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Instead of keeping different paths of splitting the entry before the swap in start, move the entry splitting after the swapin has put the folio in swap cache (or set the SWAP_HAS_CACHE bit). This way we only need one place and one unified way to split the large entry. Whenever swapin brought in a folio smaller than the shmem swap entry, split the entry and recalculate the entry and index for verification. This removes duplicated codes and function calls, reduces LOC, and the split is less racy as it's guarded by swap cache now. So it will have a lower chance of repeated faults due to raced split. The compiler is also able to optimize the coder further: bloat-o-meter results with GCC 14: With DEBUG_SECTION_MISMATCH (-fno-inline-functions-called-once): ./scripts/bloat-o-meter mm/shmem.o.old mm/shmem.o add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-143 (-143) Function old new delta shmem_swapin_folio 2358 2215 -143 Total: Before=32933, After=32790, chg -0.43% With !DEBUG_SECTION_MISMATCH: add/remove: 0/1 grow/shrink: 1/0 up/down: 1069/-749 (320) Function old new delta shmem_swapin_folio 2871 3940 +1069 shmem_split_large_entry.isra 749 - -749 Total: Before=32806, After=33126, chg +0.98% Since shmem_split_large_entry is only called in one place now. The compiler will either generate more compact code, or inlined it for better performance. Link: https://lkml.kernel.org/r/20250728075306.12704-5-ryncsn@gmail.com Signed-off-by: Kairui Song <kasong@tencent.com> Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com> Tested-by: Baolin Wang <baolin.wang@linux.alibaba.com> Cc: Baoquan He <bhe@redhat.com> Cc: Barry Song <baohua@kernel.org> Cc: Chris Li <chrisl@kernel.org> Cc: Dev Jain <dev.jain@arm.com> Cc: Hugh Dickins <hughd@google.com> Cc: Kemeng Shi <shikemeng@huaweicloud.com> Cc: Matthew Wilcox (Oracle) <willy@infradead.org> Cc: Nhat Pham <nphamcs@gmail.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.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 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.