ext4: Remove 65000 subdirectory limit

This patch adds support to ext4 for allowing more than 65000
subdirectories. Currently the maximum number of subdirectories is capped
at 32000.

If we exceed 65000 subdirectories in an htree directory it sets the
inode link count to 1 and no longer counts subdirectories.  The
directory link count is not actually used when determining if a
directory is empty, as that only counts subdirectories and not regular
files that might be in there. 

A EXT4_FEATURE_RO_COMPAT_DIR_NLINK flag has been added and it is set if
the subdir count for any directory crosses 65000. A later fsck will clear
EXT4_FEATURE_RO_COMPAT_DIR_NLINK if there are no longer any directory
with >65000 subdirs.

Signed-off-by: Andreas Dilger <adilger@clusterfs.com>
Signed-off-by: Kalpak Shah <kalpak@clusterfs.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 3 insertions, 1 deletions

diff --git a/include/linux/ext4_fs.h b/include/linux/ext4_fs.h
index 52dcc24dd986..cdee7aaa57aa 100644
--- a/include/linux/ext4_fs.h
+++ b/include/linux/ext4_fs.h
@@ -71,7 +71,7 @@
 /*
  * Maximal count of links to a file
  */
-#define EXT4_LINK_MAX           32000
+#define EXT4_LINK_MAX           65000
 
 /*
  * Macro-instructions used to manage several block sizes
@@ -692,6 +692,7 @@ static inline int ext4_valid_inum(struct super_block *sb, unsigned long ino)
 #define EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER     0x0001
 #define EXT4_FEATURE_RO_COMPAT_LARGE_FILE       0x0002
 #define EXT4_FEATURE_RO_COMPAT_BTREE_DIR        0x0004
+#define EXT4_FEATURE_RO_COMPAT_DIR_NLINK        0x0020
 #define EXT4_FEATURE_RO_COMPAT_EXTRA_ISIZE      0x0040
 
 #define EXT4_FEATURE_INCOMPAT_COMPRESSION       0x0001
@@ -710,6 +711,7 @@ static inline int ext4_valid_inum(struct super_block *sb, unsigned long ino)
                                          EXT4_FEATURE_INCOMPAT_64BIT)
 #define EXT4_FEATURE_RO_COMPAT_SUPP     (EXT4_FEATURE_RO_COMPAT_SPARSE_SUPER| \
                                          EXT4_FEATURE_RO_COMPAT_LARGE_FILE| \
+                                         EXT4_FEATURE_RO_COMPAT_DIR_NLINK | \
                                          EXT4_FEATURE_RO_COMPAT_EXTRA_ISIZE | \
                                          EXT4_FEATURE_RO_COMPAT_BTREE_DIR)