On Mon 22-05-23 21:57:44, David Howells wrote: > This will pin pages or leave them unaltered rather than getting a ref on > them as appropriate to the iterator. > > The pages need to be pinned for DIO rather than having refs taken on them > to prevent VM copy-on-write from malfunctioning during a concurrent fork() > (the result of the I/O could otherwise end up being visible to/affected by > the child process). > > Signed-off-by: David Howells <dhowells@xxxxxxxxxx> > Reviewed-by: Christoph Hellwig <hch@xxxxxx> > Reviewed-by: John Hubbard <jhubbard@xxxxxxxxxx> > cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx> > cc: Jens Axboe <axboe@xxxxxxxxx> > cc: Jan Kara <jack@xxxxxxx> > cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> > cc: Logan Gunthorpe <logang@xxxxxxxxxxxx> > cc: linux-block@xxxxxxxxxxxxxxx > --- Looks good. Feel free to add: Reviewed-by: Jan Kara <jack@xxxxxxx> Honza > > Notes: > ver #10) > - Drop bio_set_cleanup_mode(), open coding it instead. > > ver #8) > - Split the patch up a bit [hch]. > - We should only be using pinned/non-pinned pages and not ref'd pages, > so adjust the comments appropriately. > > ver #7) > - Don't treat BIO_PAGE_REFFED/PINNED as being the same as FOLL_GET/PIN. > > ver #5) > - Transcribe the FOLL_* flags returned by iov_iter_extract_pages() to > BIO_* flags and got rid of bi_cleanup_mode. > - Replaced BIO_NO_PAGE_REF to BIO_PAGE_REFFED in the preceding patch. > > block/blk-map.c | 23 +++++++++++------------ > 1 file changed, 11 insertions(+), 12 deletions(-) > > diff --git a/block/blk-map.c b/block/blk-map.c > index 33d9f6e89ba6..3551c3ff17cf 100644 > --- a/block/blk-map.c > +++ b/block/blk-map.c > @@ -281,22 +281,21 @@ static int bio_map_user_iov(struct request *rq, struct iov_iter *iter, > > if (blk_queue_pci_p2pdma(rq->q)) > extraction_flags |= ITER_ALLOW_P2PDMA; > + if (iov_iter_extract_will_pin(iter)) > + bio_set_flag(bio, BIO_PAGE_PINNED); > > - bio_set_flag(bio, BIO_PAGE_REFFED); > while (iov_iter_count(iter)) { > - struct page **pages, *stack_pages[UIO_FASTIOV]; > + struct page *stack_pages[UIO_FASTIOV]; > + struct page **pages = stack_pages; > ssize_t bytes; > size_t offs; > int npages; > > - if (nr_vecs <= ARRAY_SIZE(stack_pages)) { > - pages = stack_pages; > - bytes = iov_iter_get_pages(iter, pages, LONG_MAX, > - nr_vecs, &offs, extraction_flags); > - } else { > - bytes = iov_iter_get_pages_alloc(iter, &pages, > - LONG_MAX, &offs, extraction_flags); > - } > + if (nr_vecs > ARRAY_SIZE(stack_pages)) > + pages = NULL; > + > + bytes = iov_iter_extract_pages(iter, &pages, LONG_MAX, > + nr_vecs, extraction_flags, &offs); > if (unlikely(bytes <= 0)) { > ret = bytes ? bytes : -EFAULT; > goto out_unmap; > @@ -318,7 +317,7 @@ static int bio_map_user_iov(struct request *rq, struct iov_iter *iter, > if (!bio_add_hw_page(rq->q, bio, page, n, offs, > max_sectors, &same_page)) { > if (same_page) > - put_page(page); > + bio_release_page(bio, page); > break; > } > > @@ -330,7 +329,7 @@ static int bio_map_user_iov(struct request *rq, struct iov_iter *iter, > * release the pages we didn't map into the bio, if any > */ > while (j < npages) > - put_page(pages[j++]); > + bio_release_page(bio, pages[j++]); > if (pages != stack_pages) > kvfree(pages); > /* couldn't stuff something into bio? */ > -- Jan Kara <jack@xxxxxxxx> SUSE Labs, CR