From f550ee9b85fd47f85e31965b908a7c1044c531aa Mon Sep 17 00:00:00 2001 From: Jan Kara Date: Tue, 26 Nov 2019 09:28:47 -0800 Subject: iomap: Do not create fake iter in iomap_dio_bio_actor() iomap_dio_bio_actor() copies iter to a local variable and then limits it to a file extent we have mapped. When IO is submitted, iomap_dio_bio_actor() advances the original iter while the copied iter is advanced inside bio_iov_iter_get_pages(). This logic is non-obvious especially because both iters still point to same shared structures (such as pipe info) so if iov_iter_advance() changes anything in the shared structure, this scheme breaks. Let's just truncate and reexpand the original iter as needed instead of playing games with copying iters and keeping them in sync. Signed-off-by: Jan Kara Reviewed-by: Darrick J. Wong Signed-off-by: Darrick J. Wong Reviewed-by: Christoph Hellwig --- fs/iomap/direct-io.c | 31 ++++++++++++++++++------------- 1 file changed, 18 insertions(+), 13 deletions(-) (limited to 'fs') diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c index 420c0c82f0ac..b75cd0b0609b 100644 --- a/fs/iomap/direct-io.c +++ b/fs/iomap/direct-io.c @@ -201,12 +201,12 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length, unsigned int blkbits = blksize_bits(bdev_logical_block_size(iomap->bdev)); unsigned int fs_block_size = i_blocksize(inode), pad; unsigned int align = iov_iter_alignment(dio->submit.iter); - struct iov_iter iter; struct bio *bio; bool need_zeroout = false; bool use_fua = false; int nr_pages, ret = 0; size_t copied = 0; + size_t orig_count; if ((pos | length | align) & ((1 << blkbits) - 1)) return -EINVAL; @@ -236,15 +236,18 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length, } /* - * Operate on a partial iter trimmed to the extent we were called for. - * We'll update the iter in the dio once we're done with this extent. + * Save the original count and trim the iter to just the extent we + * are operating on right now. The iter will be re-expanded once + * we are done. */ - iter = *dio->submit.iter; - iov_iter_truncate(&iter, length); + orig_count = iov_iter_count(dio->submit.iter); + iov_iter_truncate(dio->submit.iter, length); - nr_pages = iov_iter_npages(&iter, BIO_MAX_PAGES); - if (nr_pages <= 0) - return nr_pages; + nr_pages = iov_iter_npages(dio->submit.iter, BIO_MAX_PAGES); + if (nr_pages <= 0) { + ret = nr_pages; + goto out; + } if (need_zeroout) { /* zero out from the start of the block to the write offset */ @@ -257,7 +260,8 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length, size_t n; if (dio->error) { iov_iter_revert(dio->submit.iter, copied); - return 0; + copied = ret = 0; + goto out; } bio = bio_alloc(GFP_KERNEL, nr_pages); @@ -268,7 +272,7 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length, bio->bi_private = dio; bio->bi_end_io = iomap_dio_bio_end_io; - ret = bio_iov_iter_get_pages(bio, &iter); + ret = bio_iov_iter_get_pages(bio, dio->submit.iter); if (unlikely(ret)) { /* * We have to stop part way through an IO. We must fall @@ -294,13 +298,11 @@ iomap_dio_bio_actor(struct inode *inode, loff_t pos, loff_t length, bio_set_pages_dirty(bio); } - iov_iter_advance(dio->submit.iter, n); - dio->size += n; pos += n; copied += n; - nr_pages = iov_iter_npages(&iter, BIO_MAX_PAGES); + nr_pages = iov_iter_npages(dio->submit.iter, BIO_MAX_PAGES); iomap_dio_submit_bio(dio, iomap, bio); } while (nr_pages); @@ -318,6 +320,9 @@ zero_tail: if (pad) iomap_dio_zero(dio, iomap, pos, fs_block_size - pad); } +out: + /* Undo iter limitation to current extent */ + iov_iter_reexpand(dio->submit.iter, orig_count - copied); if (copied) return copied; return ret; -- cgit v1.2.3 From 88cfd30e188fcf6fd8304586c936a6f22fb665e5 Mon Sep 17 00:00:00 2001 From: Johannes Thumshirn Date: Tue, 26 Nov 2019 09:28:47 -0800 Subject: iomap: remove unneeded variable in iomap_dio_rw() The 'start' variable indicates the start of a filemap and is set to the iocb's position, which we have already cached as 'pos', upon function entry. 'pos' is used as a cursor indicating the current position and updated later in iomap_dio_rw(), but not before the last use of 'start'. Remove 'start' as it's synonym for 'pos' before we're entering the loop calling iomapp_apply(). Signed-off-by: Johannes Thumshirn Reviewed-by: Christoph Hellwig Reviewed-by: Darrick J. Wong Signed-off-by: Darrick J. Wong --- fs/iomap/direct-io.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'fs') diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c index b75cd0b0609b..23837926c0c5 100644 --- a/fs/iomap/direct-io.c +++ b/fs/iomap/direct-io.c @@ -405,7 +405,7 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter, struct address_space *mapping = iocb->ki_filp->f_mapping; struct inode *inode = file_inode(iocb->ki_filp); size_t count = iov_iter_count(iter); - loff_t pos = iocb->ki_pos, start = pos; + loff_t pos = iocb->ki_pos; loff_t end = iocb->ki_pos + count - 1, ret = 0; unsigned int flags = IOMAP_DIRECT; struct blk_plug plug; @@ -461,14 +461,14 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter, } if (iocb->ki_flags & IOCB_NOWAIT) { - if (filemap_range_has_page(mapping, start, end)) { + if (filemap_range_has_page(mapping, pos, end)) { ret = -EAGAIN; goto out_free_dio; } flags |= IOMAP_NOWAIT; } - ret = filemap_write_and_wait_range(mapping, start, end); + ret = filemap_write_and_wait_range(mapping, pos, end); if (ret) goto out_free_dio; @@ -479,7 +479,7 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter, * pretty crazy thing to do, so we don't support it 100%. */ ret = invalidate_inode_pages2_range(mapping, - start >> PAGE_SHIFT, end >> PAGE_SHIFT); + pos >> PAGE_SHIFT, end >> PAGE_SHIFT); if (ret) dio_warn_stale_pagecache(iocb->ki_filp); ret = 0; -- cgit v1.2.3