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commit 4cd7ba16a0afb36550eed7690e73d3e7a743fa96 upstream. Commit3bd786f76d("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> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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 Restructured Text 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.