Commit d2a87be6 authored by Baolin Wang's avatar Baolin Wang Committed by Euler
Browse files

mm: shmem: fallback to page size splice if large folio has poisoned pages 

mainline inclusion
from mainline-v6.12-rc1
commit 729881ffd390797077cec0e573d33b4d724d70b3
category: feature
bugzilla: https://gitee.com/openeuler/kernel/issues/IBFSMJ

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=729881ffd390797077cec0e573d33b4d724d70b3

--------------------------------

The tmpfs has already supported the PMD-sized large folios, and splice()
can not read any pages if the large folio has a poisoned page, which is
not good as Matthew pointed out in a previous email[1]:

"so if we have hwpoison set on one page in a folio, we now can't read
bytes from any page in the folio?  That seems like we've made a bad
situation worse."

Thus add a fallback to the PAGE_SIZE splice() still allows reading normal
pages if the large folio has hwpoisoned pages.

[1] https://lore.kernel.org/all/Zw_d0EVAJkpNJEbA@casper.infradead.org/

[baolin.wang@linux.alibaba.com: code layout cleaup, per dhowells]
  Link: https://lkml.kernel.org/r/32dd938c-3531-49f7-93e4-b7ff21fec569@linux.alibaba.com
Link: https://lkml.kernel.org/r/e3737fbd5366c4de4337bf5f2044817e77a5235b.1729915173.git.baolin.wang@linux.alibaba.com


Signed-off-by: default avatarBaolin Wang <baolin.wang@linux.alibaba.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: David Howells <dhowells@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarWang Lian <dev01404@linx-info.com>
---
parent 3649ebdb

mm/shmem.c

+30 −8
Original line number Diff line number Diff line
@@ -3267,11 +3267,16 @@ static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos, 
	len = min_t(size_t, len, npages * PAGE_SIZE);



	do {

		bool fallback_page_splice = false;

		struct page *page = NULL;

		pgoff_t index;

		size_t size;



		if (*ppos >= i_size_read(inode))

			break;



		error = shmem_get_folio(inode, *ppos / PAGE_SIZE, 0, &folio,

					SGP_READ);

		index = *ppos >> PAGE_SHIFT;

		error = shmem_get_folio(inode, index, 0, &folio, SGP_READ);

		if (error) {

			if (error == -EINVAL)

				error = 0;
@@ -3280,12 +3285,15 @@ static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos, 
		if (folio) {

			folio_unlock(folio);



			if (folio_test_hwpoison(folio) ||

			    (folio_test_large(folio) &&

			     folio_test_has_hwpoisoned(folio))) {

			page = folio_file_page(folio, index);

			if (PageHWPoison(page)) {

				error = -EIO;

				break;

			}



			if (folio_test_large(folio) &&

			    folio_test_has_hwpoisoned(folio))

				fallback_page_splice = true;

		}



		/*
@@ -3299,7 +3307,17 @@ static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos, 
		isize = i_size_read(inode);

		if (unlikely(*ppos >= isize))

			break;

		part = min_t(loff_t, isize - *ppos, len);

		/*

		 * Fallback to PAGE_SIZE splice if the large folio has hwpoisoned

		 * pages.

		 */

		size = len;

		if (unlikely(fallback_page_splice)) {

			size_t offset = *ppos & ~PAGE_MASK;



			size = umin(size, PAGE_SIZE - offset);

		}

		part = min_t(loff_t, isize - *ppos, size);



		if (folio) {

			/*
@@ -3307,8 +3325,12 @@ static ssize_t shmem_file_splice_read(struct file *in, loff_t *ppos, 
			 * virtual addresses, take care about potential aliasing

			 * before reading the page on the kernel side.

			 */

			if (mapping_writably_mapped(mapping))

			if (mapping_writably_mapped(mapping)) {

				if (likely(!fallback_page_splice))

					flush_dcache_folio(folio);

				else

					flush_dcache_page(page);

			}

			folio_mark_accessed(folio);

			/*

			 * Ok, we have the page, and it's up-to-date, so we can