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>

diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index 40106b7ea4b883d37eae792edafd0c77f682d115..da224974af7861efeab66cdd0de475e0679f9432 100644 (file)
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -1629,6 +1629,35 @@ static int ext4_delete_entry (handle_t *handle,
        return -ENOENT;
 }
 
+/*
+ * DIR_NLINK feature is set if 1) nlinks > EXT4_LINK_MAX or 2) nlinks == 2,
+ * since this indicates that nlinks count was previously 1.
+ */
+static void ext4_inc_count(handle_t *handle, struct inode *inode)
+{
+       inc_nlink(inode);
+       if (is_dx(inode) && inode->i_nlink > 1) {
+               /* limit is 16-bit i_links_count */
+               if (inode->i_nlink >= EXT4_LINK_MAX || inode->i_nlink == 2) {
+                       inode->i_nlink = 1;
+                       EXT4_SET_RO_COMPAT_FEATURE(inode->i_sb,
+                                             EXT4_FEATURE_RO_COMPAT_DIR_NLINK);
+               }
+       }
+}
+
+/*
+ * If a directory had nlink == 1, then we should let it be 1. This indicates
+ * directory has >EXT4_LINK_MAX subdirs.
+ */
+static void ext4_dec_count(handle_t *handle, struct inode *inode)
+{
+       drop_nlink(inode);
+       if (S_ISDIR(inode->i_mode) && inode->i_nlink == 0)
+               inc_nlink(inode);
+}
+
+
 static int ext4_add_nondir(handle_t *handle,
                struct dentry *dentry, struct inode *inode)
 {
@@ -1725,7 +1754,7 @@ static int ext4_mkdir(struct inode * dir, struct dentry * dentry, int mode)
        struct ext4_dir_entry_2 * de;
        int err, retries = 0;
 
-       if (dir->i_nlink >= EXT4_LINK_MAX)
+       if (EXT4_DIR_LINK_MAX(dir))
                return -EMLINK;
 
 retry:
@@ -1748,7 +1777,7 @@ retry:
        inode->i_size = EXT4_I(inode)->i_disksize = inode->i_sb->s_blocksize;
        dir_block = ext4_bread (handle, inode, 0, 1, &err);
        if (!dir_block) {
-               drop_nlink(inode); /* is this nlink == 0? */
+               ext4_dec_count(handle, inode); /* is this nlink == 0? */
                ext4_mark_inode_dirty(handle, inode);
                iput (inode);
                goto out_stop;
@@ -1780,7 +1809,7 @@ retry:
                iput (inode);
                goto out_stop;
        }
-       inc_nlink(dir);
+       ext4_inc_count(handle, dir);
        ext4_update_dx_flag(dir);
        ext4_mark_inode_dirty(handle, dir);
        d_instantiate(dentry, inode);
@@ -2045,9 +2074,9 @@ static int ext4_rmdir (struct inode * dir, struct dentry *dentry)
        retval = ext4_delete_entry(handle, dir, de, bh);
        if (retval)
                goto end_rmdir;
-       if (inode->i_nlink != 2)
+       if (!EXT4_DIR_LINK_EMPTY(inode))
                ext4_warning (inode->i_sb, "ext4_rmdir",
-                             "empty directory has nlink!=2 (%d)",
+                             "empty directory has too many links (%d)",
                              inode->i_nlink);
        inode->i_version++;
        clear_nlink(inode);
@@ -2058,7 +2087,7 @@ static int ext4_rmdir (struct inode * dir, struct dentry *dentry)
        ext4_orphan_add(handle, inode);
        inode->i_ctime = dir->i_ctime = dir->i_mtime = ext4_current_time(inode);
        ext4_mark_inode_dirty(handle, inode);
-       drop_nlink(dir);
+       ext4_dec_count(handle, dir);
        ext4_update_dx_flag(dir);
        ext4_mark_inode_dirty(handle, dir);
 
@@ -2109,7 +2138,7 @@ static int ext4_unlink(struct inode * dir, struct dentry *dentry)
        dir->i_ctime = dir->i_mtime = ext4_current_time(dir);
        ext4_update_dx_flag(dir);
        ext4_mark_inode_dirty(handle, dir);
-       drop_nlink(inode);
+       ext4_dec_count(handle, inode);
        if (!inode->i_nlink)
                ext4_orphan_add(handle, inode);
        inode->i_ctime = ext4_current_time(inode);
@@ -2159,7 +2188,7 @@ retry:
                err = __page_symlink(inode, symname, l,
                                mapping_gfp_mask(inode->i_mapping) & ~__GFP_FS);
                if (err) {
-                       drop_nlink(inode);
+                       ext4_dec_count(handle, inode);
                        ext4_mark_inode_dirty(handle, inode);
                        iput (inode);
                        goto out_stop;
@@ -2185,8 +2214,9 @@ static int ext4_link (struct dentry * old_dentry,
        struct inode *inode = old_dentry->d_inode;
        int err, retries = 0;
 
-       if (inode->i_nlink >= EXT4_LINK_MAX)
+       if (EXT4_DIR_LINK_MAX(inode))
                return -EMLINK;
+
        /*
         * Return -ENOENT if we've raced with unlink and i_nlink is 0.  Doing
         * otherwise has the potential to corrupt the orphan inode list.
@@ -2204,7 +2234,7 @@ retry:
                handle->h_sync = 1;
 
        inode->i_ctime = ext4_current_time(inode);
-       inc_nlink(inode);
+       ext4_inc_count(handle, inode);
        atomic_inc(&inode->i_count);
 
        err = ext4_add_nondir(handle, dentry, inode);
@@ -2337,7 +2367,7 @@ static int ext4_rename (struct inode * old_dir, struct dentry *old_dentry,
        }
 
        if (new_inode) {
-               drop_nlink(new_inode);
+               ext4_dec_count(handle, new_inode);
                new_inode->i_ctime = ext4_current_time(new_inode);
        }
        old_dir->i_ctime = old_dir->i_mtime = ext4_current_time(old_dir);
@@ -2348,11 +2378,13 @@ static int ext4_rename (struct inode * old_dir, struct dentry *old_dentry,
                PARENT_INO(dir_bh->b_data) = cpu_to_le32(new_dir->i_ino);
                BUFFER_TRACE(dir_bh, "call ext4_journal_dirty_metadata");
                ext4_journal_dirty_metadata(handle, dir_bh);
-               drop_nlink(old_dir);
+               ext4_dec_count(handle, old_dir);
                if (new_inode) {
-                       drop_nlink(new_inode);
+                       /* checked empty_dir above, can't have another parent,
+                        * ext3_dec_count() won't work for many-linked dirs */
+                       new_inode->i_nlink = 0;
                } else {
-                       inc_nlink(new_dir);
+                       ext4_inc_count(handle, new_dir);
                        ext4_update_dx_flag(new_dir);
                        ext4_mark_inode_dirty(handle, new_dir);
                }

diff --git a/include/linux/ext4_fs.h b/include/linux/ext4_fs.h
index 52dcc24dd9861e2e30301508283e9ec4913c92a3..cdee7aaa57aa60952281c54320f7a9bf0fa936fb 100644 (file)
--- 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)