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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-18 18:50:03 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-05-18 18:50:03 +0000
commit01a69402cf9d38ff180345d55c2ee51c7e89fbc7 (patch)
treeb406c5242a088c4f59c6e4b719b783f43aca6ae9 /fs/netfs/iterator.c
parentAdding upstream version 6.7.12. (diff)
downloadlinux-d6208063787d081e93f32d9942baa7f9358b45f1.tar.xz
linux-d6208063787d081e93f32d9942baa7f9358b45f1.zip
Adding upstream version 6.8.9.upstream/6.8.9
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'fs/netfs/iterator.c')
-rw-r--r--fs/netfs/iterator.c97
1 files changed, 97 insertions, 0 deletions
diff --git a/fs/netfs/iterator.c b/fs/netfs/iterator.c
index 2ff07ba655..b781bbbf1d 100644
--- a/fs/netfs/iterator.c
+++ b/fs/netfs/iterator.c
@@ -101,3 +101,100 @@ ssize_t netfs_extract_user_iter(struct iov_iter *orig, size_t orig_len,
return npages;
}
EXPORT_SYMBOL_GPL(netfs_extract_user_iter);
+
+/*
+ * Select the span of a bvec iterator we're going to use. Limit it by both maximum
+ * size and maximum number of segments. Returns the size of the span in bytes.
+ */
+static size_t netfs_limit_bvec(const struct iov_iter *iter, size_t start_offset,
+ size_t max_size, size_t max_segs)
+{
+ const struct bio_vec *bvecs = iter->bvec;
+ unsigned int nbv = iter->nr_segs, ix = 0, nsegs = 0;
+ size_t len, span = 0, n = iter->count;
+ size_t skip = iter->iov_offset + start_offset;
+
+ if (WARN_ON(!iov_iter_is_bvec(iter)) ||
+ WARN_ON(start_offset > n) ||
+ n == 0)
+ return 0;
+
+ while (n && ix < nbv && skip) {
+ len = bvecs[ix].bv_len;
+ if (skip < len)
+ break;
+ skip -= len;
+ n -= len;
+ ix++;
+ }
+
+ while (n && ix < nbv) {
+ len = min3(n, bvecs[ix].bv_len - skip, max_size);
+ span += len;
+ nsegs++;
+ ix++;
+ if (span >= max_size || nsegs >= max_segs)
+ break;
+ skip = 0;
+ n -= len;
+ }
+
+ return min(span, max_size);
+}
+
+/*
+ * Select the span of an xarray iterator we're going to use. Limit it by both
+ * maximum size and maximum number of segments. It is assumed that segments
+ * can be larger than a page in size, provided they're physically contiguous.
+ * Returns the size of the span in bytes.
+ */
+static size_t netfs_limit_xarray(const struct iov_iter *iter, size_t start_offset,
+ size_t max_size, size_t max_segs)
+{
+ struct folio *folio;
+ unsigned int nsegs = 0;
+ loff_t pos = iter->xarray_start + iter->iov_offset;
+ pgoff_t index = pos / PAGE_SIZE;
+ size_t span = 0, n = iter->count;
+
+ XA_STATE(xas, iter->xarray, index);
+
+ if (WARN_ON(!iov_iter_is_xarray(iter)) ||
+ WARN_ON(start_offset > n) ||
+ n == 0)
+ return 0;
+ max_size = min(max_size, n - start_offset);
+
+ rcu_read_lock();
+ xas_for_each(&xas, folio, ULONG_MAX) {
+ size_t offset, flen, len;
+ if (xas_retry(&xas, folio))
+ continue;
+ if (WARN_ON(xa_is_value(folio)))
+ break;
+ if (WARN_ON(folio_test_hugetlb(folio)))
+ break;
+
+ flen = folio_size(folio);
+ offset = offset_in_folio(folio, pos);
+ len = min(max_size, flen - offset);
+ span += len;
+ nsegs++;
+ if (span >= max_size || nsegs >= max_segs)
+ break;
+ }
+
+ rcu_read_unlock();
+ return min(span, max_size);
+}
+
+size_t netfs_limit_iter(const struct iov_iter *iter, size_t start_offset,
+ size_t max_size, size_t max_segs)
+{
+ if (iov_iter_is_bvec(iter))
+ return netfs_limit_bvec(iter, start_offset, max_size, max_segs);
+ if (iov_iter_is_xarray(iter))
+ return netfs_limit_xarray(iter, start_offset, max_size, max_segs);
+ BUG();
+}
+EXPORT_SYMBOL(netfs_limit_iter);