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    Subject[PATCH 3/7] autofs4 - fix pending checks
    Date
    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@themaw.net>

    ---

    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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