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Message-ID: <20250321161407.3333724-2-dhowells@redhat.com>
Date: Fri, 21 Mar 2025 16:14:01 +0000
From: David Howells <dhowells@...hat.com>
To: Leon Romanovsky <leonro@...dia.com>
Cc: David Howells <dhowells@...hat.com>,
Christian Brauner <christian@...uner.io>,
Matthew Wilcox <willy@...radead.org>,
Chuck Lever <chuck.lever@...cle.com>,
Steve French <smfrench@...il.com>,
Ilya Dryomov <idryomov@...il.com>,
netfs@...ts.linux.dev,
linux-fsdevel@...r.kernel.org,
linux-block@...r.kernel.org,
linux-mm@...ck.org,
linux-kernel@...r.kernel.org
Subject: [RFC PATCH 1/4] iov_iter: Move ITER_DISCARD and ITER_XARRAY iteration out-of-line
Move ITER_DISCARD and ITER_XARRAY iteration out-of-line in preparation of
adding other iteration types which will also be out-of-line.
Signed-off-by: David Howells <dhowells@...hat.com>
---
include/linux/iov_iter.h | 77 +++-----------------------------------
lib/iov_iter.c | 81 ++++++++++++++++++++++++++++++++++++++++
2 files changed, 86 insertions(+), 72 deletions(-)
diff --git a/include/linux/iov_iter.h b/include/linux/iov_iter.h
index c4aa58032faf..0c47933df517 100644
--- a/include/linux/iov_iter.h
+++ b/include/linux/iov_iter.h
@@ -17,6 +17,9 @@ typedef size_t (*iov_step_f)(void *iter_base, size_t progress, size_t len,
typedef size_t (*iov_ustep_f)(void __user *iter_base, size_t progress, size_t len,
void *priv, void *priv2);
+size_t __iterate_and_advance2(struct iov_iter *iter, size_t len, void *priv,
+ void *priv2, iov_ustep_f ustep, iov_step_f step);
+
/*
* Handle ITER_UBUF.
*/
@@ -195,72 +198,6 @@ size_t iterate_folioq(struct iov_iter *iter, size_t len, void *priv, void *priv2
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.
@@ -306,9 +243,7 @@ size_t iterate_and_advance2(struct iov_iter *iter, size_t len, void *priv,
return iterate_kvec(iter, len, priv, priv2, step);
if (iov_iter_is_folioq(iter))
return iterate_folioq(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);
+ return __iterate_and_advance2(iter, len, priv, priv2, ustep, step);
}
/**
@@ -370,9 +305,7 @@ size_t iterate_and_advance_kernel(struct iov_iter *iter, size_t len, void *priv,
return iterate_kvec(iter, len, priv, priv2, step);
if (iov_iter_is_folioq(iter))
return iterate_folioq(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);
+ return __iterate_and_advance2(iter, len, priv, priv2, NULL, step);
}
#endif /* _LINUX_IOV_ITER_H */
diff --git a/lib/iov_iter.c b/lib/iov_iter.c
index 65f550cb5081..33a8746e593e 100644
--- a/lib/iov_iter.c
+++ b/lib/iov_iter.c
@@ -1927,3 +1927,84 @@ ssize_t iov_iter_extract_pages(struct iov_iter *i,
return -EFAULT;
}
EXPORT_SYMBOL_GPL(iov_iter_extract_pages);
+
+/*
+ * 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;
+}
+
+/*
+ * Out of line iteration for iterator types that don't need such fast handling.
+ */
+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 (iov_iter_is_discard(iter))
+ return iterate_discard(iter, len, priv, priv2, step);
+ if (iov_iter_is_xarray(iter))
+ return iterate_xarray(iter, len, priv, priv2, step);
+ WARN_ON(1);
+ return 0;
+}
+EXPORT_SYMBOL(__iterate_and_advance2);
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