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/* SPDX-License-Identifier: GPL-2.0-or-later */
/* I/O iterator iteration building functions.
*
* Copyright (C) 2023 Red Hat, Inc. All Rights Reserved.
* Written by David Howells ([email protected])
*/
#ifndef _LINUX_IOV_ITER_H
#define _LINUX_IOV_ITER_H
#include <linux/uio.h>
#include <linux/bvec.h>
typedef size_t (*iov_step_f)(void *iter_base, size_t progress, size_t len,
void *priv, void *priv2);
typedef size_t (*iov_ustep_f)(void __user *iter_base, size_t progress, size_t len,
void *priv, void *priv2);
/*
* Handle ITER_UBUF.
*/
static __always_inline
size_t iterate_ubuf(struct iov_iter *iter, size_t len, void *priv, void *priv2,
iov_ustep_f step)
{
void __user *base = iter->ubuf;
size_t progress = 0, remain;
remain = step(base + iter->iov_offset, 0, len, priv, priv2);
progress = len - remain;
iter->iov_offset += progress;
iter->count -= progress;
return progress;
}
/*
* Handle ITER_IOVEC.
*/
static __always_inline
size_t iterate_iovec(struct iov_iter *iter, size_t len, void *priv, void *priv2,
iov_ustep_f step)
{
const struct iovec *p = iter->__iov;
size_t progress = 0, skip = iter->iov_offset;
do {
size_t remain, consumed;
size_t part = min(len, p->iov_len - skip);
if (likely(part)) {
remain = step(p->iov_base + skip, progress, part, priv, priv2);
consumed = part - remain;
progress += consumed;
skip += consumed;
len -= consumed;
if (skip < p->iov_len)
break;
}
p++;
skip = 0;
} while (len);
iter->nr_segs -= p - iter->__iov;
iter->__iov = p;
iter->iov_offset = skip;
iter->count -= progress;
return progress;
}
/*
* Handle ITER_KVEC.
*/
static __always_inline
size_t iterate_kvec(struct iov_iter *iter, size_t len, void *priv, void *priv2,
iov_step_f step)
{
const struct kvec *p = iter->kvec;
size_t progress = 0, skip = iter->iov_offset;
do {
size_t remain, consumed;
size_t part = min(len, p->iov_len - skip);
if (likely(part)) {
remain = step(p->iov_base + skip, progress, part, priv, priv2);
consumed = part - remain;
progress += consumed;
skip += consumed;
len -= consumed;
if (skip < p->iov_len)
break;
}
p++;
skip = 0;
} while (len);
iter->nr_segs -= p - iter->kvec;
iter->kvec = p;
iter->iov_offset = skip;
iter->count -= progress;
return progress;
}
/*
* Handle ITER_BVEC.
*/
static __always_inline
size_t iterate_bvec(struct iov_iter *iter, size_t len, void *priv, void *priv2,
iov_step_f step)
{
const struct bio_vec *p = iter->bvec;
size_t progress = 0, skip = iter->iov_offset;
do {
size_t remain, consumed;
size_t offset = p->bv_offset + skip, part;
void *kaddr = kmap_local_page(p->bv_page + offset / PAGE_SIZE);
part = min3(len,
(size_t)(p->bv_len - skip),
(size_t)(PAGE_SIZE - offset % PAGE_SIZE));
remain = step(kaddr + offset % PAGE_SIZE, progress, part, priv, priv2);
kunmap_local(kaddr);
consumed = part - remain;
len -= consumed;
progress += consumed;
skip += consumed;
if (skip >= p->bv_len) {
skip = 0;
p++;
}
if (remain)
break;
} while (len);
iter->nr_segs -= p - iter->bvec;
iter->bvec = p;
iter->iov_offset = skip;
iter->count -= progress;
return progress;
}
/*
* Handle ITER_XARRAY.
*/
static __always_inline
size_t iterate_xarray(struct iov_iter *iter, size_t len, void *priv, void *priv2,
iov_step_f step)
{
struct folio *folio;
size_t progress = 0;
loff_t start = iter->xarray_start + iter->iov_offset;
pgoff_t index = start / PAGE_SIZE;
XA_STATE(xas, iter->xarray, index);
rcu_read_lock();
xas_for_each(&xas, folio, ULONG_MAX) {
size_t remain, consumed, offset, part, flen;
if (xas_retry(&xas, folio))
continue;
if (WARN_ON(xa_is_value(folio)))
break;
if (WARN_ON(folio_test_hugetlb(folio)))
break;
offset = offset_in_folio(folio, start + progress);
flen = min(folio_size(folio) - offset, len);
while (flen) {
void *base = kmap_local_folio(folio, offset);
part = min_t(size_t, flen,
PAGE_SIZE - offset_in_page(offset));
remain = step(base, progress, part, priv, priv2);
kunmap_local(base);
consumed = part - remain;
progress += consumed;
len -= consumed;
if (remain || len == 0)
goto out;
flen -= consumed;
offset += consumed;
}
}
out:
rcu_read_unlock();
iter->iov_offset += progress;
iter->count -= progress;
return progress;
}
/*
* Handle ITER_DISCARD.
*/
static __always_inline
size_t iterate_discard(struct iov_iter *iter, size_t len, void *priv, void *priv2,
iov_step_f step)
{
size_t progress = len;
iter->count -= progress;
return progress;
}
/**
* iterate_and_advance2 - Iterate over an iterator
* @iter: The iterator to iterate over.
* @len: The amount to iterate over.
* @priv: Data for the step functions.
* @priv2: More data for the step functions.
* @ustep: Function for UBUF/IOVEC iterators; given __user addresses.
* @step: Function for other iterators; given kernel addresses.
*
* Iterate over the next part of an iterator, up to the specified length. The
* buffer is presented in segments, which for kernel iteration are broken up by
* physical pages and mapped, with the mapped address being presented.
*
* Two step functions, @step and @ustep, must be provided, one for handling
* mapped kernel addresses and the other is given user addresses which have the
* potential to fault since no pinning is performed.
*
* The step functions are passed the address and length of the segment, @priv,
* @priv2 and the amount of data so far iterated over (which can, for example,
* be added to @priv to point to the right part of a second buffer). The step
* functions should return the amount of the segment they didn't process (ie. 0
* indicates complete processsing).
*
* This function returns the amount of data processed (ie. 0 means nothing was
* processed and the value of @len means processes to completion).
*/
static __always_inline
size_t iterate_and_advance2(struct iov_iter *iter, size_t len, void *priv,
void *priv2, iov_ustep_f ustep, iov_step_f step)
{
if (unlikely(iter->count < len))
len = iter->count;
if (unlikely(!len))
return 0;
if (likely(iter_is_ubuf(iter)))
return iterate_ubuf(iter, len, priv, priv2, ustep);
if (likely(iter_is_iovec(iter)))
return iterate_iovec(iter, len, priv, priv2, ustep);
if (iov_iter_is_bvec(iter))
return iterate_bvec(iter, len, priv, priv2, step);
if (iov_iter_is_kvec(iter))
return iterate_kvec(iter, len, priv, priv2, step);
if (iov_iter_is_xarray(iter))
return iterate_xarray(iter, len, priv, priv2, step);
return iterate_discard(iter, len, priv, priv2, step);
}
/**
* iterate_and_advance - Iterate over an iterator
* @iter: The iterator to iterate over.
* @len: The amount to iterate over.
* @priv: Data for the step functions.
* @ustep: Function for UBUF/IOVEC iterators; given __user addresses.
* @step: Function for other iterators; given kernel addresses.
*
* As iterate_and_advance2(), but priv2 is always NULL.
*/
static __always_inline
size_t iterate_and_advance(struct iov_iter *iter, size_t len, void *priv,
iov_ustep_f ustep, iov_step_f step)
{
return iterate_and_advance2(iter, len, priv, NULL, ustep, step);
}
#endif /* _LINUX_IOV_ITER_H */
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