[CIFS] Fix locking problem around some cifs uses of i_size write

Could cause hangs on smp systems in i_size_read on a cifs inode
whose size has been previously simultaneously updated from
different processes.

Thanks to Brian Wang for some great testing/debugging on this
hard problem.

Fixes kernel bugzilla #7903

CC: Shirish Pargoankar <shirishp@us.ibm.com>
CC: Shaggy <shaggy@us.ibm.com>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 23 insertions, 20 deletions

diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index a1265c9bfec0..c07ff8317a8b 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -879,18 +879,19 @@ ssize_t cifs_user_write(struct file *file, const char __user *write_data,
 	cifs_stats_bytes_written(pTcon, total_written);
 
 	/* since the write may have blocked check these pointers again */
-	if (file->f_path.dentry) {
-		if (file->f_path.dentry->d_inode) {
-			struct inode *inode = file->f_path.dentry->d_inode;
-			inode->i_ctime = inode->i_mtime =
-				current_fs_time(inode->i_sb);
-			if (total_written > 0) {
-				if (*poffset > file->f_path.dentry->d_inode->i_size)
-					i_size_write(file->f_path.dentry->d_inode,
+	if ((file->f_path.dentry) && (file->f_path.dentry->d_inode)) {
+		struct inode *inode = file->f_path.dentry->d_inode;
+/* Do not update local mtime - server will set its actual value on write		
+ *		inode->i_ctime = inode->i_mtime = 
+ * 			current_fs_time(inode->i_sb);*/
+		if (total_written > 0) {
+			spin_lock(&inode->i_lock);
+			if (*poffset > file->f_path.dentry->d_inode->i_size)
+				i_size_write(file->f_path.dentry->d_inode,
 					*poffset);
-			}
-			mark_inode_dirty_sync(file->f_path.dentry->d_inode);
+			spin_unlock(&inode->i_lock);
 		}
+		mark_inode_dirty_sync(file->f_path.dentry->d_inode);	
 	}
 	FreeXid(xid);
 	return total_written;
@@ -1012,18 +1013,18 @@ static ssize_t cifs_write(struct file *file, const char *write_data,
 	cifs_stats_bytes_written(pTcon, total_written);
 
 	/* since the write may have blocked check these pointers again */
-	if (file->f_path.dentry) {
-		if (file->f_path.dentry->d_inode) {
+	if ((file->f_path.dentry) && (file->f_path.dentry->d_inode)) {
 /*BB We could make this contingent on superblock ATIME flag too */
-/*			file->f_path.dentry->d_inode->i_ctime =
-			file->f_path.dentry->d_inode->i_mtime = CURRENT_TIME;*/
-			if (total_written > 0) {
-				if (*poffset > file->f_path.dentry->d_inode->i_size)
-					i_size_write(file->f_path.dentry->d_inode,
-						     *poffset);
-			}
-			mark_inode_dirty_sync(file->f_path.dentry->d_inode);
+/*		file->f_path.dentry->d_inode->i_ctime =
+		file->f_path.dentry->d_inode->i_mtime = CURRENT_TIME;*/
+		if (total_written > 0) {
+			spin_lock(&file->f_path.dentry->d_inode->i_lock);
+			if (*poffset > file->f_path.dentry->d_inode->i_size)
+				i_size_write(file->f_path.dentry->d_inode,
+					     *poffset);
+			spin_unlock(&file->f_path.dentry->d_inode->i_lock);
 		}
+		mark_inode_dirty_sync(file->f_path.dentry->d_inode);
 	}
 	FreeXid(xid);
 	return total_written;
@@ -1400,6 +1401,7 @@ static int cifs_commit_write(struct file *file, struct page *page,
 	xid = GetXid();
 	cFYI(1, ("commit write for page %p up to position %lld for %d", 
 		 page, position, to));
+	spin_lock(&inode->i_lock);
 	if (position > inode->i_size) {
 		i_size_write(inode, position);
 		/* if (file->private_data == NULL) {
@@ -1429,6 +1431,7 @@ static int cifs_commit_write(struct file *file, struct page *page,
 			cFYI(1, (" SetEOF (commit write) rc = %d", rc));
 		} */
 	}
+	spin_unlock(&inode->i_lock);
 	if (!PageUptodate(page)) {
 		position =  ((loff_t)page->index << PAGE_CACHE_SHIFT) + offset;
 		/* can not rely on (or let) writepage write this data */