From 99c79f6692ccdc42e04deea8a36e22bb48168a62 Mon Sep 17 00:00:00 2001 From: Aleix Roca Nonell Date: Thu, 15 Aug 2019 14:03:22 +0200 Subject: [PATCH] io_uring: fix manual setup of iov_iter for fixed buffers Commit bd11b3a391e3 ("io_uring: don't use iov_iter_advance() for fixed buffers") introduced an optimization to avoid using the slow iov_iter_advance by manually populating the iov_iter iterator in some cases. However, the computation of the iterator count field was erroneous: The first bvec was always accounted for an extent of page size even if the bvec length was smaller. In consequence, some I/O operations on fixed buffers were unable to operate on the full extent of the buffer, consistently skipping some bytes at the end of it. Fixes: bd11b3a391e3 ("io_uring: don't use iov_iter_advance() for fixed buffers") Cc: stable@vger.kernel.org Signed-off-by: Aleix Roca Nonell Signed-off-by: Jens Axboe --- fs/io_uring.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/fs/io_uring.c b/fs/io_uring.c index d542f1cf4428..aa25b5bbd4ae 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -1097,10 +1097,8 @@ static int io_import_fixed(struct io_ring_ctx *ctx, int rw, iter->bvec = bvec + seg_skip; iter->nr_segs -= seg_skip; - iter->count -= (seg_skip << PAGE_SHIFT); + iter->count -= bvec->bv_len + offset; iter->iov_offset = offset & ~PAGE_MASK; - if (iter->iov_offset) - iter->count -= iter->iov_offset; } } -- 2.30.2