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shmem: open code the page cache lookup in shmem_get_folio_gfp

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Use the very low level filemap_get_entry helper to look up the entry in
the xarray, and then:

 - don't bother locking the folio if only doing a userfault notification
 - open code locking the page and checking for truncation in a related
   code block

This will allow to eventually remove the FGP_ENTRY flag.

[hughd@google.com: adjust the new comment line]
  Link: https://lkml.kernel.org/r/af178ebb-1076-a38c-1dc1-2a37ccce4a3@google.com
Link: https://lkml.kernel.org/r/20230307143410.28031-6-hch@lst.de
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Hugh Dickins <hughd@google.com>
Acked-by: Hugh Dickins <hughd@google.com>
Cc: Andreas Gruenbacher <agruenba@redhat.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Christoph Hellwig 2023-03-07 15:34:08 +01:00 committed by Andrew Morton
parent 81914aff84
commit aaeb94eb86
1 changed files with 10 additions and 4 deletions
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14
mm/shmem.c
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@ -1880,12 +1880,10 @@ repeat:
sbinfo = SHMEM_SB(inode->i_sb);
charge_mm = vma ? vma->vm_mm : NULL;
folio = __filemap_get_folio(mapping, index, FGP_ENTRY | FGP_LOCK, 0);
folio = filemap_get_entry(mapping, index);
if (folio && vma && userfaultfd_minor(vma)) {
if (!xa_is_value(folio)) {
folio_unlock(folio);
if (!xa_is_value(folio))
folio_put(folio);
}
*fault_type = handle_userfault(vmf, VM_UFFD_MINOR);
return 0;
}
@ -1901,6 +1899,14 @@ repeat:
}
if (folio) {
folio_lock(folio);
/* Has the folio been truncated or swapped out? */
if (unlikely(folio->mapping != mapping)) {
folio_unlock(folio);
folio_put(folio);
goto repeat;
}
if (sgp == SGP_WRITE)
folio_mark_accessed(folio);
if (folio_test_uptodate(folio))