fscache,cachefiles: add prepare_ondemand_read() callback

Add prepare_ondemand_read() callback dedicated for the on-demand read
scenario, so that callers from this scenario can be decoupled from
netfs_io_subrequest.

The original cachefiles_prepare_read() is now refactored to a generic
routine accepting a parameter list instead of netfs_io_subrequest.
There's no logic change, except that the debug id of subrequest and
request is removed from trace_cachefiles_prep_read().

Reviewed-by: Jeff Layton <jlayton@kernel.org>
Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Acked-by: David Howells <dhowells@redhat.com>
Link: https://lore.kernel.org/r/20221124034212.81892-2-jefflexu@linux.alibaba.com
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

1 files changed, 50 insertions, 27 deletions

diff --git a/fs/cachefiles/io.c b/fs/cachefiles/io.c
index 000a28f46e59..175a25fcade8 100644
--- a/fs/cachefiles/io.c
+++ b/fs/cachefiles/io.c
@@ -385,38 +385,35 @@ static int cachefiles_write(struct netfs_cache_resources *cres,
 				  term_func, term_func_priv);
 }
 
-/*
- * Prepare a read operation, shortening it to a cached/uncached
- * boundary as appropriate.
- */
-static enum netfs_io_source cachefiles_prepare_read(struct netfs_io_subrequest *subreq,
-						      loff_t i_size)
+static inline enum netfs_io_source
+cachefiles_do_prepare_read(struct netfs_cache_resources *cres,
+			   loff_t start, size_t *_len, loff_t i_size,
+			   unsigned long *_flags, ino_t netfs_ino)
 {
 	enum cachefiles_prepare_read_trace why;
-	struct netfs_io_request *rreq = subreq->rreq;
-	struct netfs_cache_resources *cres = &rreq->cache_resources;
-	struct cachefiles_object *object;
+	struct cachefiles_object *object = NULL;
 	struct cachefiles_cache *cache;
 	struct fscache_cookie *cookie = fscache_cres_cookie(cres);
 	const struct cred *saved_cred;
 	struct file *file = cachefiles_cres_file(cres);
 	enum netfs_io_source ret = NETFS_DOWNLOAD_FROM_SERVER;
+	size_t len = *_len;
 	loff_t off, to;
 	ino_t ino = file ? file_inode(file)->i_ino : 0;
 	int rc;
 
-	_enter("%zx @%llx/%llx", subreq->len, subreq->start, i_size);
+	_enter("%zx @%llx/%llx", len, start, i_size);
 
-	if (subreq->start >= i_size) {
+	if (start >= i_size) {
 		ret = NETFS_FILL_WITH_ZEROES;
 		why = cachefiles_trace_read_after_eof;
 		goto out_no_object;
 	}
 
 	if (test_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags)) {
-		__set_bit(NETFS_SREQ_COPY_TO_CACHE, &subreq->flags);
+		__set_bit(NETFS_SREQ_COPY_TO_CACHE, _flags);
 		why = cachefiles_trace_read_no_data;
-		if (!test_bit(NETFS_SREQ_ONDEMAND, &subreq->flags))
+		if (!test_bit(NETFS_SREQ_ONDEMAND, _flags))
 			goto out_no_object;
 	}
 
@@ -437,7 +434,7 @@ static enum netfs_io_source cachefiles_prepare_read(struct netfs_io_subrequest *
 retry:
 	off = cachefiles_inject_read_error();
 	if (off == 0)
-		off = vfs_llseek(file, subreq->start, SEEK_DATA);
+		off = vfs_llseek(file, start, SEEK_DATA);
 	if (off < 0 && off >= (loff_t)-MAX_ERRNO) {
 		if (off == (loff_t)-ENXIO) {
 			why = cachefiles_trace_read_seek_nxio;
@@ -449,21 +446,22 @@ retry:
 		goto out;
 	}
 
-	if (off >= subreq->start + subreq->len) {
+	if (off >= start + len) {
 		why = cachefiles_trace_read_found_hole;
 		goto download_and_store;
 	}
 
-	if (off > subreq->start) {
+	if (off > start) {
 		off = round_up(off, cache->bsize);
-		subreq->len = off - subreq->start;
+		len = off - start;
+		*_len = len;
 		why = cachefiles_trace_read_found_part;
 		goto download_and_store;
 	}
 
 	to = cachefiles_inject_read_error();
 	if (to == 0)
-		to = vfs_llseek(file, subreq->start, SEEK_HOLE);
+		to = vfs_llseek(file, start, SEEK_HOLE);
 	if (to < 0 && to >= (loff_t)-MAX_ERRNO) {
 		trace_cachefiles_io_error(object, file_inode(file), to,
 					  cachefiles_trace_seek_error);
@@ -471,12 +469,13 @@ retry:
 		goto out;
 	}
 
-	if (to < subreq->start + subreq->len) {
-		if (subreq->start + subreq->len >= i_size)
+	if (to < start + len) {
+		if (start + len >= i_size)
 			to = round_up(to, cache->bsize);
 		else
 			to = round_down(to, cache->bsize);
-		subreq->len = to - subreq->start;
+		len = to - start;
+		*_len = len;
 	}
 
 	why = cachefiles_trace_read_have_data;
@@ -484,12 +483,11 @@ retry:
 	goto out;
 
 download_and_store:
-	__set_bit(NETFS_SREQ_COPY_TO_CACHE, &subreq->flags);
-	if (test_bit(NETFS_SREQ_ONDEMAND, &subreq->flags)) {
-		rc = cachefiles_ondemand_read(object, subreq->start,
-					      subreq->len);
+	__set_bit(NETFS_SREQ_COPY_TO_CACHE, _flags);
+	if (test_bit(NETFS_SREQ_ONDEMAND, _flags)) {
+		rc = cachefiles_ondemand_read(object, start, len);
 		if (!rc) {
-			__clear_bit(NETFS_SREQ_ONDEMAND, &subreq->flags);
+			__clear_bit(NETFS_SREQ_ONDEMAND, _flags);
 			goto retry;
 		}
 		ret = NETFS_INVALID_READ;
@@ -497,11 +495,35 @@ download_and_store:
 out:
 	cachefiles_end_secure(cache, saved_cred);
 out_no_object:
-	trace_cachefiles_prep_read(subreq, ret, why, ino);
+	trace_cachefiles_prep_read(object, start, len, *_flags, ret, why, ino, netfs_ino);
 	return ret;
 }
 
 /*
+ * Prepare a read operation, shortening it to a cached/uncached
+ * boundary as appropriate.
+ */
+static enum netfs_io_source cachefiles_prepare_read(struct netfs_io_subrequest *subreq,
+						    loff_t i_size)
+{
+	return cachefiles_do_prepare_read(&subreq->rreq->cache_resources,
+					  subreq->start, &subreq->len, i_size,
+					  &subreq->flags, subreq->rreq->inode->i_ino);
+}
+
+/*
+ * Prepare an on-demand read operation, shortening it to a cached/uncached
+ * boundary as appropriate.
+ */
+static enum netfs_io_source
+cachefiles_prepare_ondemand_read(struct netfs_cache_resources *cres,
+				 loff_t start, size_t *_len, loff_t i_size,
+				 unsigned long *_flags, ino_t ino)
+{
+	return cachefiles_do_prepare_read(cres, start, _len, i_size, _flags, ino);
+}
+
+/*
  * Prepare for a write to occur.
  */
 int __cachefiles_prepare_write(struct cachefiles_object *object,
@@ -621,6 +643,7 @@ static const struct netfs_cache_ops cachefiles_netfs_cache_ops = {
 	.write			= cachefiles_write,
 	.prepare_read		= cachefiles_prepare_read,
 	.prepare_write		= cachefiles_prepare_write,
+	.prepare_ondemand_read	= cachefiles_prepare_ondemand_read,
 	.query_occupancy	= cachefiles_query_occupancy,
 };