| Message ID | 20190815120322.GA19630@rocks (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | io_uring: fix manual setup of iov_iter for fixed buffers | expand |
On 8/15/19 6:03 AM, Aleix Roca Nonell wrote: > 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. Applied, thanks.
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; } }
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 <aleix.rocanonell@bsc.es> --- fs/io_uring.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-)