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 40106b7..da22497 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -1629,6 +1629,35 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
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 @@
}
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 @@
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);
}