netfs: Provide an iterator-reset function

Provide a function to reset the iterator on a subrequest.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Jeff Layton <jlayton@kernel.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
Link: https://lore.kernel.org/r/20240814203850.2240469-17-dhowells@redhat.com/
Signed-off-by: Christian Brauner <brauner@kernel.org>

diff --git a/fs/netfs/internal.h b/fs/netfs/internal.h
index e1149e05a5c8e6cdc939099f9d073dd63c24db9b..21a3c7d135853be0b53db7c8e779933ada2258c9 100644 (file)
--- a/fs/netfs/internal.h
+++ b/fs/netfs/internal.h
@@ -69,6 +69,7 @@ int netfs_buffer_append_folio(struct netfs_io_request *rreq, struct folio *folio
                              bool needs_put);
 struct folio_queue *netfs_delete_buffer_head(struct netfs_io_request *wreq);
 void netfs_clear_buffer(struct netfs_io_request *rreq);
+void netfs_reset_iter(struct netfs_io_subrequest *subreq);
 
 /*
  * objects.c
@@ -161,9 +162,6 @@ struct netfs_io_request *netfs_create_write_req(struct address_space *mapping,
 void netfs_reissue_write(struct netfs_io_stream *stream,
                         struct netfs_io_subrequest *subreq,
                         struct iov_iter *source);
-int netfs_advance_write(struct netfs_io_request *wreq,
-                       struct netfs_io_stream *stream,
-                       loff_t start, size_t len, bool to_eof);
 struct netfs_io_request *netfs_begin_writethrough(struct kiocb *iocb, size_t len);
 int netfs_advance_writethrough(struct netfs_io_request *wreq, struct writeback_control *wbc,
                               struct folio *folio, size_t copied, bool to_page_end,

diff --git a/fs/netfs/misc.c b/fs/netfs/misc.c
index 4cd2f84415c1bd83d075b4e121843ea5f2910be6..0ad0982ce0e207ecae4ce5a1d04c8dab9475464b 100644 (file)
--- a/fs/netfs/misc.c
+++ b/fs/netfs/misc.c
@@ -84,6 +84,24 @@ void netfs_clear_buffer(struct netfs_io_request *rreq)
        }
 }
 
+/*
+ * Reset the subrequest iterator to refer just to the region remaining to be
+ * read.  The iterator may or may not have been advanced by socket ops or
+ * extraction ops to an extent that may or may not match the amount actually
+ * read.
+ */
+void netfs_reset_iter(struct netfs_io_subrequest *subreq)
+{
+       struct iov_iter *io_iter = &subreq->io_iter;
+       size_t remain = subreq->len - subreq->transferred;
+
+       if (io_iter->count > remain)
+               iov_iter_advance(io_iter, io_iter->count - remain);
+       else if (io_iter->count < remain)
+               iov_iter_revert(io_iter, remain - io_iter->count);
+       iov_iter_truncate(&subreq->io_iter, remain);
+}
+
 /**
  * netfs_dirty_folio - Mark folio dirty and pin a cache object for writeback
  * @mapping: The mapping the folio belongs to.

diff --git a/fs/netfs/write_collect.c b/fs/netfs/write_collect.c
index 7a41e76c1ba9c0075552ba1c72b549b8509ac485..2a47af45faa0f90cdb16695f29b627b3ff20953f 100644 (file)
--- a/fs/netfs/write_collect.c
+++ b/fs/netfs/write_collect.c
@@ -226,9 +226,8 @@ static void netfs_retry_write_stream(struct netfs_io_request *wreq,
                /* Determine the set of buffers we're going to use.  Each
                 * subreq gets a subset of a single overall contiguous buffer.
                 */
+               netfs_reset_iter(from);
                source = from->io_iter;
-               iov_iter_revert(&source, subreq->len - source.count);
-               iov_iter_advance(&source, from->transferred);
                source.count = len;
 
                /* Work through the sublist. */

diff --git a/fs/netfs/write_issue.c b/fs/netfs/write_issue.c
index a75b62b202c563c5c6d361f3bde9104184159a5a..9ead075962f0d387cfc62653b9ec0d0ca5f3ffc1 100644 (file)
--- a/fs/netfs/write_issue.c
+++ b/fs/netfs/write_issue.c
@@ -261,9 +261,9 @@ static void netfs_issue_write(struct netfs_io_request *wreq,
  * we can avoid overrunning the credits obtained (cifs) and try to parallelise
  * content-crypto preparation with network writes.
  */
-int netfs_advance_write(struct netfs_io_request *wreq,
-                       struct netfs_io_stream *stream,
-                       loff_t start, size_t len, bool to_eof)
+static int netfs_advance_write(struct netfs_io_request *wreq,
+                              struct netfs_io_stream *stream,
+                              loff_t start, size_t len, bool to_eof)
 {
        struct netfs_io_subrequest *subreq = stream->construct;
        size_t part;