Nick Piggin wrote:
>
> Cool, well I look forward to your reviewing the changes when I get
> a bit further down the track. In the meantime, here is the d_mounted
> patch diffed against rc3.
The autofs4 bit of the patch below isn't quite how this is supposed to
work. I'll have a look and see if I can make the appropriate change.
>
> --
>
> Rather than keep a d_mounted count in the dentry (which is only used to
> speculatively take a look in the mount hash table if it is non-zero), set
> a dentry flag instead. The flag can be cleared by checking the hash table
> to see if there are any mounts left. It is not time critical because it
> is performed at detach time.
>
> This saves 4 bytes on 32-bit, nothing on 64-bit but it does provide a hole
> which I might use later.
> ---
> fs/autofs4/expire.c | 8 ++++++--
> fs/dcache.c | 1 -
> fs/namespace.c | 19 +++++++++++++++----
> include/linux/dcache.h | 42 +++++++++++++++++++++---------------------
> 4 files changed, 42 insertions(+), 28 deletions(-)
>
> Index: linux-2.6/fs/dcache.c
> ===================================================================
> --- linux-2.6.orig/fs/dcache.c
> +++ linux-2.6/fs/dcache.c
> @@ -947,7 +947,6 @@ struct dentry *d_alloc(struct dentry * p
> dentry->d_sb = NULL;
> dentry->d_op = NULL;
> dentry->d_fsdata = NULL;
> - dentry->d_mounted = 0;
> INIT_HLIST_NODE(&dentry->d_hash);
> INIT_LIST_HEAD(&dentry->d_lru);
> INIT_LIST_HEAD(&dentry->d_subdirs);
> Index: linux-2.6/fs/namespace.c
> ===================================================================
> --- linux-2.6.orig/fs/namespace.c
> +++ linux-2.6/fs/namespace.c
> @@ -467,6 +467,15 @@ static void __touch_mnt_namespace(struct
> }
> }
>
> +static void dentry_reset_mounted(struct vfsmount *mnt, struct dentry *dentry)
> +{
> + if (!__lookup_mnt(mnt, dentry, 0)) {
> + spin_lock(&dentry->d_lock);
> + dentry->d_flags &= ~DCACHE_MOUNTED;
> + spin_unlock(&dentry->d_lock);
> + }
> +}
> +
> static void detach_mnt(struct vfsmount *mnt, struct path *old_path)
> {
> old_path->dentry = mnt->mnt_mountpoint;
> @@ -475,15 +484,17 @@ static void detach_mnt(struct vfsmount *
> mnt->mnt_mountpoint = mnt->mnt_root;
> list_del_init(&mnt->mnt_child);
> list_del_init(&mnt->mnt_hash);
> - old_path->dentry->d_mounted--;
> + dentry_reset_mounted(old_path->mnt, old_path->dentry);
> }
>
> void mnt_set_mountpoint(struct vfsmount *mnt, struct dentry *dentry,
> struct vfsmount *child_mnt)
> {
> child_mnt->mnt_parent = mntget(mnt);
> - child_mnt->mnt_mountpoint = dget(dentry);
> - dentry->d_mounted++;
> + spin_lock(&dentry->d_lock);
> + child_mnt->mnt_mountpoint = dget_dlock(dentry);
> + dentry->d_flags |= DCACHE_MOUNTED;
> + spin_unlock(&dentry->d_lock);
> }
>
> static void attach_mnt(struct vfsmount *mnt, struct path *path)
> @@ -1015,7 +1026,7 @@ void umount_tree(struct vfsmount *mnt, i
> list_del_init(&p->mnt_child);
> if (p->mnt_parent != p) {
> p->mnt_parent->mnt_ghosts++;
> - p->mnt_mountpoint->d_mounted--;
> + dentry_reset_mounted(p->mnt_parent, p->mnt_mountpoint);
> }
> change_mnt_propagation(p, MS_PRIVATE);
> }
> Index: linux-2.6/include/linux/dcache.h
> ===================================================================
> --- linux-2.6.orig/include/linux/dcache.h
> +++ linux-2.6/include/linux/dcache.h
> @@ -83,14 +83,13 @@ full_name_hash(const unsigned char *name
> #ifdef CONFIG_64BIT
> #define DNAME_INLINE_LEN_MIN 32 /* 192 bytes */
> #else
> -#define DNAME_INLINE_LEN_MIN 40 /* 128 bytes */
> +#define DNAME_INLINE_LEN_MIN 44 /* 128 bytes */
> #endif
>
> struct dentry {
> atomic_t d_count;
> unsigned int d_flags; /* protected by d_lock */
> spinlock_t d_lock; /* per dentry lock */
> - int d_mounted;
> struct inode *d_inode; /* Where the name belongs to - NULL is
> * negative */
> /*
> @@ -161,30 +160,31 @@ d_iput: no no no
> yes
>
> /* d_flags entries */
> #define DCACHE_AUTOFS_PENDING 0x0001 /* autofs: "under construction" */
> -#define DCACHE_NFSFS_RENAMED 0x0002 /* this dentry has been "silly
> - * renamed" and has to be
> - * deleted on the last dput()
> - */
> -#define DCACHE_DISCONNECTED 0x0004
> - /* This dentry is possibly not currently connected to the dcache tree,
> - * in which case its parent will either be itself, or will have this
> - * flag as well. nfsd will not use a dentry with this bit set, but will
> - * first endeavour to clear the bit either by discovering that it is
> - * connected, or by performing lookup operations. Any filesystem which
> - * supports nfsd_operations MUST have a lookup function which, if it
> finds
> - * a directory inode with a DCACHE_DISCONNECTED dentry, will d_move
> - * that dentry into place and return that dentry rather than the passed
> one,
> - * typically using d_splice_alias.
> - */
> +#define DCACHE_NFSFS_RENAMED 0x0002
> + /* this dentry has been "silly renamed" and has to be deleted on the
> last
> + * dput() */
> +
> +#define DCACHE_DISCONNECTED 0x0004
> + /* This dentry is possibly not currently connected to the dcache tree,
> in
> + * which case its parent will either be itself, or will have this flag
> as
> + * well. nfsd will not use a dentry with this bit set, but will first
> + * endeavour to clear the bit either by discovering that it is
> connected,
> + * or by performing lookup operations. Any filesystem which supports
> + * nfsd_operations MUST have a lookup function which, if it finds a
> + * directory inode with a DCACHE_DISCONNECTED dentry, will d_move that
> + * dentry into place and return that dentry rather than the passed one,
> + * typically using d_splice_alias. */
>
> #define DCACHE_REFERENCED 0x0008 /* Recently used, don't discard. */
> #define DCACHE_UNHASHED 0x0010
> -
> -#define DCACHE_INOTIFY_PARENT_WATCHED 0x0020 /* Parent inode is
> watched by inotify */
> +#define DCACHE_INOTIFY_PARENT_WATCHED 0x0020
> + /* Parent inode is watched by inotify */
>
> #define DCACHE_COOKIE 0x0040 /* For use by dcookie subsystem
> */
> +#define DCACHE_FSNOTIFY_PARENT_WATCHED 0x0080
> + /* Parent inode is watched by some fsnotify listener */
>
> -#define DCACHE_FSNOTIFY_PARENT_WATCHED 0x0080 /* Parent inode is
> watched by some fsnotify listener */
> +#define DCACHE_MOUNTED 0x0100 /* is a mountpoint */
>
> extern spinlock_t dcache_lock;
> extern seqlock_t rename_lock;
> @@ -372,7 +372,7 @@ extern void dput(struct dentry *);
>
> static inline int d_mountpoint(struct dentry *dentry)
> {
> - return dentry->d_mounted;
> + return dentry->d_flags & DCACHE_MOUNTED;
> }
>
> extern struct vfsmount *lookup_mnt(struct path *);
> Index: linux-2.6/fs/autofs4/expire.c
> ===================================================================
> --- linux-2.6.orig/fs/autofs4/expire.c
> +++ linux-2.6/fs/autofs4/expire.c
> @@ -276,7 +276,9 @@ struct dentry *autofs4_expire_direct(str
> struct autofs_info *ino = autofs4_dentry_ino(root);
> if (d_mountpoint(root)) {
> ino->flags |= AUTOFS_INF_MOUNTPOINT;
> - root->d_mounted--;
> + spin_lock(&root->d_lock);
> + root->d_flags &= ~DCACHE_MOUNTED;
> + spin_unlock(&root->d_lock);
> }
> ino->flags |= AUTOFS_INF_EXPIRING;
> init_completion(&ino->expire_complete);
> @@ -499,7 +501,9 @@ int autofs4_do_expire_multi(struct super
>
> spin_lock(&sbi->fs_lock);
> if (ino->flags & AUTOFS_INF_MOUNTPOINT) {
> - sb->s_root->d_mounted++;
> + spin_lock(&sb->s_root->d_lock);
> + sb->s_root->d_flags |= DCACHE_MOUNTED;
> + spin_unlock(&sb->s_root->d_lock);
> ino->flags &= ~AUTOFS_INF_MOUNTPOINT;
> }
> ino->flags &= ~AUTOFS_INF_EXPIRING;
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