The tmpfs has already supported the PMD-sized large folios, and splice() can not read any subpages if the large folio has a poisoned subpage, which is not good as we discussed in previous mail[1]. Thus adding a fallback to the PAGE_SIZE splice() still allows reading normal subpages if the large folio has hwpoisoned subpages. [1] https://lore.kernel.org/all/Zw_d0EVAJkpNJEbA@xxxxxxxxxxxxxxxxxxxx/ Signed-off-by: Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> --- mm/shmem.c | 39 +++++++++++++++++++++++++++++++-------- 1 file changed, 31 insertions(+), 8 deletions(-) diff --git a/mm/shmem.c b/mm/shmem.c index 1bef6e32a1fa..79010e636056 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -3291,11 +3291,16 @@ 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; @@ -3304,12 +3309,15 @@ 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; } /* @@ -3323,7 +3331,18 @@ 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 + * subpages. + */ + if (likely(!fallback_page_splice)) { + size = len; + } else { + size_t offset = *ppos & ~PAGE_MASK; + + size = min_t(loff_t, PAGE_SIZE - offset, len); + } + part = min_t(loff_t, isize - *ppos, size); if (folio) { /* @@ -3331,8 +3350,12 @@ 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)) - flush_dcache_folio(folio); + 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 -- 2.39.3
