[PATCH 22/26] netfs, cachefiles: Implement helpers for new write code

David Howells
2024-03-28T16:38:48Z

Implement the helpers for the new write code in cachefiles. There's now an
optional ->prepare_write() that allows the filesystem to set the parameters
for the next write, such as maximum size and maximum segment count, and an
->issue_write() that is called to initiate an (asynchronous) write
operation.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Jeff Layton <jlayton@kernel.org>
cc: netfs@lists.linux.dev
cc: linux-erofs@lists.ozlabs.org
cc: linux-fsdevel@vger.kernel.org
---
fs/cachefiles/io.c | 73 ++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 73 insertions(+)

diff --git a/fs/cachefiles/io.c b/fs/cachefiles/io.c
index 5ba5c7814fe4..437b24b0fd1c 100644
--- a/fs/cachefiles/io.c
+++ b/fs/cachefiles/io.c
@@ -622,6 +622,77 @@ static int cachefiles_prepare_write(struct netfs_cache_resources *cres,
return ret;
}

+static void cachefiles_prepare_write_subreq(struct netfs_io_subrequest *subreq)
+{
+ struct netfs_io_request *wreq = subreq->rreq;
+ struct netfs_cache_resources *cres = &wreq->cache_resources;
+
+ _enter("W=%x[%x] %llx", wreq->debug_id, subreq->debug_index, subreq->start);
+
+ subreq->max_len = ULONG_MAX;
+ subreq->max_nr_segs = BIO_MAX_VECS;
+
+ if (!cachefiles_cres_file(cres)) {
+ if (!fscache_wait_for_operation(cres, FSCACHE_WANT_WRITE))
+ return netfs_prepare_write_failed(subreq);
+ if (!cachefiles_cres_file(cres))
+ return netfs_prepare_write_failed(subreq);
+ }
+}
+
+static void cachefiles_issue_write(struct netfs_io_subrequest *subreq)
+{
+ struct netfs_io_request *wreq = subreq->rreq;
+ struct netfs_cache_resources *cres = &wreq->cache_resources;
+ struct cachefiles_object *object = cachefiles_cres_object(cres);
+ struct cachefiles_cache *cache = object->volume->cache;
+ const struct cred *saved_cred;
+ size_t off, pre, post, len = subreq->len;
+ loff_t start = subreq->start;
+ int ret;
+
+ _enter("W=%x[%x] %llx-%llx",
+ wreq->debug_id, subreq->debug_index, start, start + len - 1);
+
+ /* We need to start on the cache granularity boundary */
+ off = start & (CACHEFILES_DIO_BLOCK_SIZE - 1);
+ if (off) {
+ pre = CACHEFILES_DIO_BLOCK_SIZE - off;
+ if (pre >= len) {
+ netfs_write_subrequest_terminated(subreq, len, false);
+ return;
+ }
+ subreq->transferred += pre;
+ start += pre;
+ len -= pre;
+ iov_iter_advance(&subreq->io_iter, pre);
+ }
+
+ /* We also need to end on the cache granularity boundary */
+ post = len & (CACHEFILES_DIO_BLOCK_SIZE - 1);
+ if (post) {
+ len -= post;
+ if (len == 0) {
+ netfs_write_subrequest_terminated(subreq, post, false);
+ return;
+ }
+ iov_iter_truncate(&subreq->io_iter, len);
+ }
+
+ cachefiles_begin_secure(cache, &saved_cred);
+ ret = __cachefiles_prepare_write(object, cachefiles_cres_file(cres),
+ &start, &len, len, true);
+ cachefiles_end_secure(cache, saved_cred);
+ if (ret < 0) {
+ netfs_write_subrequest_terminated(subreq, ret, false);
+ return;
+ }
+
+ cachefiles_write(&subreq->rreq->cache_resources,
+ subreq->start, &subreq->io_iter,
+ netfs_write_subrequest_terminated, subreq);
+}
+
/*
* Clean up an operation.
*/
@@ -638,8 +709,10 @@ static const struct netfs_cache_ops cachefiles_netfs_cache_ops = {
.end_operation = cachefiles_end_operation,
.read = cachefiles_read,
.write = cachefiles_write,
+ .issue_write = cachefiles_issue_write,
.prepare_read = cachefiles_prepare_read,
.prepare_write = cachefiles_prepare_write,
+ .prepare_write_subreq = cachefiles_prepare_write_subreq,
.prepare_ondemand_read = cachefiles_prepare_ondemand_read,
.query_occupancy = cachefiles_query_occupancy,
};