[PATCH 2/6] CIFS: Make read call work with strict cache mode (try #4)

[Pavel Shilovsky <piastryyy-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

Add cifs_file_aio_read where we read from the cache if we have at least
Level II oplock - otherwise read from the server.

Signed-off-by: Pavel Shilovsky <piastryyy-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
---
 fs/cifs/cifsfs.c |   44 ++++++++++++++++++++++++++++++++++++++++++--
 1 files changed, 42 insertions(+), 2 deletions(-)

diff --git a/fs/cifs/cifsfs.c b/fs/cifs/cifsfs.c
index 9c37897..370acdc 100644
--- a/fs/cifs/cifsfs.c
+++ b/fs/cifs/cifsfs.c
@@ -568,6 +568,46 @@ cifs_do_mount(struct file_system_type *fs_type,
 	return dget(sb->s_root);
 }
 
+static ssize_t cifs_file_aio_read(struct kiocb *iocb, const struct iovec *iov,
+				  unsigned long nr_segs, loff_t pos)
+{
+	struct inode *inode;
+	struct cifs_sb_info *cifs_sb;
+	ssize_t read = 0, retval;
+	unsigned long i;
+
+	inode = iocb->ki_filp->f_path.dentry->d_inode;
+	cifs_sb = CIFS_SB(iocb->ki_filp->f_path.dentry->d_sb);
+
+	if ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_STRICT_IO) == 0 ||
+	    CIFS_I(inode)->clientCanCacheRead)
+		return generic_file_aio_read(iocb, iov, nr_segs, pos);
+
+	/*
+	 * In strict cache mode we need to read from the server all the time
+	 * if we don't have level II oplock because the server can delay mtime
+	 * change - so we can't make a decision about inode invalidating.
+	 * And we can also fail with pagereading if there are mandatory locks
+	 * on pages affected by this read but not on the region from pos to
+	 * pos+len-1.
+	 */
+
+	for (i = 0; i < nr_segs; i++) {
+		retval = cifs_user_read(iocb->ki_filp, iov[i].iov_base,
+					iov[i].iov_len, &pos);
+		if (retval < 0) {
+			read = read ? read : retval;
+			break;
+		}
+
+		read += retval;
+	}
+
+	iocb->ki_pos = pos;
+
+	return read;
+}
+
 static ssize_t cifs_file_aio_write(struct kiocb *iocb, const struct iovec *iov,
 				   unsigned long nr_segs, loff_t pos)
 {
@@ -690,7 +730,7 @@ const struct inode_operations cifs_symlink_inode_ops = {
 const struct file_operations cifs_file_ops = {
 	.read = do_sync_read,
 	.write = do_sync_write,
-	.aio_read = generic_file_aio_read,
+	.aio_read = cifs_file_aio_read,
 	.aio_write = cifs_file_aio_write,
 	.open = cifs_open,
 	.release = cifs_close,
@@ -727,7 +767,7 @@ const struct file_operations cifs_file_direct_ops = {
 const struct file_operations cifs_file_nobrl_ops = {
 	.read = do_sync_read,
 	.write = do_sync_write,
-	.aio_read = generic_file_aio_read,
+	.aio_read = cifs_file_aio_read,
 	.aio_write = cifs_file_aio_write,
 	.open = cifs_open,
 	.release = cifs_close,
-- 
1.7.3.2