Fix EIO caused by network timeouts on changing file size.

To avoid spurious oplock breaks from server, in the case
of inodes that we already have open, avoid doing path
based setting of file size if we can do it by handle.
This keeps our caching token (oplock) and avoids
timeouts when the local oplock break takes longer to flush
writebehind data than the SMB timeout for the SetPathInfo 
request would allow

fs/cifs/inode.c

@@ -628,12 +628,14 @@ void
 cifs_truncate_file(struct inode *inode)
 {				/* BB remove - may not need this function after all BB */
 	int xid;
-	int rc = 0;
+	int rc = -EIO;
+	int found = FALSE;
 	struct cifsFileInfo *open_file = NULL;
 	struct cifs_sb_info *cifs_sb;
 	struct cifsTconInfo *pTcon;
 	struct cifsInodeInfo *cifsInode;
 	struct dentry *dirent;
+	struct list_head * tmp;
 	char *full_path = NULL;   
 
 	xid = GetXid();
@@ -641,6 +643,36 @@ cifs_truncate_file(struct inode *inode)
 	cifs_sb = CIFS_SB(inode->i_sb);
 	pTcon = cifs_sb->tcon;
 
+	/* To avoid spurious oplock breaks from server, in the case
+		of inodes that we already have open, avoid doing path
+		based setting of file size if we can do it by handle.
+		This keeps our caching token (oplock) and avoids
+		timeouts when the local oplock break takes longer to flush
+		writebehind data than the SMB timeout for the SetPathInfo 
+		request would allow */
+	read_lock(&GlobalSMBSeslock); 
+	cifsInode = CIFS_I(inode);
+	list_for_each(tmp, &cifsInode->openFileList) {            
+		open_file = list_entry(tmp,struct cifsFileInfo, flist);
+		/* We check if file is open for writing first */
+		if((open_file->pfile) && 
+		   ((open_file->pfile->f_flags & O_RDWR) || 
+			(open_file->pfile->f_flags & O_WRONLY))) {
+			read_unlock(&GlobalSMBSeslock);
+			found = TRUE;
+			rc = CIFSSMBSetFileSize(xid, pTcon, inode->i_size,
+			   open_file->netfid,open_file->pid,FALSE);
+			if(rc == 0) {
+				FreeXid(xid);
+				return;
+			}
+			break;  /* now that we found one valid file handle no
+				sense continuing to loop trying others */
+		}
+	}
+	if(found == FALSE)
+		read_unlock(&GlobalSMBSeslock);
+
 	if (list_empty(&inode->i_dentry)) {
 		cERROR(1,
 		       ("Can not get pathname from empty dentry in inode 0x%p ",
@@ -648,24 +680,13 @@ cifs_truncate_file(struct inode *inode)
 		FreeXid(xid);
 		return;
 	}
+
 	dirent = list_entry(inode->i_dentry.next, struct dentry, d_alias);
 	if (dirent) {
 		full_path = build_path_from_dentry(dirent);
 		rc = CIFSSMBSetEOF(xid, pTcon, full_path, inode->i_size,FALSE,
 				   cifs_sb->local_nls);
 		cFYI(1,(" SetEOF (truncate) rc = %d",rc));
-		if(rc == -ETXTBSY) {        
-			cifsInode = CIFS_I(inode);
-			if(!list_empty(&(cifsInode->openFileList))) {            
-				open_file = list_entry(cifsInode->openFileList.next,
-					struct cifsFileInfo, flist);           
-            /* We could check if file is open for writing first */
-				 rc = CIFSSMBSetFileSize(xid, pTcon, inode->i_size,
-					open_file->netfid,open_file->pid,FALSE);
-			} else {
-				  cFYI(1,(" No open files to get file handle from"));
-			}
-		}
 		if (!rc)
 			CIFSSMBSetEOF(xid,pTcon,full_path,inode->i_size,TRUE,cifs_sb->local_nls);
            /* allocation size setting seems optional so ignore return code */
@@ -706,6 +727,7 @@ cifs_setattr(struct dentry *direntry, struct iattr *attrs)
 	struct cifsTconInfo *pTcon;
 	char *full_path = NULL;
 	int rc = -EACCES;
+	int found = FALSE;
 	struct cifsFileInfo *open_file = NULL;
 	FILE_BASIC_INFO time_buf;
 	int set_time = FALSE;
@@ -713,6 +735,7 @@ cifs_setattr(struct dentry *direntry, struct iattr *attrs)
 	__u64 uid = 0xFFFFFFFFFFFFFFFFULL;
 	__u64 gid = 0xFFFFFFFFFFFFFFFFULL;
 	struct cifsInodeInfo *cifsInode;
+	struct list_head * tmp;
 
 	xid = GetXid();
 
@@ -730,28 +753,45 @@ cifs_setattr(struct dentry *direntry, struct iattr *attrs)
 	cFYI(1, (" Changing attributes 0x%x", attrs->ia_valid));
 
 	if (attrs->ia_valid & ATTR_SIZE) {
-		rc = CIFSSMBSetEOF(xid, pTcon, full_path, attrs->ia_size,FALSE,
-				   cifs_sb->local_nls);
-		cFYI(1,(" SetEOF (setattrs) rc = %d",rc));
-
-		if(rc == -ETXTBSY) {
-			if(!list_empty(&(cifsInode->openFileList))) {            
-				open_file = list_entry(cifsInode->openFileList.next, 
-					   struct cifsFileInfo, flist);           
-    /* We could check if file is open for writing first */
+		read_lock(&GlobalSMBSeslock); 
+		/* To avoid spurious oplock breaks from server, in the case
+			of inodes that we already have open, avoid doing path
+			based setting of file size if we can do it by handle.
+			This keeps our caching token (oplock) and avoids
+			timeouts when the local oplock break takes longer to flush
+			writebehind data than the SMB timeout for the SetPathInfo 
+			request would allow */
+		list_for_each(tmp, &cifsInode->openFileList) {            
+			open_file = list_entry(tmp,struct cifsFileInfo, flist);
+			/* We check if file is open for writing first */
+			if((open_file->pfile) && 
+				((open_file->pfile->f_flags & O_RDWR) || 
+				 (open_file->pfile->f_flags & O_WRONLY))) {
+				read_unlock(&GlobalSMBSeslock);
+				found = TRUE;
 				rc = CIFSSMBSetFileSize(xid, pTcon, attrs->ia_size,
-					   open_file->netfid,open_file->pid,FALSE);           
-			} else {
-				cFYI(1,(" No open files to get file handle from"));
+					   open_file->netfid,open_file->pid,FALSE);
+				cFYI(1,("SetFileSize by handle (setattrs) rc = %d",rc));
+				break;  /* now that we found one valid file handle no
+						sense continuing to loop trying others */
 			}
 		}
+		if(found == FALSE)
+			read_unlock(&GlobalSMBSeslock);
+
+		if(rc != 0) {
+			rc = CIFSSMBSetEOF(xid, pTcon, full_path, attrs->ia_size,FALSE,
+				   cifs_sb->local_nls);
+			cFYI(1,(" SetEOF by path (setattrs) rc = %d",rc));
+		}
+
         /*  For Allocation Size - do not need to call the following
             it did not hurt if it fails but why bother */
 	/*	CIFSSMBSetEOF(xid, pTcon, full_path, attrs->ia_size, TRUE, cifs_sb->local_nls);*/
+
 		if (rc == 0) {
 			rc = vmtruncate(direntry->d_inode, attrs->ia_size);
 			cifs_trunc_page(direntry->d_inode->i_mapping, direntry->d_inode->i_size); 
-
 /*          cFYI(1,("truncate_page to 0x%lx \n",direntry->d_inode->i_size)); */
 		}
 	}
@@ -817,6 +857,8 @@ cifs_setattr(struct dentry *direntry, struct iattr *attrs)
 		/* BB what if setting one attribute fails  
 			(such as size) but time setting works */
 		time_buf.CreationTime = 0;	/* do not change */
+		/* In the future we should experiment - try setting timestamps
+			 via Handle (SetFileInfo) instead of by path */
 		rc = CIFSSMBSetTimes(xid, pTcon, full_path, &time_buf,
 				cifs_sb->local_nls);
 	}