diff options
| -rw-r--r-- | include/linux/uio.h | 6 | ||||
| -rw-r--r-- | lib/iov_iter.c | 63 |
2 files changed, 68 insertions, 1 deletions
diff --git a/include/linux/uio.h b/include/linux/uio.h index 804e34c6f981..f2d36a3d3005 100644 --- a/include/linux/uio.h +++ b/include/linux/uio.h @@ -39,7 +39,10 @@ struct iov_iter { }; union { unsigned long nr_segs; - int idx; + struct { + int idx; + int start_idx; + }; }; }; @@ -81,6 +84,7 @@ unsigned long iov_shorten(struct iovec *iov, unsigned long nr_segs, size_t to); size_t iov_iter_copy_from_user_atomic(struct page *page, struct iov_iter *i, unsigned long offset, size_t bytes); void iov_iter_advance(struct iov_iter *i, size_t bytes); +void iov_iter_revert(struct iov_iter *i, size_t bytes); int iov_iter_fault_in_readable(struct iov_iter *i, size_t bytes); size_t iov_iter_single_seg_count(const struct iov_iter *i); size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes, diff --git a/lib/iov_iter.c b/lib/iov_iter.c index e68604ae3ced..60abc44385b7 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -786,6 +786,68 @@ void iov_iter_advance(struct iov_iter *i, size_t size) } EXPORT_SYMBOL(iov_iter_advance); +void iov_iter_revert(struct iov_iter *i, size_t unroll) +{ + if (!unroll) + return; + i->count += unroll; + if (unlikely(i->type & ITER_PIPE)) { + struct pipe_inode_info *pipe = i->pipe; + int idx = i->idx; + size_t off = i->iov_offset; + while (1) { + size_t n = off - pipe->bufs[idx].offset; + if (unroll < n) { + off -= (n - unroll); + break; + } + unroll -= n; + if (!unroll && idx == i->start_idx) { + off = 0; + break; + } + if (!idx--) + idx = pipe->buffers - 1; + off = pipe->bufs[idx].offset + pipe->bufs[idx].len; + } + i->iov_offset = off; + i->idx = idx; + pipe_truncate(i); + return; + } + if (unroll <= i->iov_offset) { + i->iov_offset -= unroll; + return; + } + unroll -= i->iov_offset; + if (i->type & ITER_BVEC) { + const struct bio_vec *bvec = i->bvec; + while (1) { + size_t n = (--bvec)->bv_len; + i->nr_segs++; + if (unroll <= n) { + i->bvec = bvec; + i->iov_offset = n - unroll; + return; + } + unroll -= n; + } + } else { /* same logics for iovec and kvec */ + const struct iovec *iov = i->iov; + while (1) { + size_t n = (--iov)->iov_len; + i->nr_segs++; + if (unroll <= n) { + i->iov = iov; + i->iov_offset = n - unroll; + return; + } + unroll -= n; + } + } +} +EXPORT_SYMBOL(iov_iter_revert); + /* * Return the count of just the current iov_iter segment. */ @@ -839,6 +901,7 @@ void iov_iter_pipe(struct iov_iter *i, int direction, i->idx = (pipe->curbuf + pipe->nrbufs) & (pipe->buffers - 1); i->iov_offset = 0; i->count = count; + i->start_idx = i->idx; } EXPORT_SYMBOL(iov_iter_pipe); |