summaryrefslogtreecommitdiff
path: root/lib
diff options
context:
space:
mode:
authorHugh Dickins <hughd@google.com>2024-10-28 01:23:23 +0300
committerChristian Brauner <brauner@kernel.org>2024-10-28 15:39:35 +0300
commitc749d9b7ebbc5716af7a95f7768634b30d9446ec (patch)
tree21dfcaa2e437f49e3b26f5faaf10ccadac91e888 /lib
parentf19910006effbd08398de79ca0233ea7e480616a (diff)
downloadlinux-c749d9b7ebbc5716af7a95f7768634b30d9446ec.tar.xz
iov_iter: fix copy_page_from_iter_atomic() if KMAP_LOCAL_FORCE_MAP
generic/077 on x86_32 CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP=y with highmem, on huge=always tmpfs, issues a warning and then hangs (interruptibly): WARNING: CPU: 5 PID: 3517 at mm/highmem.c:622 kunmap_local_indexed+0x62/0xc9 CPU: 5 UID: 0 PID: 3517 Comm: cp Not tainted 6.12.0-rc4 #2 ... copy_page_from_iter_atomic+0xa6/0x5ec generic_perform_write+0xf6/0x1b4 shmem_file_write_iter+0x54/0x67 Fix copy_page_from_iter_atomic() by limiting it in that case (include/linux/skbuff.h skb_frag_must_loop() does similar). But going forward, perhaps CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP is too surprising, has outlived its usefulness, and should just be removed? Fixes: 908a1ad89466 ("iov_iter: Handle compound highmem pages in copy_page_from_iter_atomic()") Signed-off-by: Hugh Dickins <hughd@google.com> Link: https://lore.kernel.org/r/dd5f0c89-186e-18e1-4f43-19a60f5a9774@google.com Reviewed-by: Christoph Hellwig <hch@lst.de> Cc: stable@vger.kernel.org Signed-off-by: Christian Brauner <brauner@kernel.org>
Diffstat (limited to 'lib')
-rw-r--r--lib/iov_iter.c6
1 files changed, 4 insertions, 2 deletions
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index cc4b5541eef8..908e75a28d90 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -461,6 +461,8 @@ size_t copy_page_from_iter_atomic(struct page *page, size_t offset,
size_t bytes, struct iov_iter *i)
{
size_t n, copied = 0;
+ bool uses_kmap = IS_ENABLED(CONFIG_DEBUG_KMAP_LOCAL_FORCE_MAP) ||
+ PageHighMem(page);
if (!page_copy_sane(page, offset, bytes))
return 0;
@@ -471,7 +473,7 @@ size_t copy_page_from_iter_atomic(struct page *page, size_t offset,
char *p;
n = bytes - copied;
- if (PageHighMem(page)) {
+ if (uses_kmap) {
page += offset / PAGE_SIZE;
offset %= PAGE_SIZE;
n = min_t(size_t, n, PAGE_SIZE - offset);
@@ -482,7 +484,7 @@ size_t copy_page_from_iter_atomic(struct page *page, size_t offset,
kunmap_atomic(p);
copied += n;
offset += n;
- } while (PageHighMem(page) && copied != bytes && n > 0);
+ } while (uses_kmap && copied != bytes && n > 0);
return copied;
}