Messages in this thread Patch in this message | | | Subject | [PATCH 4/4] autofs: add comment about autofs_mountpoint_changed() | From | Ian Kent <> | Date | Thu, 26 Mar 2020 13:23:36 +0800 |
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The function autofs_mountpoint_changed() is unusual, add a comment about two cases for which it is used.
Signed-off-by: Ian Kent <raven@themaw.net> --- fs/autofs/root.c | 21 ++++++++++++++++++--- 1 file changed, 18 insertions(+), 3 deletions(-)
diff --git a/fs/autofs/root.c b/fs/autofs/root.c index 308cc49aca1d..a972bbaecb46 100644 --- a/fs/autofs/root.c +++ b/fs/autofs/root.c @@ -280,9 +280,24 @@ static struct dentry *autofs_mountpoint_changed(struct path *path) struct dentry *dentry = path->dentry; struct autofs_sb_info *sbi = autofs_sbi(dentry->d_sb); - /* - * If this is an indirect mount the dentry could have gone away - * as a result of an expire and a new one created. + /* If this is an indirect mount the dentry could have gone away + * and a new one created. + * + * This is unusual and I can't remember the case for which it + * was originally added now. But a example of how this can + * happen is an autofs indirect mount that has the "browse" + * option set and also has the "symlink" option in the autofs + * map entry. In this case the daemon will remove the browse + * directory and create a symlink as the mount (pointing to a + * local path) leaving the struct path stale. + * + * Another not so obvious case is when a mount in an autofs + * indirect mount that uses the "nobrowse" option is being + * expired and the mount has been umounted but the mount point + * directory remains when a stat family system call is made. + * In this case the mount point is removed (by the daemon) and + * a new mount triggered leading to a stale dentry in the struct + * path of the waiting process. */ if (autofs_type_indirect(sbi->type) && d_unhashed(dentry)) { struct dentry *parent = dentry->d_parent;
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