ext4: Rename and document EXT4_EX_FILTER to EXT4_EX_QUERY_FILTER

Rename EXT4_EX_FILTER to EXT4_EX_QUERY_FILTER to better describe its
purpose as a filter mask used specifically in ext4_map_query_blocks().
Add a comment explaining that this macro is used to filter flags needed
when querying the on-disk extent tree.

We will later use EXT4_EX_QUERY_FILTER mask to add another
EXT4_GET_BLOCKS_QUERY needed to lookup in on-disk extent tree.

Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Link: https://patch.msgid.link/51f05d0ba286372eb8693af95bd4b10194b53141.1747677758.git.ritesh.list@gmail.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Author: riteshharjani

fs/ext4/ext4.h

@@ -757,7 +757,12 @@ enum {
 #define EXT4_EX_NOCACHE				0x40000000
 #define EXT4_EX_FORCE_CACHE			0x20000000
 #define EXT4_EX_NOFAIL				0x10000000
-#define EXT4_EX_FILTER				0x70000000
+/*
+ * ext4_map_query_blocks() uses this filter mask to filter the flags needed to
+ * pass while lookup/querying of on disk extent tree.
+ */
+#define EXT4_EX_QUERY_FILTER	(EXT4_EX_NOCACHE | EXT4_EX_FORCE_CACHE |\
+				 EXT4_EX_NOFAIL)
 
 /*
  * Flags used by ext4_free_blocks

fs/ext4/inode.c

@@ -546,7 +546,7 @@ static int ext4_map_query_blocks(handle_t *handle, struct inode *inode,
 	unsigned int orig_mlen = map->m_len;
 	unsigned int query_flags = flags & EXT4_GET_BLOCKS_QUERY_LAST_IN_LEAF;
 
-	flags &= EXT4_EX_FILTER;
+	flags &= EXT4_EX_QUERY_FILTER;
 	if (ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))
 		retval = ext4_ext_map_blocks(handle, inode, map,
 					     flags | query_flags);