coda: add hinting support for partial file caching

This adds support for partial file caching in Coda.  Every read, write
and mmap informs the userspace cache manager about what part of a file
is about to be accessed so that the cache manager can ensure the
relevant parts are available before the operation is allowed to proceed.

When a read or write operation completes, this is also reported to allow
the cache manager to track when partially cached content can be
released.

If the cache manager does not support partial file caching, or when the
entire file has been fetched into the local cache, the cache manager may
return an EOPNOTSUPP error to indicate that intent upcalls are no longer
necessary until the file is closed.

[akpm@linux-foundation.org: little whitespace fixup]
Link: http://lkml.kernel.org/r/20190618181301.6960-1-jaharkes@cs.cmu.edu
Signed-off-by: Pedro Cuadra <pjcuadra@gmail.com>
Signed-off-by: Jan Harkes <jaharkes@cs.cmu.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 58 insertions, 12 deletions

diff --git a/fs/coda/upcall.c b/fs/coda/upcall.c
index 15c0e4fdb0e3..eb3b1898da46 100644
--- a/fs/coda/upcall.c
+++ b/fs/coda/upcall.c
@@ -569,6 +569,47 @@ int venus_statfs(struct dentry *dentry, struct kstatfs *sfs)
         return error;
 }
 
+int venus_access_intent(struct super_block *sb, struct CodaFid *fid,
+			bool *access_intent_supported,
+			size_t count, loff_t ppos, int type)
+{
+	union inputArgs *inp;
+	union outputArgs *outp;
+	int insize, outsize, error;
+	bool finalizer =
+		type == CODA_ACCESS_TYPE_READ_FINISH ||
+		type == CODA_ACCESS_TYPE_WRITE_FINISH;
+
+	if (!*access_intent_supported && !finalizer)
+		return 0;
+
+	insize = SIZE(access_intent);
+	UPARG(CODA_ACCESS_INTENT);
+
+	inp->coda_access_intent.VFid = *fid;
+	inp->coda_access_intent.count = count;
+	inp->coda_access_intent.pos = ppos;
+	inp->coda_access_intent.type = type;
+
+	error = coda_upcall(coda_vcp(sb), insize,
+			    finalizer ? NULL : &outsize, inp);
+
+	/*
+	 * we have to free the request buffer for synchronous upcalls
+	 * or when asynchronous upcalls fail, but not when asynchronous
+	 * upcalls succeed
+	 */
+	if (!finalizer || error)
+		kvfree(inp);
+
+	/* Chunked access is not supported or an old Coda client */
+	if (error == -EOPNOTSUPP) {
+		*access_intent_supported = false;
+		error = 0;
+	}
+	return error;
+}
+
 /*
  * coda_upcall and coda_downcall routines.
  */
@@ -598,10 +639,12 @@ static void coda_unblock_signals(sigset_t *old)
  * has seen them,
  * - CODA_CLOSE or CODA_RELEASE upcall  (to avoid reference count problems)
  * - CODA_STORE				(to avoid data loss)
+ * - CODA_ACCESS_INTENT                 (to avoid reference count problems)
  */
 #define CODA_INTERRUPTIBLE(r) (!coda_hard && \
 			       (((r)->uc_opcode != CODA_CLOSE && \
 				 (r)->uc_opcode != CODA_STORE && \
+				 (r)->uc_opcode != CODA_ACCESS_INTENT && \
 				 (r)->uc_opcode != CODA_RELEASE) || \
 				(r)->uc_flags & CODA_REQ_READ))
 
@@ -687,21 +730,25 @@ static int coda_upcall(struct venus_comm *vcp,
 		goto exit;
 	}
 
+	buffer->ih.unique = ++vcp->vc_seq;
+
 	req->uc_data = (void *)buffer;
-	req->uc_flags = 0;
+	req->uc_flags = outSize ? 0 : CODA_REQ_ASYNC;
 	req->uc_inSize = inSize;
-	req->uc_outSize = *outSize ? *outSize : inSize;
-	req->uc_opcode = ((union inputArgs *)buffer)->ih.opcode;
-	req->uc_unique = ++vcp->vc_seq;
+	req->uc_outSize = (outSize && *outSize) ? *outSize : inSize;
+	req->uc_opcode = buffer->ih.opcode;
+	req->uc_unique = buffer->ih.unique;
 	init_waitqueue_head(&req->uc_sleep);
 
-	/* Fill in the common input args. */
-	((union inputArgs *)buffer)->ih.unique = req->uc_unique;
-
 	/* Append msg to pending queue and poke Venus. */
 	list_add_tail(&req->uc_chain, &vcp->vc_pending);
-
 	wake_up_interruptible(&vcp->vc_waitq);
+
+	if (req->uc_flags & CODA_REQ_ASYNC) {
+		mutex_unlock(&vcp->vc_mutex);
+		return 0;
+	}
+
 	/* We can be interrupted while we wait for Venus to process
 	 * our request.  If the interrupt occurs before Venus has read
 	 * the request, we dequeue and return. If it occurs after the
@@ -743,20 +790,20 @@ static int coda_upcall(struct venus_comm *vcp,
 	sig_req = kmalloc(sizeof(struct upc_req), GFP_KERNEL);
 	if (!sig_req) goto exit;
 
-	sig_req->uc_data = kvzalloc(sizeof(struct coda_in_hdr), GFP_KERNEL);
-	if (!sig_req->uc_data) {
+	sig_inputArgs = kvzalloc(sizeof(struct coda_in_hdr), GFP_KERNEL);
+	if (!sig_inputArgs) {
 		kfree(sig_req);
 		goto exit;
 	}
 
 	error = -EINTR;
-	sig_inputArgs = (union inputArgs *)sig_req->uc_data;
 	sig_inputArgs->ih.opcode = CODA_SIGNAL;
 	sig_inputArgs->ih.unique = req->uc_unique;
 
 	sig_req->uc_flags = CODA_REQ_ASYNC;
 	sig_req->uc_opcode = sig_inputArgs->ih.opcode;
 	sig_req->uc_unique = sig_inputArgs->ih.unique;
+	sig_req->uc_data = (void *)sig_inputArgs;
 	sig_req->uc_inSize = sizeof(struct coda_in_hdr);
 	sig_req->uc_outSize = sizeof(struct coda_in_hdr);
 
@@ -911,4 +958,3 @@ unlock_out:
 	iput(inode);
 	return 0;
 }
-