Ian Kent <raven@xxxxxxxxxx> writes:
> There are two cases for which a dentry that has a pending mount request
> does not wait for completion. One is via autofs4_revalidate() and the
> other via autofs4_follow_link().
>
> In revalidate, after the mount point directory is created, but before
> the mount is done, the check in try_to_fill_dentry() can can fail to
> send the dentry to the wait queue since the dentry is positive and the
> lookup flags may contain only LOOKUP_FOLLOW. Although we don't trigger
> a mount for the LOOKUP_FOLLOW flag, if ther's one pending we might as
> well wait and use the mounted dentry for the lookup.
>
> In autofs4_follow_link() the dentry is not checked to see if it is
> pending so it may fail to call try_to_fill_dentry() and not wait
> for mount completion.
>
> A dentry that is pending must always be sent to the wait queue.
>
> Signed-off-by: Ian Kent <raven@xxxxxxxxxx>
Reviewed-by: Jeff Moyer <jmoyer@xxxxxxxxxx>
>
> ---
>
> fs/autofs4/root.c | 9 ++++++---
> 1 files changed, 6 insertions(+), 3 deletions(-)
>
>
> diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
> index e842b0a..2944b28 100644
> --- a/fs/autofs4/root.c
> +++ b/fs/autofs4/root.c
> @@ -177,7 +177,8 @@ static int try_to_fill_dentry(struct dentry *dentry, int flags)
> return status;
> }
> /* Trigger mount for path component or follow link */
> - } else if (flags & (TRIGGER_FLAGS | TRIGGER_INTENTS) ||
> + } else if (dentry->d_flags & DCACHE_AUTOFS_PENDING ||
> + flags & (TRIGGER_FLAGS | TRIGGER_INTENTS) ||
> current->link_count) {
> DPRINTK("waiting for mount name=%.*s",
> dentry->d_name.len, dentry->d_name.name);
> @@ -223,7 +224,8 @@ static void *autofs4_follow_link(struct dentry *dentry, struct nameidata *nd)
>
> /* If it's our master or we shouldn't trigger a mount we're done */
> lookup_type = nd->flags & (TRIGGER_FLAGS | TRIGGER_INTENTS);
> - if (oz_mode || !lookup_type)
> + if (oz_mode ||
> + !(lookup_type || dentry->d_flags & DCACHE_AUTOFS_PENDING))
> goto done;
>
> /* If an expire request is pending wait for it. */
> @@ -242,7 +244,8 @@ static void *autofs4_follow_link(struct dentry *dentry, struct nameidata *nd)
> * don't try to mount it again.
> */
> spin_lock(&dcache_lock);
> - if (!d_mountpoint(dentry) && __simple_empty(dentry)) {
> + if (dentry->d_flags & DCACHE_AUTOFS_PENDING ||
> + (!d_mountpoint(dentry) && __simple_empty(dentry))) {
> spin_unlock(&dcache_lock);
>
> status = try_to_fill_dentry(dentry, 0);
> --
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