From 950626d92c8b29118e4a7d6b9adb63be52ad5cb6 Mon Sep 17 00:00:00 2001 From: Christoph Hellwig Date: Tue, 7 Mar 2023 15:34:08 +0100 Subject: [PATCH] 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. Link: https://lkml.kernel.org/r/20230307143410.28031-6-hch@lst.de Signed-off-by: Christoph Hellwig 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(-) diff --git a/mm/shmem.c b/mm/shmem.c index e56b4addc801..e801e978af69 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1883,12 +1883,10 @@ 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; } @@ -1904,6 +1902,14 @@ repeat: } if (folio) { + folio_lock(folio); + + /* Has the page been truncated? */ + 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)) -- 2.50.1