UML: 2024-07-25 12:33:08 -07:00
samples Driver core changes for 6.11-rc1 2024-07-25 10:42:22 -07:00
scripts This pull request contains the following changes for UML: 2024-07-25 12:33:08 -07:00
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.rustfmt.toml
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MAINTAINERS MAINTAINERS: mailmap: update James Clark's email address 2024-07-26 14:32:35 -07:00
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README README: Fix spelling 2024-03-18 03:36:32 -06:00

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.