Commit aaeb94eb authored Mar 07, 2023 by Christoph Hellwig Committed by Andrew Morton Apr 05, 2023

shmem: open code the page cache lookup in shmem_get_folio_gfp

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>

parent 81914aff

mm/shmem.c

+10 −4

Original line number	Diff line number	Diff line
		@@ -1880,12 +1880,10 @@ static int shmem_get_folio_gfp(struct inode *inode, pgoff_t index,
		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 @@ static int shmem_get_folio_gfp(struct inode *inode, pgoff_t index,
		}

		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))