Re: [EXT4 set 7][PATCH 1/1]Remove 32000 subdirs limit.
- From: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
- Date: Tue, 10 Jul 2007 22:40:11 -0700
On Sun, 01 Jul 2007 03:38:18 -0400 Mingming Cao <cmm@xxxxxxxxxx> wrote:
From kalpak@xxxxxxxxxxxxx Thu May 17 17:21:08 2007Hi,
I have rebased this patch to 2.6.22-rc1 so that it can be added to the
ext4 patch queue. It has been tested by creating more than 65000 subdirs
and then deleting them and checking the nlinks. The e2fsprogs part of
this patch was sent earlier by me to linux-ext4 and doesn't need any
changes, so not submitting it again.
----------------------------------------------------------------------
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.
Would I be correct in assuming that a later fsck will clear
EXT4_FEATURE_RO_COMPAT_DIR_NLINK if there are no longer any >65000 subdir
directories?
If so, that is worth a mention in the changelog, perhaps?
Please remind us what is the behaviour of an RO_COMPAT flag? It means that
old ext4, ext3 and ext2 can only mount this fs read-only, yes?
Index: linux-2.6.22-rc4/fs/ext4/namei.c
===================================================================
--- linux-2.6.22-rc4.orig/fs/ext4/namei.c 2007-06-14 17:30:47.000000000 -0700
+++ linux-2.6.22-rc4/fs/ext4/namei.c 2007-06-14 17:32:55.000000000 -0700
@@ -1619,6 +1619,27 @@ static int ext4_delete_entry (handle_t *
return -ENOENT;
}
+static inline 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);
+ }
+ }
+}
Looks too big to be inlined.
Why do we set EXT4_FEATURE_RO_COMPAT_DIR_NLINK if i_nlink==2?
+static inline 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);
+}
Probably too big to inline.
+
static int ext4_add_nondir(handle_t *handle,
struct dentry *dentry, struct inode *inode)
{
@@ -1715,7 +1736,7 @@ static int ext4_mkdir(struct inode * dir
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:
@@ -1738,7 +1759,7 @@ 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;
@@ -1770,7 +1791,7 @@ 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);
@@ -2035,10 +2056,10 @@ static int ext4_rmdir (struct inode * di
retval = ext4_delete_entry(handle, dir, de, bh);
if (retval)
goto end_rmdir;
- if (inode->i_nlink != 2)
- ext4_warning (inode->i_sb, "ext4_rmdir",
- "empty directory has nlink!=2 (%d)",
- inode->i_nlink);
+ if (!EXT4_DIR_LINK_EMPTY(inode))
+ ext4_warning(inode->i_sb, "ext4_rmdir",
+ "empty directory has too many links (%d)",
+ inode->i_nlink);
inode->i_version++;
clear_nlink(inode);
/* There's no need to set i_disksize: the fact that i_nlink is
@@ -2048,7 +2069,7 @@ static int ext4_rmdir (struct inode * di
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);
@@ -2099,7 +2120,7 @@ static int ext4_unlink(struct inode * di
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);
@@ -2149,7 +2170,7 @@ 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;
@@ -2175,8 +2196,9 @@ static int ext4_link (struct dentry * ol
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;
argh. WHY_IS_EXT4_FULL_OF_UPPER_CASE_MACROS_WHICH_COULD_BE_IMPLEMENTED
as_lower_case_inlines? Sigh. It's all the old-timers, I guess.
EXT4_DIR_LINK_MAX() is buggy: it evaluates its arg twice.
/*
* Return -ENOENT if we've raced with unlink and i_nlink is 0. Doing
* otherwise has the potential to corrupt the orphan inode list.
@@ -2194,7 +2216,7 @@ 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);
@@ -2327,7 +2349,7 @@ static int ext4_rename (struct inode * o
}
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);
@@ -2338,11 +2360,13 @@ static int ext4_rename (struct inode * o
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);
}
-
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