[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>

fs/cifs/CHANGES

@@ -1,3 +1,9 @@
+Verison 1.48
+------------
+Fix mtime bouncing around from local idea of last write times to remote time.
+Fix hang (in i_size_read) when simultaneous size update of same remote file
+on smp system corrupts sequence number.
+ 
 Version 1.47
 ------------
 Fix oops in list_del during mount caused by unaligned string.

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 */

fs/cifs/inode.c

@@ -143,10 +143,10 @@ int cifs_get_inode_info_unix(struct inode **pinode,
 		inode->i_gid = le64_to_cpu(findData.Gid);
 		inode->i_nlink = le64_to_cpu(findData.Nlinks);
 
+		spin_lock(&inode->i_lock);
 		if (is_size_safe_to_change(cifsInfo, end_of_file)) {
 		/* can not safely change the file size here if the
 		   client is writing to it due to potential races */
-
 			i_size_write(inode, end_of_file);
 
 		/* blksize needs to be multiple of two. So safer to default to
@@ -162,6 +162,7 @@ int cifs_get_inode_info_unix(struct inode **pinode,
 		/* for this calculation */
 			inode->i_blocks = (512 - 1 + num_of_bytes) >> 9;
 		}
+		spin_unlock(&inode->i_lock);
 
 		if (num_of_bytes < end_of_file)
 			cFYI(1, ("allocation size less than end of file"));
@@ -496,6 +497,8 @@ int cifs_get_inode_info(struct inode **pinode,
 		/* BB add code here -
 		   validate if device or weird share or device type? */
 		}
+		
+		spin_lock(&inode->i_lock);
 		if (is_size_safe_to_change(cifsInfo, le64_to_cpu(pfindData->EndOfFile))) {
 			/* can not safely shrink the file size here if the
 			   client is writing to it due to potential races */
@@ -506,6 +509,7 @@ int cifs_get_inode_info(struct inode **pinode,
 			inode->i_blocks = (512 - 1 + le64_to_cpu(
 					   pfindData->AllocationSize)) >> 9;
 		}
+		spin_unlock(&inode->i_lock);
 
 		inode->i_nlink = le32_to_cpu(pfindData->NumberOfLinks);
 
@@ -834,8 +838,10 @@ int cifs_rmdir(struct inode *inode, struct dentry *direntry)
 
 	if (!rc) {
 		drop_nlink(inode);
+		spin_lock(&direntry->d_inode->i_lock);
 		i_size_write(direntry->d_inode,0);
 		clear_nlink(direntry->d_inode);
+		spin_unlock(&direntry->d_inode->i_lock);
 	}
 
 	cifsInode = CIFS_I(direntry->d_inode);
@@ -1128,6 +1134,46 @@ static int cifs_truncate_page(struct address_space *mapping, loff_t from)
 	return rc;
 }
 
+int cifs_vmtruncate(struct inode * inode, loff_t offset)
+{
+	struct address_space *mapping = inode->i_mapping;
+	unsigned long limit;
+
+	if (inode->i_size < offset)
+		goto do_expand;
+	/*
+	 * truncation of in-use swapfiles is disallowed - it would cause
+	 * subsequent swapout to scribble on the now-freed blocks.
+	 */
+	if (IS_SWAPFILE(inode))
+		goto out_busy;
+	spin_lock(&inode->i_lock);		
+	i_size_write(inode, offset);
+	spin_unlock(&inode->i_lock);
+	unmap_mapping_range(mapping, offset + PAGE_SIZE - 1, 0, 1);
+	truncate_inode_pages(mapping, offset);
+	goto out_truncate;
+
+do_expand:
+	limit = current->signal->rlim[RLIMIT_FSIZE].rlim_cur;
+	if (limit != RLIM_INFINITY && offset > limit)
+		goto out_sig;
+	if (offset > inode->i_sb->s_maxbytes)
+		goto out_big;
+	i_size_write(inode, offset);
+
+out_truncate:
+	if (inode->i_op && inode->i_op->truncate)
+		inode->i_op->truncate(inode);
+	return 0;
+out_sig:
+	send_sig(SIGXFSZ, current, 0);
+out_big:
+	return -EFBIG;
+out_busy:
+	return -ETXTBSY;
+}
+
 int cifs_setattr(struct dentry *direntry, struct iattr *attrs)
 {
 	int xid;
@@ -1244,7 +1290,7 @@ int cifs_setattr(struct dentry *direntry, struct iattr *attrs)
 		   */
 
 		if (rc == 0) {
-			rc = vmtruncate(direntry->d_inode, attrs->ia_size);
+			rc = cifs_vmtruncate(direntry->d_inode, attrs->ia_size);
 			cifs_truncate_page(direntry->d_inode->i_mapping,
 					   direntry->d_inode->i_size);
 		} else 

fs/cifs/readdir.c

@@ -3,7 +3,7 @@
  *
  *   Directory search handling
  * 
- *   Copyright (C) International Business Machines  Corp., 2004, 2005
+ *   Copyright (C) International Business Machines  Corp., 2004, 2007
  *   Author(s): Steve French (sfrench@us.ibm.com)
  *
  *   This library is free software; you can redistribute it and/or modify
@@ -226,6 +226,7 @@ static void fill_in_inode(struct inode *tmp_inode, int new_buf_type,
 		atomic_set(&cifsInfo->inUse, 1);
 	}
 
+	spin_lock(&tmp_inode->i_lock);
 	if (is_size_safe_to_change(cifsInfo, end_of_file)) {
 		/* can not safely change the file size here if the 
 		client is writing to it due to potential races */
@@ -235,6 +236,7 @@ static void fill_in_inode(struct inode *tmp_inode, int new_buf_type,
 	/* for this calculation, even though the reported blocksize is larger */
 		tmp_inode->i_blocks = (512 - 1 + allocation_size) >> 9;
 	}
+	spin_unlock(&tmp_inode->i_lock);
 
 	if (allocation_size < end_of_file)
 		cFYI(1, ("May be sparse file, allocation less than file size"));
@@ -355,6 +357,7 @@ static void unix_fill_in_inode(struct inode *tmp_inode,
 	tmp_inode->i_gid = le64_to_cpu(pfindData->Gid);
 	tmp_inode->i_nlink = le64_to_cpu(pfindData->Nlinks);
 
+	spin_lock(&tmp_inode->i_lock);
 	if (is_size_safe_to_change(cifsInfo, end_of_file)) {
 		/* can not safely change the file size here if the 
 		client is writing to it due to potential races */
@@ -364,6 +367,7 @@ static void unix_fill_in_inode(struct inode *tmp_inode,
 	/* for this calculation, not the real blocksize */
 		tmp_inode->i_blocks = (512 - 1 + num_of_bytes) >> 9;
 	}
+	spin_unlock(&tmp_inode->i_lock);
 
 	if (S_ISREG(tmp_inode->i_mode)) {
 		cFYI(1, ("File inode"));