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ext4: Remove 65000 subdirectory limit
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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>
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Andreas Dilger authored and Theodore Ts'o committed Jul 18, 2007
1 parent 6dd4ee7 commit f8628a1
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Showing 2 changed files with 49 additions and 15 deletions.
60 changes: 46 additions & 14 deletions fs/ext4/namei.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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)
{
Expand Down Expand Up @@ -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:
Expand All @@ -1748,7 +1777,7 @@ static int ext4_mkdir(struct inode * dir, struct dentry * dentry, int mode)
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;
Expand Down Expand Up @@ -1780,7 +1809,7 @@ static int ext4_mkdir(struct inode * dir, struct dentry * dentry, int mode)
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);
Expand Down Expand Up @@ -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);
Expand All @@ -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);

Expand Down Expand Up @@ -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);
Expand Down Expand Up @@ -2159,7 +2188,7 @@ static int ext4_symlink (struct inode * dir,
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;
Expand All @@ -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.
Expand All @@ -2204,7 +2234,7 @@ static int ext4_link (struct dentry * old_dentry,
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);
Expand Down Expand Up @@ -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);
Expand All @@ -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);
}
Expand Down
4 changes: 3 additions & 1 deletion include/linux/ext4_fs.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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
Expand Down Expand Up @@ -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
Expand All @@ -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)

Expand Down

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