Message ID | 20230124170108.1070389-9-dhowells@redhat.com (mailing list archive) |
---|---|
State | New, archived |
Headers | show |
Series | iov_iter: Improve page extraction (pin or just list) | expand |
On Tue, Jan 24, 2023 at 05:01:08PM +0000, 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). Reviewed-by: Christoph Hellwig <hch@lst.de>
On 1/24/23 09:01, 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@redhat.com> > cc: Al Viro <viro@zeniv.linux.org.uk> > cc: Jens Axboe <axboe@kernel.dk> > cc: Jan Kara <jack@suse.cz> > cc: Christoph Hellwig <hch@lst.de> > cc: Matthew Wilcox <willy@infradead.org> > cc: Logan Gunthorpe <logang@deltatee.com> > cc: linux-block@vger.kernel.org > --- > > Notes: > 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 | 22 ++++++++++------------ > 1 file changed, 10 insertions(+), 12 deletions(-) > Reviewed-by: John Hubbard <jhubbard@nvidia.com> thanks,
diff --git a/block/blk-map.c b/block/blk-map.c index 0e2b0a861ba3..4e22dccdbe9b 100644 --- a/block/blk-map.c +++ b/block/blk-map.c @@ -282,21 +282,19 @@ 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; - bio_set_flag(bio, BIO_PAGE_REFFED); + bio_set_cleanup_mode(bio, iter); 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 +316,7 @@ 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 +328,7 @@ 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? */
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@redhat.com> cc: Al Viro <viro@zeniv.linux.org.uk> cc: Jens Axboe <axboe@kernel.dk> cc: Jan Kara <jack@suse.cz> cc: Christoph Hellwig <hch@lst.de> cc: Matthew Wilcox <willy@infradead.org> cc: Logan Gunthorpe <logang@deltatee.com> cc: linux-block@vger.kernel.org --- Notes: 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 | 22 ++++++++++------------ 1 file changed, 10 insertions(+), 12 deletions(-)