diff options
Diffstat (limited to 'mm/shmem.c')
| -rw-r--r-- | mm/shmem.c | 31 |
1 files changed, 20 insertions, 11 deletions
diff --git a/mm/shmem.c b/mm/shmem.c index 529c9ad3e926..4b2fea33158e 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -2513,7 +2513,6 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) pgoff_t end_index; unsigned long nr, ret; loff_t i_size = i_size_read(inode); - bool got_page; end_index = i_size >> PAGE_SHIFT; if (index > end_index) @@ -2570,24 +2569,34 @@ static ssize_t shmem_file_read_iter(struct kiocb *iocb, struct iov_iter *to) */ if (!offset) mark_page_accessed(page); - got_page = true; + /* + * Ok, we have the page, and it's up-to-date, so + * now we can copy it to user space... + */ + ret = copy_page_to_iter(page, offset, nr, to); + put_page(page); + + } else if (iter_is_iovec(to)) { + /* + * Copy to user tends to be so well optimized, but + * clear_user() not so much, that it is noticeably + * faster to copy the zero page instead of clearing. + */ + ret = copy_page_to_iter(ZERO_PAGE(0), offset, nr, to); } else { - page = ZERO_PAGE(0); - got_page = false; + /* + * But submitting the same page twice in a row to + * splice() - or others? - can result in confusion: + * so don't attempt that optimization on pipes etc. + */ + ret = iov_iter_zero(nr, to); } - /* - * Ok, we have the page, and it's up-to-date, so - * now we can copy it to user space... - */ - ret = copy_page_to_iter(page, offset, nr, to); retval += ret; offset += ret; index += offset >> PAGE_SHIFT; offset &= ~PAGE_MASK; - if (got_page) - put_page(page); if (!iov_iter_count(to)) break; if (ret < nr) { |