Re: [PATCH 3/7] sysfs: Keep an nlink count on sysfs directories.

Eric W. Biederman
2010-01-12T15:35:05Z

Cornelia Huck <cornelia.huck@de.ibm.com> writes:

> On Mon, 11 Jan 2010 12:21:51 -0800,
> "Eric W. Biederman" <ebiederm@xmission.com> wrote:
>
>> From: Eric W. Biederman <ebiederm@aristanetworks.com>
>>
>> On large directories sysfs_count_nlinks can be a significant
>> bottleneck, so keep a count in sysfs_dirent. If we exceed
>> the maximum number of directory entries we can store return
>> nlink of 1. An nlink of 1 matches what reiserfs does in
>> this case, and it let's find and similar utlities know that
>> we have a the directory nlink can not be used for optimization
>> purposes.
>>
>> Signed-off-by: Eric W. Biederman <ebiederm@aristanetworks.com>
>> ---
>> fs/sysfs/dir.c | 20 ++++++++++++++++++++
>> fs/sysfs/inode.c | 15 +--------------
>> fs/sysfs/mount.c | 1 +
>> fs/sysfs/sysfs.h | 1 +
>> 4 files changed, 23 insertions(+), 14 deletions(-)
>>
>
>> @@ -420,6 +438,7 @@ int __sysfs_add_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd)
>> return -EEXIST;
>>
>> sd->s_parent = sysfs_get(acxt->parent_sd);
>> + sysfs_dir_inc_nlink(sd->s_parent);
>>
>> sysfs_link_sibling(sd);
>>
>> @@ -512,6 +531,7 @@ void sysfs_remove_one(struct sysfs_addrm_cxt *acxt, struct sysfs_dirent *sd)
>>
>> BUG_ON(sd->s_flags & SYSFS_FLAG_REMOVED);
>>
>> + sysfs_dir_dec_nlink(sd->s_parent);
>> sysfs_unlink_sibling(sd);
>>
>> /* Update timestamps on the parent */
>
> Shouldn't s_nlink be adjusted in sysfs_rename for the move case as well?

Yes. I hereby nominate this as my most buggy patch ever.
Ugh.

I thought I actually cared about nlinks when I bothered to keep a
nlink count, but I am starting to think I really don't.

Eric