[JFFS2] Use ALLOC_DELETION priority for truncation to zero length

This is going to obsolete all previous nodes, so treat it as deletion.

Signed-off-by: David Woodhouse <dwmw2@infradead.org>

fs/jffs2/fs.c

@@ -36,6 +36,7 @@ int jffs2_do_setattr (struct inode *inode, struct iattr *iattr)
 	unsigned int ivalid;
 	uint32_t alloclen;
 	int ret;
+	int alloc_type = ALLOC_NORMAL;
 
 	D1(printk(KERN_DEBUG "jffs2_setattr(): ino #%lu\n", inode->i_ino));
 
@@ -115,14 +116,18 @@ int jffs2_do_setattr (struct inode *inode, struct iattr *iattr)
 		ri->compr = JFFS2_COMPR_ZERO;
 		ri->dsize = cpu_to_je32(iattr->ia_size - inode->i_size);
 		ri->offset = cpu_to_je32(inode->i_size);
+	} else if (ivalid & ATTR_SIZE && !iattr->ia_size) {
+		/* For truncate-to-zero, treat it as deletion because
+		   it'll always be obsoleting all previous nodes */
+		alloc_type = ALLOC_DELETION;
 	}
 	ri->node_crc = cpu_to_je32(crc32(0, ri, sizeof(*ri)-8));
 	if (mdatalen)
 		ri->data_crc = cpu_to_je32(crc32(0, mdata, mdatalen));
 	else
 		ri->data_crc = cpu_to_je32(0);
 
-	new_metadata = jffs2_write_dnode(c, f, ri, mdata, mdatalen, ALLOC_NORMAL);
+	new_metadata = jffs2_write_dnode(c, f, ri, mdata, mdatalen, alloc_type);
 	if (S_ISLNK(inode->i_mode))
 		kfree(mdata);