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Message-ID: <1405497017.2527.89.camel@perseus.fritz.box>
Date: Wed, 16 Jul 2014 15:50:17 +0800
From: Ian Kent <raven@...maw.net>
To: NeilBrown <neilb@...e.de>
Cc: autofs@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/6 v2] autofs4: factor should_expire() out of
autofs4_expire_indirect.
On Mon, 2014-07-14 at 10:53 +1000, NeilBrown wrote:
> Here is a revised version of this one patch.
> This one fixes a problem with refcounts on dentry and adds a comment to
> clarify the behaviour of should_expire().
I had some problems with this patch.
Looked like it got munged by the email client.
I had to get rid of ^M line ends and fix several other translations and
wrapped lines.
Hopefully I didn't mess it up.
>
> thanks,
> NeilBrown
>
>
> From: NeilBrown <neilb@...e.de>Date: Tue, 8 Jul 2014 17:14:53 +1000
> Subject: [PATCH] autofs4: factor should_expire() out of autofs4_expire_indirect.
>
> Future patch will potentially call this twice, so make it
> separate.
>
> Signed-off-by: NeilBrown <neilb@...e.de>
>
> diff --git a/fs/autofs4/expire.c b/fs/autofs4/expire.c
> index 7e2f22ce6954..402ee7f1461a 100644
> --- a/fs/autofs4/expire.c
> +++ b/fs/autofs4/expire.c
> @@ -345,6 +345,89 @@ out:
> return NULL;
> }
>
> +/* Check if 'dentry' should expire, or return a nearby
> + * dentry that is suitable.
> + * If returned dentry is different from arg dentry,
> + * then a dget() reference was taken, else not.
> + */
> +static struct dentry *should_expire(struct dentry *dentry,
> + struct vfsmount *mnt,
> + unsigned long timeout,
> + int how)
> +{
> + int do_now = how & AUTOFS_EXP_IMMEDIATE;
> + int exp_leaves = how & AUTOFS_EXP_LEAVES;
> + struct autofs_info *ino = autofs4_dentry_ino(dentry);
> + unsigned int ino_count;
> +
> + /* No point expiring a pending mount */
> + if (ino->flags & AUTOFS_INF_PENDING)
> + return NULL;
> +
> + /*
> + * Case 1: (i) indirect mount or top level pseudo direct mount
> + * (autofs-4.1).
> + * (ii) indirect mount with offset mount, check the "/"
> + * offset (autofs-5.0+).
> + */
> + if (d_mountpoint(dentry)) {
> + DPRINTK("checking mountpoint %p %.*s",
> + dentry, (int)dentry->d_name.len, dentry->d_name.name);
> +
> + /* Can we umount this guy */
> + if (autofs4_mount_busy(mnt, dentry))
> + return NULL;
> +
> + /* Can we expire this guy */
> + if (autofs4_can_expire(dentry, timeout, do_now))
> + return dentry;
> + return NULL;
> + }
> +
> + if (dentry->d_inode && S_ISLNK(dentry->d_inode->i_mode)) {
> + DPRINTK("checking symlink %p %.*s",
> + dentry, (int)dentry->d_name.len, dentry->d_name.name);
> + /*
> + * A symlink can't be "busy" in the usual sense so
> + * just check last used for expire timeout.
> + */
> + if (autofs4_can_expire(dentry, timeout, do_now))
> + return dentry;
> + return NULL;
> + }
> +
> + if (simple_empty(dentry))
> + return NULL;
> +
> + /* Case 2: tree mount, expire iff entire tree is not busy */
> + if (!exp_leaves) {
> + /* Path walk currently on this dentry? */
> + ino_count = atomic_read(&ino->count) + 1;
> + if (d_count(dentry) > ino_count)
> + return NULL;
> +
> + if (!autofs4_tree_busy(mnt, dentry, timeout, do_now))
> + return dentry;
> + /*
> + * Case 3: pseudo direct mount, expire individual leaves
> + * (autofs-4.1).
> + */
I recommend removing one of the tab stops on this since it relates to
the else case but feels like it's "attached" to the code above the else.
> + } else {
> + /* Path walk currently on this dentry? */
> + struct dentry *expired;
> + ino_count = atomic_read(&ino->count) + 1;
> + if (d_count(dentry) > ino_count)
> + return NULL;
> +
> + expired = autofs4_check_leaves(mnt, dentry, timeout, do_now);
> + if (expired) {
> + if (expired == dentry)
> + dput(dentry);
> + return dentry;
Umm .. I think this should be "return expired".
Otherwise this looks like a straight refactor.
> + }
> + }
> + return NULL;
> +}
> /*
> * Find an eligible tree to time-out
> * A tree is eligible if :-
> @@ -359,11 +442,8 @@ struct dentry *autofs4_expire_indirect(struct super_block *sb,
> unsigned long timeout;
> struct dentry *root = sb->s_root;
> struct dentry *dentry;
> - struct dentry *expired = NULL;
> - int do_now = how & AUTOFS_EXP_IMMEDIATE;
> - int exp_leaves = how & AUTOFS_EXP_LEAVES;
> + struct dentry *expired;
> struct autofs_info *ino;
> - unsigned int ino_count;
>
> if (!root)
> return NULL;
> @@ -374,78 +454,12 @@ struct dentry *autofs4_expire_indirect(struct super_block *sb,
> dentry = NULL;
> while ((dentry = get_next_positive_subdir(dentry, root))) {
> spin_lock(&sbi->fs_lock);
> - ino = autofs4_dentry_ino(dentry);
> - /* No point expiring a pending mount */
> - if (ino->flags & AUTOFS_INF_PENDING)
> - goto next;
> -
> - /*
> - * Case 1: (i) indirect mount or top level pseudo direct mount
> - * (autofs-4.1).
> - * (ii) indirect mount with offset mount, check the "/"
> - * offset (autofs-5.0+).
> - */
> - if (d_mountpoint(dentry)) {
> - DPRINTK("checking mountpoint %p %.*s",
> - dentry, (int)dentry->d_name.len, dentry->d_name.name);
> -
> - /* Can we umount this guy */
> - if (autofs4_mount_busy(mnt, dentry))
> - goto next;
> -
> - /* Can we expire this guy */
> - if (autofs4_can_expire(dentry, timeout, do_now)) {
> - expired = dentry;
> - goto found;
> - }
> - goto next;
> - }
> -
> - if (dentry->d_inode && S_ISLNK(dentry->d_inode->i_mode)) {
> - DPRINTK("checking symlink %p %.*s",
> - dentry, (int)dentry->d_name.len, dentry->d_name.name);
> - /*
> - * A symlink can't be "busy" in the usual sense so
> - * just check last used for expire timeout.
> - */
> - if (autofs4_can_expire(dentry, timeout, do_now)) {
> - expired = dentry;
> - goto found;
> - }
> - goto next;
> - }
> -
> - if (simple_empty(dentry))
> - goto next;
> -
> - /* Case 2: tree mount, expire iff entire tree is not busy */
> - if (!exp_leaves) {
> - /* Path walk currently on this dentry? */
> - ino_count = atomic_read(&ino->count) + 1;
> - if (d_count(dentry) > ino_count)
> - goto next;
> -
> - if (!autofs4_tree_busy(mnt, dentry, timeout, do_now)) {
> - expired = dentry;
> - goto found;
> - }
> - /*
> - * Case 3: pseudo direct mount, expire individual leaves
> - * (autofs-4.1).
> - */
> - } else {
> - /* Path walk currently on this dentry? */
> - ino_count = atomic_read(&ino->count) + 1;
> - if (d_count(dentry) > ino_count)
> - goto next;
> -
> - expired = autofs4_check_leaves(mnt, dentry, timeout, do_now);
> - if (expired) {
> + expired = should_expire(dentry, mnt, timeout, how);
> + if (expired) {
> + if (expired != dentry)
> dput(dentry);
> - goto found;
> - }
> + goto found;
> }
> -next:
> spin_unlock(&sbi->fs_lock);
> }
> return NULL;
--
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