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mm: shmem: add large folio support for tmpfs

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Add large folio support for tmpfs write and fallocate paths matching the
same high order preference mechanism used in the iomap buffered IO path as
used in __filemap_get_folio().

Add shmem_mapping_size_orders() to get a hint for the orders of the folio
based on the file size which takes care of the mapping requirements.

Traditionally, tmpfs only supported PMD-sized large folios.  However
nowadays with other file systems supporting any sized large folios, and
extending anonymous to support mTHP, we should not restrict tmpfs to
allocating only PMD-sized large folios, making it more special.  Instead,
we should allow tmpfs can allocate any sized large folios.

Considering that tmpfs already has the 'huge=' option to control the
PMD-sized large folios allocation, we can extend the 'huge=' option to
allow any sized large folios.  The semantics of the 'huge=' mount option
are:

huge=never: no any sized large folios
huge=always: any sized large folios
huge=within_size: like 'always' but respect the i_size
huge=advise: like 'always' if requested with madvise()

Note: for tmpfs mmap() faults, due to the lack of a write size hint, still
allocate the PMD-sized huge folios if huge=always/within_size/advise is
set.

Moreover, the 'deny' and 'force' testing options controlled by
'/sys/kernel/mm/transparent_hugepage/shmem_enabled', still retain the same
semantics.  The 'deny' can disable any sized large folios for tmpfs, while
the 'force' can enable PMD sized large folios for tmpfs.

Link: https://lkml.kernel.org/r/035bf55fbdebeff65f5cb2cdb9907b7d632c3228.1732779148.git.baolin.wang@linux.alibaba.com
Co-developed-by: Daniel Gomez <da.gomez@samsung.com>
Signed-off-by: Daniel Gomez <da.gomez@samsung.com>
Signed-off-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Barry Song <baohua@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Lance Yang <ioworker0@gmail.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Baolin Wang 2024-11-28 15:40:41 +08:00 • committed by Andrew Morton
commit acd7ccb284
1 changed files with 81 additions and 18 deletions
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