On Thu 22-05-14 03:48:59, hooanon05g@xxxxxxxxx wrote:
> From: "J. R. Okajima" <hooanon05g@xxxxxxxxx>
>
> Add a feature to keep the uniqueness of inum in the superblock.
> In this commit, the parameter superblock sets NULL, so the feature is
> OFF. It will be ON individually be thier maintainer.
>
> Signed-off-by: J. R. Okajima <hooanon05g@xxxxxxxxx>
...
> diff --git a/fs/inode.c b/fs/inode.c
> index a3e274a..1412607 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -834,8 +834,9 @@ repeat:
> #define LAST_INO_BATCH 1024
> static DEFINE_PER_CPU(unsigned int, last_ino);
>
> -unsigned int get_next_ino(void)
> +static unsigned int do_get_next_ino(struct super_block *sb, int *pwrapped)
> {
> + static int wrapped;
> unsigned int *p = &get_cpu_var(last_ino);
> unsigned int res = *p;
>
> @@ -850,10 +851,60 @@ unsigned int get_next_ino(void)
>
> res++;
> /* never zero */
> - if (unlikely(!res))
> + if (unlikely(!res)) {
> res++;
> + wrapped = 1;
> + }
> *p = res;
> put_cpu_var(last_ino);
> + *pwrapped = wrapped;
> + return res;
> +}
> +
> +static int test_ino_sb(struct super_block *sb, unsigned long ino)
> +{
> + int in_use;
> + struct inode *inode, *next;
> +
> + in_use = 0;
> + spin_lock(&inode_sb_list_lock);
> + list_for_each_entry_safe(inode, next, &sb->s_inodes, i_sb_list) {
> + if (inode->i_ino != ino)
> + continue;
> + in_use = 1;
> + break;
> + }
> + spin_unlock(&inode_sb_list_lock);
> +
> + return in_use;
> +}
I don't think scanning the whole superblock list is really a viable
alternative. That is going to contend a lot on inode_sb_list_lock and burn
a lot of CPU when there is even moderate number of inodes in tmpfs. If we
ever have to really use unique inode numbers for tmpfs (but I'm not
convinced - see my other email), we should probably hash those inodes and
use iunique()...
Honza
--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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