CIFS: Fix write after setting a read lock for read oplock files

If we have a read oplock and set a read lock in it, we can't write to the
locked area - so, filemap_fdatawrite may fail with a no information for a
userspace application even if we request a write to non-locked area. Fix
this by populating the page cache without marking affected pages dirty
after a successful write directly to the server.

Also remove CONFIG_CIFS_SMB2 ifdefs because it's suitable for both CIFS
and SMB2 protocols.

Signed-off-by: Pavel Shilovsky <piastry@etersoft.ru>
Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Steve French <smfrench@gmail.com>

fs/cifs/cifsfs.c

@@ -229,6 +229,7 @@ cifs_alloc_inode(struct super_block *sb)
 	cifs_set_oplock_level(cifs_inode, 0);
 	cifs_inode->delete_pending = false;
 	cifs_inode->invalid_mapping = false;
+	cifs_inode->leave_pages_clean = false;
 	cifs_inode->vfs_inode.i_blkbits = 14;  /* 2**14 = CIFS_MAX_MSGSIZE */
 	cifs_inode->server_eof = 0;
 	cifs_inode->uniqueid = 0;

fs/cifs/cifsglob.h

@@ -1030,6 +1030,7 @@ struct cifsInodeInfo {
 	bool clientCanCacheAll;		/* read and writebehind oplock */
 	bool delete_pending;		/* DELETE_ON_CLOSE is set */
 	bool invalid_mapping;		/* pagecache is invalid */
+	bool leave_pages_clean;	/* protected by i_mutex, not set pages dirty */
 	unsigned long time;		/* jiffies of last update of inode */
 	u64  server_eof;		/* current file size on server -- protected by i_lock */
 	u64  uniqueid;			/* server inode number */

fs/cifs/file.c

@@ -2103,7 +2103,15 @@ static int cifs_write_end(struct file *file, struct address_space *mapping,
 	} else {
 		rc = copied;
 		pos += copied;
-		set_page_dirty(page);
+		/*
+		 * When we use strict cache mode and cifs_strict_writev was run
+		 * with level II oplock (indicated by leave_pages_clean field of
+		 * CIFS_I(inode)), we can leave pages clean - cifs_strict_writev
+		 * sent the data to the server itself.
+		 */
+		if (!CIFS_I(inode)->leave_pages_clean ||
+		    !(cifs_sb->mnt_cifs_flags & CIFS_MOUNT_STRICT_IO))
+			set_page_dirty(page);
 	}
 
 	if (rc > 0) {
@@ -2454,8 +2462,8 @@ ssize_t cifs_user_writev(struct kiocb *iocb, const struct iovec *iov,
 }
 
 static ssize_t
-cifs_writev(struct kiocb *iocb, const struct iovec *iov,
-	    unsigned long nr_segs, loff_t pos)
+cifs_pagecache_writev(struct kiocb *iocb, const struct iovec *iov,
+		      unsigned long nr_segs, loff_t pos, bool cache_ex)
 {
 	struct file *file = iocb->ki_filp;
 	struct cifsFileInfo *cfile = (struct cifsFileInfo *)file->private_data;
@@ -2477,8 +2485,12 @@ cifs_writev(struct kiocb *iocb, const struct iovec *iov,
 				     server->vals->exclusive_lock_type, NULL,
 				     CIFS_WRITE_OP)) {
 		mutex_lock(&inode->i_mutex);
+		if (!cache_ex)
+			cinode->leave_pages_clean = true;
 		rc = __generic_file_aio_write(iocb, iov, nr_segs,
-					       &iocb->ki_pos);
+					      &iocb->ki_pos);
+		if (!cache_ex)
+			cinode->leave_pages_clean = false;
 		mutex_unlock(&inode->i_mutex);
 	}
 
@@ -2505,42 +2517,62 @@ cifs_strict_writev(struct kiocb *iocb, const struct iovec *iov,
 	struct cifsFileInfo *cfile = (struct cifsFileInfo *)
 						iocb->ki_filp->private_data;
 	struct cifs_tcon *tcon = tlink_tcon(cfile->tlink);
-
-#ifdef CONFIG_CIFS_SMB2
+	ssize_t written, written2;
 	/*
-	 * If we have an oplock for read and want to write a data to the file
-	 * we need to store it in the page cache and then push it to the server
-	 * to be sure the next read will get a valid data.
+	 * We need to store clientCanCacheAll here to prevent race
+	 * conditions - this value can be changed during an execution
+	 * of generic_file_aio_write. For CIFS it can be changed from
+	 * true to false only, but for SMB2 it can be changed both from
+	 * true to false and vice versa. So, we can end up with a data
+	 * stored in the cache, not marked dirty and not sent to the
+	 * server if this value changes its state from false to true
+	 * after cifs_write_end.
 	 */
-	if (!cinode->clientCanCacheAll && cinode->clientCanCacheRead) {
-		ssize_t written;
-		int rc;
-
-		written = generic_file_aio_write(iocb, iov, nr_segs, pos);
-		rc = filemap_fdatawrite(inode->i_mapping);
-		if (rc)
-			return (ssize_t)rc;
+	bool cache_ex = cinode->clientCanCacheAll;
+	bool cache_read = cinode->clientCanCacheRead;
+	int rc;
+	loff_t saved_pos;
 
-		return written;
+	if (cache_ex) {
+		if (cap_unix(tcon->ses) &&
+		    ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NOPOSIXBRL) == 0) &&
+		    (CIFS_UNIX_FCNTL_CAP & le64_to_cpu(
+						tcon->fsUnixInfo.Capability)))
+			return generic_file_aio_write(iocb, iov, nr_segs, pos);
+		return cifs_pagecache_writev(iocb, iov, nr_segs, pos, cache_ex);
 	}
-#endif
 
 	/*
-	 * For non-oplocked files in strict cache mode we need to write the data
-	 * to the server exactly from the pos to pos+len-1 rather than flush all
-	 * affected pages because it may cause a error with mandatory locks on
-	 * these pages but not on the region from pos to ppos+len-1.
+	 * For files without exclusive oplock in strict cache mode we need to
+	 * write the data to the server exactly from the pos to pos+len-1 rather
+	 * than flush all affected pages because it may cause a error with
+	 * mandatory locks on these pages but not on the region from pos to
+	 * ppos+len-1.
 	 */
+	written = cifs_user_writev(iocb, iov, nr_segs, pos);
+	if (!cache_read || written <= 0)
+		return written;
 
-	if (!cinode->clientCanCacheAll)
-		return cifs_user_writev(iocb, iov, nr_segs, pos);
-
+	saved_pos = iocb->ki_pos;
+	iocb->ki_pos = pos;
+	/* we have a read oplock - need to store a data in the page cache */
 	if (cap_unix(tcon->ses) &&
-	    (CIFS_UNIX_FCNTL_CAP & le64_to_cpu(tcon->fsUnixInfo.Capability)) &&
-	    ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NOPOSIXBRL) == 0))
-		return generic_file_aio_write(iocb, iov, nr_segs, pos);
-
-	return cifs_writev(iocb, iov, nr_segs, pos);
+	    ((cifs_sb->mnt_cifs_flags & CIFS_MOUNT_NOPOSIXBRL) == 0) &&
+	    (CIFS_UNIX_FCNTL_CAP & le64_to_cpu(
+					tcon->fsUnixInfo.Capability)))
+		written2 = generic_file_aio_write(iocb, iov, nr_segs, pos);
+	else
+		written2 = cifs_pagecache_writev(iocb, iov, nr_segs, pos,
+						 cache_ex);
+	/* errors occured during writing - invalidate the page cache */
+	if (written2 < 0) {
+		rc = cifs_invalidate_mapping(inode);
+		if (rc)
+			written = (ssize_t)rc;
+		else
+			iocb->ki_pos = saved_pos;
+	}
+	return written;
 }
 
 static struct cifs_readdata *