On Thu, 2011-01-13 at 21:54 +0000, David Howells wrote:
> From: Ian Kent <raven@xxxxxxxxxx>
>
> This patch required a previous patch to add the ->d_automount()
> dentry operation.
>
> Add a function to use the newly defined ->d_manage() dentry operation
> for blocking during mount and expire.
>
> Whether the VFS calls the dentry operations d_automount() and d_manage()
> is controled by the DMANAGED_AUTOMOUNT and DMANAGED_TRANSIT flags. autofs
> uses the d_automount() operation to callback to user space to request
> mount operations and the d_manage() operation to block walks into mounts
> that are under construction or destruction.
>
> In order to prevent these functions from being called unnecessarily the
> DMANAGED_* flags are cleared for cases which would cause this. In the
> common case the DMANAGED_AUTOMOUNT and DMANAGED_TRANSIT flags are both
> set for dentrys waiting to be mounted. The DMANAGED_TRANSIT flag is
> cleared upon successful mount request completion and set during expire
> runs, both during the dentry expire check, and if selected for expire,
> is left set until a subsequent successful mount request completes.
>
> The exception to this is the so-called rootless multi-mount which has
> no actual mount at its base. In this case the DMANAGED_AUTOMOUNT flag
> is cleared upon successful mount request completion as well and set
> again after a successful expire.
>
> Signed-off-by: Ian Kent <raven@xxxxxxxxxx>
> Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
> ---
>
> fs/autofs4/autofs_i.h | 50 ++++++++++++++++++++++++-
> fs/autofs4/expire.c | 51 +++++++++++++------------
> fs/autofs4/inode.c | 3 +
> fs/autofs4/root.c | 100 +++++++++++++++++++++++++++++++++++++++++++------
> 4 files changed, 164 insertions(+), 40 deletions(-)
>
> diff --git a/fs/autofs4/autofs_i.h b/fs/autofs4/autofs_i.h
> index 1ebfe53..7eff538 100644
> --- a/fs/autofs4/autofs_i.h
> +++ b/fs/autofs4/autofs_i.h
> @@ -99,7 +99,6 @@ struct autofs_info {
> };
>
> #define AUTOFS_INF_EXPIRING (1<<0) /* dentry is in the process of expiring */
> -#define AUTOFS_INF_MOUNTPOINT (1<<1) /* mountpoint status for direct expire */
> #define AUTOFS_INF_PENDING (1<<2) /* dentry pending mount */
>
> struct autofs_wait_queue {
> @@ -221,6 +220,7 @@ extern const struct file_operations autofs4_root_operations;
> /* Operations methods */
>
> struct vfsmount *autofs4_d_automount(struct path *);
> +int autofs4_d_manage(struct path *, bool);
>
> /* VFS automount flags management functions */
>
> @@ -248,6 +248,54 @@ static inline void managed_dentry_clear_automount(struct dentry *dentry)
> spin_unlock(&dentry->d_lock);
> }
>
> +static inline void __managed_dentry_set_transit(struct dentry *dentry)
> +{
> + dentry->d_flags |= DCACHE_MANAGE_TRANSIT;
> +}
> +
> +static inline void managed_dentry_set_transit(struct dentry *dentry)
> +{
> + spin_lock(&dentry->d_lock);
> + __managed_dentry_set_transit(dentry);
> + spin_unlock(&dentry->d_lock);
> +}
> +
> +static inline void __managed_dentry_clear_transit(struct dentry *dentry)
> +{
> + dentry->d_flags &= ~DCACHE_MANAGE_TRANSIT;
> +}
> +
> +static inline void managed_dentry_clear_transit(struct dentry *dentry)
> +{
> + spin_lock(&dentry->d_lock);
> + __managed_dentry_clear_transit(dentry);
> + spin_unlock(&dentry->d_lock);
> +}
> +
> +static inline void __managed_dentry_set_managed(struct dentry *dentry)
> +{
> + dentry->d_flags |= (DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT);
> +}
> +
> +static inline void managed_dentry_set_managed(struct dentry *dentry)
> +{
> + spin_lock(&dentry->d_lock);
> + __managed_dentry_set_managed(dentry);
> + spin_unlock(&dentry->d_lock);
> +}
> +
> +static inline void __managed_dentry_clear_managed(struct dentry *dentry)
> +{
> + dentry->d_flags &= ~(DCACHE_NEED_AUTOMOUNT|DCACHE_MANAGE_TRANSIT);
> +}
> +
> +static inline void managed_dentry_clear_managed(struct dentry *dentry)
> +{
> + spin_lock(&dentry->d_lock);
> + __managed_dentry_clear_managed(dentry);
> + spin_unlock(&dentry->d_lock);
> +}
> +
> /* Initializing function */
>
> int autofs4_fill_super(struct super_block *, void *, int);
> diff --git a/fs/autofs4/expire.c b/fs/autofs4/expire.c
> index 0571ec8..3ed79d7 100644
> --- a/fs/autofs4/expire.c
> +++ b/fs/autofs4/expire.c
> @@ -26,10 +26,6 @@ static inline int autofs4_can_expire(struct dentry *dentry,
> if (ino == NULL)
> return 0;
>
> - /* No point expiring a pending mount */
> - if (ino->flags & AUTOFS_INF_PENDING)
> - return 0;
> -
> if (!do_now) {
> /* Too young to die */
> if (!timeout || time_after(ino->last_used + timeout, now))
> @@ -283,6 +279,7 @@ struct dentry *autofs4_expire_direct(struct super_block *sb,
> unsigned long timeout;
> struct dentry *root = dget(sb->s_root);
> int do_now = how & AUTOFS_EXP_IMMEDIATE;
> + struct autofs_info *ino;
>
> if (!root)
> return NULL;
> @@ -291,20 +288,21 @@ struct dentry *autofs4_expire_direct(struct super_block *sb,
> timeout = sbi->exp_timeout;
>
> spin_lock(&sbi->fs_lock);
> + ino = autofs4_dentry_ino(root);
> + /* No point expiring a pending mount */
> + if (ino->flags & AUTOFS_INF_PENDING) {
> + spin_unlock(&sbi->fs_lock);
> + return NULL;
> + }
> + managed_dentry_set_transit(root);
> if (!autofs4_direct_busy(mnt, root, timeout, do_now)) {
> struct autofs_info *ino = autofs4_dentry_ino(root);
> - if (d_mountpoint(root)) {
> - ino->flags |= AUTOFS_INF_MOUNTPOINT;
> - spin_lock(&root->d_lock);
> - root->d_flags &= ~DCACHE_MOUNTED;
> - spin_unlock(&root->d_lock);
> - }
> ino->flags |= AUTOFS_INF_EXPIRING;
> - managed_dentry_set_automount(root);
> init_completion(&ino->expire_complete);
> spin_unlock(&sbi->fs_lock);
> return root;
> }
> + managed_dentry_clear_transit(root);
> spin_unlock(&sbi->fs_lock);
> dput(root);
>
> @@ -341,6 +339,10 @@ struct dentry *autofs4_expire_indirect(struct super_block *sb,
> while ((dentry = get_next_positive_dentry(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 cont;
> + managed_dentry_set_transit(dentry);
>
> /*
> * Case 1: (i) indirect mount or top level pseudo direct mount
> @@ -400,6 +402,8 @@ struct dentry *autofs4_expire_indirect(struct super_block *sb,
> }
> }
> next:
> + managed_dentry_clear_transit(dentry);
> +cont:
> spin_unlock(&sbi->fs_lock);
> }
> return NULL;
> @@ -409,7 +413,6 @@ found:
> expired, (int)expired->d_name.len, expired->d_name.name);
> ino = autofs4_dentry_ino(expired);
> ino->flags |= AUTOFS_INF_EXPIRING;
> - managed_dentry_set_automount(expired);
> init_completion(&ino->expire_complete);
> spin_unlock(&sbi->fs_lock);
> spin_lock(&autofs4_lock);
> @@ -482,7 +485,7 @@ int autofs4_expire_run(struct super_block *sb,
> ino = autofs4_dentry_ino(dentry);
> ino->flags &= ~AUTOFS_INF_EXPIRING;
> if (!d_unhashed(dentry))
> - managed_dentry_clear_automount(dentry);
> + managed_dentry_clear_transit(dentry);
> complete_all(&ino->expire_complete);
> spin_unlock(&sbi->fs_lock);
>
> @@ -508,20 +511,18 @@ int autofs4_do_expire_multi(struct super_block *sb, struct vfsmount *mnt,
> ret = autofs4_wait(sbi, dentry, NFY_EXPIRE);
>
> spin_lock(&sbi->fs_lock);
> - if (ino->flags & AUTOFS_INF_MOUNTPOINT) {
> - spin_lock(&sb->s_root->d_lock);
> - /*
> - * If we haven't been expired away, then reset
> - * mounted status.
> - */
> - if (mnt->mnt_parent != mnt)
> - sb->s_root->d_flags |= DCACHE_MOUNTED;
> - spin_unlock(&sb->s_root->d_lock);
> - ino->flags &= ~AUTOFS_INF_MOUNTPOINT;
> - }
> ino->flags &= ~AUTOFS_INF_EXPIRING;
> + spin_lock(&dentry->d_lock);
> if (ret)
> - managed_dentry_clear_automount(dentry);
> + __managed_dentry_clear_transit(dentry);
> + else {
> + if ((IS_ROOT(dentry) ||
> + (autofs_type_indirect(sbi->type) &&
> + IS_ROOT(dentry->d_parent))) &&
> + !(dentry->d_flags & DCACHE_NEED_AUTOMOUNT))
> + __managed_dentry_set_automount(dentry);
> + }
> + spin_unlock(&dentry->d_lock);
> complete_all(&ino->expire_complete);
> spin_unlock(&sbi->fs_lock);
> dput(dentry);
> diff --git a/fs/autofs4/inode.c b/fs/autofs4/inode.c
> index d0aa38c..75c1ed8 100644
> --- a/fs/autofs4/inode.c
> +++ b/fs/autofs4/inode.c
> @@ -253,6 +253,7 @@ static struct autofs_info *autofs4_mkroot(struct autofs_sb_info *sbi)
>
> static const struct dentry_operations autofs4_sb_dentry_operations = {
> .d_automount = autofs4_d_automount,
> + .d_manage = autofs4_d_manage,
> .d_release = autofs4_dentry_release,
> };
>
> @@ -322,7 +323,7 @@ int autofs4_fill_super(struct super_block *s, void *data, int silent)
> }
>
> if (autofs_type_trigger(sbi->type))
> - __managed_dentry_set_automount(root);
> + __managed_dentry_set_managed(root);
>
> root_inode->i_fop = &autofs4_root_operations;
> root_inode->i_op = autofs_type_trigger(sbi->type) ?
> diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
> index bf8a69d..b2cc422 100644
> --- a/fs/autofs4/root.c
> +++ b/fs/autofs4/root.c
> @@ -424,6 +424,7 @@ static const struct dentry_operations autofs4_root_dentry_operations = {
> /* For other dentries */
> static const struct dentry_operations autofs4_dentry_operations = {
> .d_automount = autofs4_d_automount,
> + .d_manage = autofs4_d_manage,
> .d_release = autofs4_dentry_release,
> };
>
> @@ -604,6 +605,20 @@ struct vfsmount *autofs4_d_automount(struct path *path)
> DPRINTK("dentry=%p %.*s",
> dentry, dentry->d_name.len, dentry->d_name.name);
>
> + /*
> + * Someone may have manually umounted this or it was a submount
> + * that has gone away.
> + */
> + //spin_lock(&dcache_lock); /////////////// JUST DELETE THIS LOCK?
> + if (!d_mountpoint(dentry) && list_empty(&dentry->d_subdirs)) {
> + spin_lock(&dentry->d_lock);
> + if (!(dentry->d_flags & DCACHE_MANAGE_TRANSIT) &&
> + (dentry->d_flags & DCACHE_NEED_AUTOMOUNT))
> + __managed_dentry_set_transit(path->dentry);
> + spin_unlock(&dentry->d_lock);
> + }
> + //spin_unlock(&dcache_lock);
In this case I think the dcache_lock needs to be deleted and the d_lock
moved out of the if to protect the d_subdirs access.
Ian
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