On Mon, Nov 27 2017, Ian Kent wrote:
> While the patch of commit 092a53452b helped (partially) resolve a
> problem where automounts were not expiring due to aggressive accesses
> from user space it has a side effect for very large environments.
>
> This change helps with the expire problem by making the expire more
> aggressive but, for very large environments, that means more mount
> requests from clients. When there are a lot of clients that can mean
> fairly significant server load increases.
>
> It turns out I put the last_used in this position to solve this
> very problem and failed to update my own thinking of the autofs
> expire policy. So the patch being reverted introduces a regression
> which should be fixed.
>
> Reverts: 092a53452b
I would add:
Fixes: 092a53452bb7 ("autofs: take more care to not update last_used on path walk")
Cc: stable@xxxxxxxxxxxxxxx (v4.11+)
to ensure these are picked up as needed (different Fixes line for second
of course).
Reviewed-by: NeilBrown <neilb@xxxxxxxx>
Thanks,
NeilBrown
>
> Signed-off-by: Ian Kent <raven@xxxxxxxxxx>
> Cc: Neil Brown <neilb@xxxxxxxx>
> Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> ---
> fs/autofs4/root.c | 17 ++++++-----------
> 1 file changed, 6 insertions(+), 11 deletions(-)
>
> diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
> index d79ced925861..82e8f6edfb48 100644
> --- a/fs/autofs4/root.c
> +++ b/fs/autofs4/root.c
> @@ -281,8 +281,8 @@ static int autofs4_mount_wait(const struct path *path, bool rcu_walk)
> pr_debug("waiting for mount name=%pd\n", path->dentry);
> status = autofs4_wait(sbi, path, NFY_MOUNT);
> pr_debug("mount wait done status=%d\n", status);
> - ino->last_used = jiffies;
> }
> + ino->last_used = jiffies;
> return status;
> }
>
> @@ -321,21 +321,16 @@ static struct dentry *autofs4_mountpoint_changed(struct path *path)
> */
> if (autofs_type_indirect(sbi->type) && d_unhashed(dentry)) {
> struct dentry *parent = dentry->d_parent;
> + struct autofs_info *ino;
> struct dentry *new;
>
> new = d_lookup(parent, &dentry->d_name);
> if (!new)
> return NULL;
> - if (new == dentry)
> - dput(new);
> - else {
> - struct autofs_info *ino;
> -
> - ino = autofs4_dentry_ino(new);
> - ino->last_used = jiffies;
> - dput(path->dentry);
> - path->dentry = new;
> - }
> + ino = autofs4_dentry_ino(new);
> + ino->last_used = jiffies;
> + dput(path->dentry);
> + path->dentry = new;
> }
> return path->dentry;
> }
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