+ shmem-minor-fixes-to-splice-read-implementation.patch added to mm-hotfixes-unstable branch

+ shmem-minor-fixes-to-splice-read-implementation.patch added to mm-hotfixes-unstable branch

[Andrew Morton]

The patch titled
     Subject: shmem: minor fixes to splice-read implementation
has been added to the -mm mm-hotfixes-unstable branch.  Its filename is
     shmem-minor-fixes-to-splice-read-implementation.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/shmem-minor-fixes-to-splice-read-implementation.patch

This patch will later appear in the mm-hotfixes-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Hugh Dickins <hughd@google.com>
Subject: shmem: minor fixes to splice-read implementation
Date: Sun, 23 Jul 2023 14:05:54 -0700 (PDT)

HWPoison: my reading of folio_test_hwpoison() is that it only tests the
head page of a large folio, whereas splice_folio_into_pipe() will splice
as much of the folio as it can: so for safety we should also check the
has_hwpoisoned flag, set if any of the folio's pages are hwpoisoned. 
(Perhaps that ugliness can be improved at the mm end later.)

The call to splice_zeropage_into_pipe() risked overrunning past EOF: ask
it for "part" not "len".

Link: https://lkml.kernel.org/r/32c72c9c-72a8-115f-407d-f0148f368@google.com
Fixes: bd194b187115 ("shmem: Implement splice-read")
Signed-off-by: Hugh Dickins <hughd@google.com>
Reviewed-by: David Howells <dhowells@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/shmem.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

--- a/mm/shmem.c~shmem-minor-fixes-to-splice-read-implementation
+++ a/mm/shmem.c
@@ -2796,7 +2796,8 @@ static ssize_t shmem_file_splice_read(st
 		if (*ppos >= i_size_read(inode))
 			break;
 
-		error = shmem_get_folio(inode, *ppos / PAGE_SIZE, &folio, SGP_READ);
+		error = shmem_get_folio(inode, *ppos / PAGE_SIZE, &folio,
+					SGP_READ);
 		if (error) {
 			if (error == -EINVAL)
 				error = 0;
@@ -2805,7 +2806,9 @@ static ssize_t shmem_file_splice_read(st
 		if (folio) {
 			folio_unlock(folio);
 
-			if (folio_test_hwpoison(folio)) {
+			if (folio_test_hwpoison(folio) ||
+			    (folio_test_large(folio) &&
+			     folio_test_has_hwpoisoned(folio))) {
 				error = -EIO;
 				break;
 			}
@@ -2841,7 +2844,7 @@ static ssize_t shmem_file_splice_read(st
 			folio_put(folio);
 			folio = NULL;
 		} else {
-			n = splice_zeropage_into_pipe(pipe, *ppos, len);
+			n = splice_zeropage_into_pipe(pipe, *ppos, part);
 		}
 
 		if (!n)
_

Patches currently in -mm which might be from hughd@google.com are

tmpfs-fix-documentation-of-noswap-and-huge-mount-options.patch
shmem-minor-fixes-to-splice-read-implementation.patch
mm-pagewalk-fix-efi_pgt_dump-of-espfix-area.patch
mm-userfaultfd-add-new-uffdio_poison-ioctl-fix.patch
mm-pgtable-add-rcu_read_lock-and-rcu_read_unlocks.patch
mm-pgtable-add-pae-safety-to-__pte_offset_map.patch
arm-adjust_pte-use-pte_offset_map_nolock.patch
powerpc-assert_pte_locked-use-pte_offset_map_nolock.patch
powerpc-add-pte_free_defer-for-pgtables-sharing-page.patch
sparc-add-pte_free_defer-for-pte_t-pgtable_t.patch
s390-add-pte_free_defer-for-pgtables-sharing-page.patch
mm-pgtable-add-pte_free_defer-for-pgtable-as-page.patch
mm-khugepaged-retract_page_tables-without-mmap-or-vma-lock.patch
mm-khugepaged-collapse_pte_mapped_thp-with-mmap_read_lock.patch
mm-khugepaged-delete-khugepaged_collapse_pte_mapped_thps.patch
mm-delete-mmap_write_trylock-and-vma_try_start_write.patch
mm-pgtable-notes-on-pte_offset_map.patch