[RFC 0/8] shmem: add support for blocksize > PAGE_SIZE

[Luis Chamberlain]

This is an initial attempt to add support for block size > PAGE_SIZE for tmpfs.
Why would you want this? It helps us experiment with higher order folio uses
with fs APIS and helps us test out corner cases which would likely need
to be accounted for sooner or later if and when filesystems enable support
for this. Better review early and burn early than continue on in the wrong
direction so looking for early feedback.

I have other patches to convert shmem_write_begin() and shmem_file_read_iter()
to folios too but those are not yet working. In the swap world the next
thing to look at would be to convert swap_cluster_readahead() to folios.

If folks want to experiment with tmpfs, brd or with things related to larger
block sizes I've put a branch up with this, Hannes's brd patches, and some
still work-in-progress patches on my large-block-20230421 branch [0]. Similarly
you can also use kdevops with CONFIG_QEMU_ENABLE_EXTRA_DRIVE_LARGEIO support
to get everything with just as that branch is used for that:

  make
  make bringup
  make linux

[0] https://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux-next.git/log/?h=large-block-20230421
[1] https://github.com/linux-kdevops/kdevops

Luis Chamberlain (8):
  shmem: replace BLOCKS_PER_PAGE with PAGE_SECTORS
  shmem: convert to use folio_test_hwpoison()
  shmem: account for high order folios
  shmem: add helpers to get block size
  shmem: account for larger blocks sizes for shmem_default_max_blocks()
  shmem: consider block size in shmem_default_max_inodes()
  shmem: add high order page support
  shmem: add support to customize block size on multiple PAGE_SIZE

 include/linux/shmem_fs.h |   3 +
 mm/shmem.c               | 146 +++++++++++++++++++++++++++++----------
 2 files changed, 114 insertions(+), 35 deletions(-)

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2.39.2