diff options
author | David Howells <dhowells@redhat.com> | 2023-09-25 15:03:04 +0300 |
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committer | Christian Brauner <brauner@kernel.org> | 2023-09-25 15:30:28 +0300 |
commit | f1982740f5e77090bde41a9b84e257d69ec46598 (patch) | |
tree | 02934482ee795690c9a979e43f542f0252b4d963 /include/linux/iov_iter.h | |
parent | f1b4cb650b9a0eeba206d8f069fcdc532bfbcd74 (diff) | |
download | linux-f1982740f5e77090bde41a9b84e257d69ec46598.tar.xz |
iov_iter: Convert iterate*() to inline funcs
Convert the iov_iter iteration macros to inline functions to make the code
easier to follow.
The functions are marked __always_inline as we don't want to end up with
indirect calls in the code. This, however, leaves dealing with ->copy_mc
in an awkard situation since the step function (memcpy_from_iter_mc())
needs to test the flag in the iterator, but isn't passed the iterator.
This will be dealt with in a follow-up patch.
The variable names in the per-type iterator functions have been harmonised
as much as possible and made clearer as to the variable purpose.
The iterator functions are also moved to a header file so that other
operations that need to scan over an iterator can be added. For instance,
the rbd driver could use this to scan a buffer to see if it is all zeros
and libceph could use this to generate a crc.
Signed-off-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/3710261.1691764329@warthog.procyon.org.uk/ # v1
Link: https://lore.kernel.org/r/855.1692047347@warthog.procyon.org.uk/ # v2
Link: https://lore.kernel.org/r/20230816120741.534415-1-dhowells@redhat.com/ # v3
Link: https://lore.kernel.org/r/20230925120309.1731676-8-dhowells@redhat.com
cc: Alexander Viro <viro@zeniv.linux.org.uk>
cc: Jens Axboe <axboe@kernel.dk>
cc: Christoph Hellwig <hch@lst.de>
cc: Christian Brauner <christian@brauner.io>
cc: Matthew Wilcox <willy@infradead.org>
cc: Linus Torvalds <torvalds@linux-foundation.org>
cc: David Laight <David.Laight@ACULAB.COM>
cc: linux-block@vger.kernel.org
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
Diffstat (limited to 'include/linux/iov_iter.h')
-rw-r--r-- | include/linux/iov_iter.h | 274 |
1 files changed, 274 insertions, 0 deletions
diff --git a/include/linux/iov_iter.h b/include/linux/iov_iter.h new file mode 100644 index 000000000000..270454a6703d --- /dev/null +++ b/include/linux/iov_iter.h @@ -0,0 +1,274 @@ +/* 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 (dhowells@redhat.com) + */ + +#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 */ |