diff options
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/highmem.h | 38 |
1 files changed, 38 insertions, 0 deletions
diff --git a/include/linux/highmem.h b/include/linux/highmem.h index be20cff4ba73..5ebd5e4dfbf8 100644 --- a/include/linux/highmem.h +++ b/include/linux/highmem.h @@ -484,6 +484,44 @@ static inline void memcpy_to_folio(struct folio *folio, size_t offset, } /** + * folio_zero_tail - Zero the tail of a folio. + * @folio: The folio to zero. + * @offset: The byte offset in the folio to start zeroing at. + * @kaddr: The address the folio is currently mapped to. + * + * If you have already used kmap_local_folio() to map a folio, written + * some data to it and now need to zero the end of the folio (and flush + * the dcache), you can use this function. If you do not have the + * folio kmapped (eg the folio has been partially populated by DMA), + * use folio_zero_range() or folio_zero_segment() instead. + * + * Return: An address which can be passed to kunmap_local(). + */ +static inline __must_check void *folio_zero_tail(struct folio *folio, + size_t offset, void *kaddr) +{ + size_t len = folio_size(folio) - offset; + + if (folio_test_highmem(folio)) { + size_t max = PAGE_SIZE - offset_in_page(offset); + + while (len > max) { + memset(kaddr, 0, max); + kunmap_local(kaddr); + len -= max; + offset += max; + max = PAGE_SIZE; + kaddr = kmap_local_folio(folio, offset); + } + } + + memset(kaddr, 0, len); + flush_dcache_folio(folio); + + return kaddr; +} + +/** * memcpy_from_file_folio - Copy some bytes from a file folio. * @to: The destination buffer. * @folio: The folio to copy from. |