From aaeb94eb86c58a89e70ae2dda46e137a72508ae3 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Tue, 7 Mar 2023 15:34:08 +0100 Subject: 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 Signed-off-by: Hugh Dickins Acked-by: Hugh Dickins Cc: Andreas Gruenbacher Cc: Matthew Wilcox (Oracle) Cc: Ryusuke Konishi Signed-off-by: Andrew Morton --- mm/shmem.c | 14 ++++++++++---- 1 file changed, 10 insertions(+), 4 deletions(-) (limited to 'mm/shmem.c') diff --git a/mm/shmem.c b/mm/shmem.c index 1549866c208f..93cb39852a16 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -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)) -- cgit v1.2.3