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    Subject[PATCH 05/46] fs: change d_delete semantics
    Change d_delete from a dentry deletion notification to a dentry caching
    advise, more like ->drop_inode. Require it to be constant and idempotent,
    and not take d_lock. This is how all existing filesystems use the callback
    anyway.

    This makes fine grained dentry locking of dput and dentry lru scanning
    much simpler.

    Signed-off-by: Nick Piggin <npiggin@kernel.dk>
    ---
    Documentation/filesystems/porting | 9 +++++++++
    Documentation/filesystems/vfs.txt | 27 +++++++++++++--------------
    arch/ia64/kernel/perfmon.c | 2 +-
    fs/9p/vfs_dentry.c | 4 ++--
    fs/afs/dir.c | 4 ++--
    fs/btrfs/inode.c | 2 +-
    fs/coda/dir.c | 4 ++--
    fs/configfs/dir.c | 2 +-
    fs/dcache.c | 2 --
    fs/gfs2/dentry.c | 2 +-
    fs/hostfs/hostfs_kern.c | 2 +-
    fs/libfs.c | 2 +-
    fs/ncpfs/dir.c | 4 ++--
    fs/nfs/dir.c | 2 +-
    fs/proc/base.c | 2 +-
    fs/proc/generic.c | 2 +-
    fs/proc/proc_sysctl.c | 2 +-
    fs/sysfs/dir.c | 2 +-
    include/linux/dcache.h | 6 +++---
    net/sunrpc/rpc_pipe.c | 2 +-
    20 files changed, 45 insertions(+), 39 deletions(-)

    diff --git a/Documentation/filesystems/porting b/Documentation/filesystems/porting
    index b12c895..6d9d6c3 100644
    --- a/Documentation/filesystems/porting
    +++ b/Documentation/filesystems/porting
    @@ -318,3 +318,12 @@ if it's zero is not *and* *never* *had* *been* enough. Final unlink() and iput(
    may happen while the inode is in the middle of ->write_inode(); e.g. if you blindly
    free the on-disk inode, you may end up doing that while ->write_inode() is writing
    to it.
    +
    +---
    +[mandatory]
    +
    + .d_delete() now only advises the dcache as to whether or not to cache
    +unreferenced dentries, and is now only called when the dentry refcount goes to
    +0. Even on 0 refcount transition, it must be able to tolerate being called 0,
    +1, or more times (eg. constant, idempotent).
    +
    diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt
    index ed7e5ef..83c42d0 100644
    --- a/Documentation/filesystems/vfs.txt
    +++ b/Documentation/filesystems/vfs.txt
    @@ -841,9 +841,9 @@ defined:

    struct dentry_operations {
    int (*d_revalidate)(struct dentry *, struct nameidata *);
    - int (*d_hash) (struct dentry *, struct qstr *);
    - int (*d_compare) (struct dentry *, struct qstr *, struct qstr *);
    - int (*d_delete)(struct dentry *);
    + int (*d_hash)(struct dentry *, struct qstr *);
    + int (*d_compare)(struct dentry *, struct qstr *, struct qstr *);
    + int (*d_delete)(const struct dentry *);
    void (*d_release)(struct dentry *);
    void (*d_iput)(struct dentry *, struct inode *);
    char *(*d_dname)(struct dentry *, char *, int);
    @@ -858,9 +858,11 @@ struct dentry_operations {

    d_compare: called when a dentry should be compared with another

    - d_delete: called when the last reference to a dentry is
    - deleted. This means no-one is using the dentry, however it is
    - still valid and in the dcache
    + d_delete: called when the last reference to a dentry is dropped and the
    + dcache is deciding whether or not to cache it. Return 1 to delete
    + immediately, or 0 to cache the dentry. Default is NULL which means to
    + always cache a reachable dentry. d_delete must be constant and
    + idempotent.

    d_release: called when a dentry is really deallocated

    @@ -904,14 +906,11 @@ manipulate dentries:
    the usage count)

    dput: close a handle for a dentry (decrements the usage count). If
    - the usage count drops to 0, the "d_delete" method is called
    - and the dentry is placed on the unused list if the dentry is
    - still in its parents hash list. Putting the dentry on the
    - unused list just means that if the system needs some RAM, it
    - goes through the unused list of dentries and deallocates them.
    - If the dentry has already been unhashed and the usage count
    - drops to 0, in this case the dentry is deallocated after the
    - "d_delete" method is called
    + the usage count drops to 0, and the dentry is still in its
    + parent's hash, the "d_delete" method is called to check whether
    + it should be cached. If it should not be cached, or if the dentry
    + is not hashed, it is deleted. Otherwise cached dentries are put
    + into an LRU list to be reclaimed on memory shortage.

    d_drop: this unhashes a dentry from its parents hash list. A
    subsequent call to dput() will deallocate the dentry if its
    diff --git a/arch/ia64/kernel/perfmon.c b/arch/ia64/kernel/perfmon.c
    index 39e534f..d39d8a5 100644
    --- a/arch/ia64/kernel/perfmon.c
    +++ b/arch/ia64/kernel/perfmon.c
    @@ -2185,7 +2185,7 @@ static const struct file_operations pfm_file_ops = {
    };

    static int
    -pfmfs_delete_dentry(struct dentry *dentry)
    +pfmfs_delete_dentry(const struct dentry *dentry)
    {
    return 1;
    }
    diff --git a/fs/9p/vfs_dentry.c b/fs/9p/vfs_dentry.c
    index cbf4e50..466d2a4 100644
    --- a/fs/9p/vfs_dentry.c
    +++ b/fs/9p/vfs_dentry.c
    @@ -51,7 +51,7 @@
    *
    */

    -static int v9fs_dentry_delete(struct dentry *dentry)
    +static int v9fs_dentry_delete(const struct dentry *dentry)
    {
    P9_DPRINTK(P9_DEBUG_VFS, " dentry: %s (%p)\n", dentry->d_name.name,
    dentry);
    @@ -68,7 +68,7 @@ static int v9fs_dentry_delete(struct dentry *dentry)
    *
    */

    -static int v9fs_cached_dentry_delete(struct dentry *dentry)
    +static int v9fs_cached_dentry_delete(const struct dentry *dentry)
    {
    struct inode *inode = dentry->d_inode;
    P9_DPRINTK(P9_DEBUG_VFS, " dentry: %s (%p)\n", dentry->d_name.name,
    diff --git a/fs/afs/dir.c b/fs/afs/dir.c
    index 5439e1b..2c18cde 100644
    --- a/fs/afs/dir.c
    +++ b/fs/afs/dir.c
    @@ -23,7 +23,7 @@ static struct dentry *afs_lookup(struct inode *dir, struct dentry *dentry,
    static int afs_dir_open(struct inode *inode, struct file *file);
    static int afs_readdir(struct file *file, void *dirent, filldir_t filldir);
    static int afs_d_revalidate(struct dentry *dentry, struct nameidata *nd);
    -static int afs_d_delete(struct dentry *dentry);
    +static int afs_d_delete(const struct dentry *dentry);
    static void afs_d_release(struct dentry *dentry);
    static int afs_lookup_filldir(void *_cookie, const char *name, int nlen,
    loff_t fpos, u64 ino, unsigned dtype);
    @@ -730,7 +730,7 @@ out_bad:
    * - called from dput() when d_count is going to 0.
    * - return 1 to request dentry be unhashed, 0 otherwise
    */
    -static int afs_d_delete(struct dentry *dentry)
    +static int afs_d_delete(const struct dentry *dentry)
    {
    _enter("%s", dentry->d_name.name);

    diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
    index 558cac2..e134e80 100644
    --- a/fs/btrfs/inode.c
    +++ b/fs/btrfs/inode.c
    @@ -4127,7 +4127,7 @@ struct inode *btrfs_lookup_dentry(struct inode *dir, struct dentry *dentry)
    return inode;
    }

    -static int btrfs_dentry_delete(struct dentry *dentry)
    +static int btrfs_dentry_delete(const struct dentry *dentry)
    {
    struct btrfs_root *root;

    diff --git a/fs/coda/dir.c b/fs/coda/dir.c
    index 5d8b355..4cce3b0 100644
    --- a/fs/coda/dir.c
    +++ b/fs/coda/dir.c
    @@ -47,7 +47,7 @@ static int coda_readdir(struct file *file, void *buf, filldir_t filldir);

    /* dentry ops */
    static int coda_dentry_revalidate(struct dentry *de, struct nameidata *nd);
    -static int coda_dentry_delete(struct dentry *);
    +static int coda_dentry_delete(const struct dentry *);

    /* support routines */
    static int coda_venus_readdir(struct file *coda_file, void *buf,
    @@ -577,7 +577,7 @@ out:
    * This is the callback from dput() when d_count is going to 0.
    * We use this to unhash dentries with bad inodes.
    */
    -static int coda_dentry_delete(struct dentry * dentry)
    +static int coda_dentry_delete(const struct dentry * dentry)
    {
    int flags;

    diff --git a/fs/configfs/dir.c b/fs/configfs/dir.c
    index 0b502f8..1001557 100644
    --- a/fs/configfs/dir.c
    +++ b/fs/configfs/dir.c
    @@ -67,7 +67,7 @@ static void configfs_d_iput(struct dentry * dentry,
    * We _must_ delete our dentries on last dput, as the chain-to-parent
    * behavior is required to clear the parents of default_groups.
    */
    -static int configfs_d_delete(struct dentry *dentry)
    +static int configfs_d_delete(const struct dentry *dentry)
    {
    return 1;
    }
    diff --git a/fs/dcache.c b/fs/dcache.c
    index 9d1a59d..14e0564 100644
    --- a/fs/dcache.c
    +++ b/fs/dcache.c
    @@ -446,8 +446,6 @@ static void prune_one_dentry(struct dentry * dentry)
    if (!atomic_dec_and_lock(&dentry->d_count, &dentry->d_lock))
    return;

    - if (dentry->d_op && dentry->d_op->d_delete)
    - dentry->d_op->d_delete(dentry);
    dentry_lru_del(dentry);
    __d_drop(dentry);
    dentry = d_kill(dentry);
    diff --git a/fs/gfs2/dentry.c b/fs/gfs2/dentry.c
    index 6798755..e80fea2 100644
    --- a/fs/gfs2/dentry.c
    +++ b/fs/gfs2/dentry.c
    @@ -106,7 +106,7 @@ static int gfs2_dhash(struct dentry *dentry, struct qstr *str)
    return 0;
    }

    -static int gfs2_dentry_delete(struct dentry *dentry)
    +static int gfs2_dentry_delete(const struct dentry *dentry)
    {
    struct gfs2_inode *ginode;

    diff --git a/fs/hostfs/hostfs_kern.c b/fs/hostfs/hostfs_kern.c
    index 2c0f148..cfe8bc7 100644
    --- a/fs/hostfs/hostfs_kern.c
    +++ b/fs/hostfs/hostfs_kern.c
    @@ -32,7 +32,7 @@ static inline struct hostfs_inode_info *HOSTFS_I(struct inode *inode)

    #define FILE_HOSTFS_I(file) HOSTFS_I((file)->f_path.dentry->d_inode)

    -static int hostfs_d_delete(struct dentry *dentry)
    +static int hostfs_d_delete(const struct dentry *dentry)
    {
    return 1;
    }
    diff --git a/fs/libfs.c b/fs/libfs.c
    index a3accdf..b9d25d8 100644
    --- a/fs/libfs.c
    +++ b/fs/libfs.c
    @@ -37,7 +37,7 @@ int simple_statfs(struct dentry *dentry, struct kstatfs *buf)
    * Retaining negative dentries for an in-memory filesystem just wastes
    * memory and lookup time: arrange for them to be deleted immediately.
    */
    -static int simple_delete_dentry(struct dentry *dentry)
    +static int simple_delete_dentry(const struct dentry *dentry)
    {
    return 1;
    }
    diff --git a/fs/ncpfs/dir.c b/fs/ncpfs/dir.c
    index f22b12e..d6e6453 100644
    --- a/fs/ncpfs/dir.c
    +++ b/fs/ncpfs/dir.c
    @@ -76,7 +76,7 @@ const struct inode_operations ncp_dir_inode_operations =
    static int ncp_lookup_validate(struct dentry *, struct nameidata *);
    static int ncp_hash_dentry(struct dentry *, struct qstr *);
    static int ncp_compare_dentry (struct dentry *, struct qstr *, struct qstr *);
    -static int ncp_delete_dentry(struct dentry *);
    +static int ncp_delete_dentry(const struct dentry *);

    static const struct dentry_operations ncp_dentry_operations =
    {
    @@ -162,7 +162,7 @@ ncp_compare_dentry(struct dentry *dentry, struct qstr *a, struct qstr *b)
    * Closing files can be safely postponed until iput() - it's done there anyway.
    */
    static int
    -ncp_delete_dentry(struct dentry * dentry)
    +ncp_delete_dentry(const struct dentry * dentry)
    {
    struct inode *inode = dentry->d_inode;

    diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
    index 8ea4a41..0f7798a 100644
    --- a/fs/nfs/dir.c
    +++ b/fs/nfs/dir.c
    @@ -1127,7 +1127,7 @@ out_error:
    /*
    * This is called from dput() when d_count is going to 0.
    */
    -static int nfs_dentry_delete(struct dentry *dentry)
    +static int nfs_dentry_delete(const struct dentry *dentry)
    {
    dfprintk(VFS, "NFS: dentry_delete(%s/%s, %x)\n",
    dentry->d_parent->d_name.name, dentry->d_name.name,
    diff --git a/fs/proc/base.c b/fs/proc/base.c
    index f3d02ca..866a41a 100644
    --- a/fs/proc/base.c
    +++ b/fs/proc/base.c
    @@ -1744,7 +1744,7 @@ static int pid_revalidate(struct dentry *dentry, struct nameidata *nd)
    return 0;
    }

    -static int pid_delete_dentry(struct dentry * dentry)
    +static int pid_delete_dentry(const struct dentry * dentry)
    {
    /* Is the task we represent dead?
    * If so, then don't put the dentry on the lru list,
    diff --git a/fs/proc/generic.c b/fs/proc/generic.c
    index dd29f03..1d607be 100644
    --- a/fs/proc/generic.c
    +++ b/fs/proc/generic.c
    @@ -400,7 +400,7 @@ static const struct inode_operations proc_link_inode_operations = {
    * smarter: we could keep a "volatile" flag in the
    * inode to indicate which ones to keep.
    */
    -static int proc_delete_dentry(struct dentry * dentry)
    +static int proc_delete_dentry(const struct dentry * dentry)
    {
    return 1;
    }
    diff --git a/fs/proc/proc_sysctl.c b/fs/proc/proc_sysctl.c
    index b652cb0..a256d77 100644
    --- a/fs/proc/proc_sysctl.c
    +++ b/fs/proc/proc_sysctl.c
    @@ -392,7 +392,7 @@ static int proc_sys_revalidate(struct dentry *dentry, struct nameidata *nd)
    return !PROC_I(dentry->d_inode)->sysctl->unregistering;
    }

    -static int proc_sys_delete(struct dentry *dentry)
    +static int proc_sys_delete(const struct dentry *dentry)
    {
    return !!PROC_I(dentry->d_inode)->sysctl->unregistering;
    }
    diff --git a/fs/sysfs/dir.c b/fs/sysfs/dir.c
    index 7e54bac..27e1102 100644
    --- a/fs/sysfs/dir.c
    +++ b/fs/sysfs/dir.c
    @@ -231,7 +231,7 @@ void release_sysfs_dirent(struct sysfs_dirent * sd)
    goto repeat;
    }

    -static int sysfs_dentry_delete(struct dentry *dentry)
    +static int sysfs_dentry_delete(const struct dentry *dentry)
    {
    struct sysfs_dirent *sd = dentry->d_fsdata;
    return !!(sd->s_flags & SYSFS_FLAG_REMOVED);
    diff --git a/include/linux/dcache.h b/include/linux/dcache.h
    index fff9755..cbfc956 100644
    --- a/include/linux/dcache.h
    +++ b/include/linux/dcache.h
    @@ -133,9 +133,9 @@ enum dentry_d_lock_class

    struct dentry_operations {
    int (*d_revalidate)(struct dentry *, struct nameidata *);
    - int (*d_hash) (struct dentry *, struct qstr *);
    - int (*d_compare) (struct dentry *, struct qstr *, struct qstr *);
    - int (*d_delete)(struct dentry *);
    + int (*d_hash)(struct dentry *, struct qstr *);
    + int (*d_compare)(struct dentry *, struct qstr *, struct qstr *);
    + int (*d_delete)(const struct dentry *);
    void (*d_release)(struct dentry *);
    void (*d_iput)(struct dentry *, struct inode *);
    char *(*d_dname)(struct dentry *, char *, int);
    diff --git a/net/sunrpc/rpc_pipe.c b/net/sunrpc/rpc_pipe.c
    index 10a17a3..a0dc1a8 100644
    --- a/net/sunrpc/rpc_pipe.c
    +++ b/net/sunrpc/rpc_pipe.c
    @@ -430,7 +430,7 @@ void rpc_put_mount(void)
    }
    EXPORT_SYMBOL_GPL(rpc_put_mount);

    -static int rpc_delete_dentry(struct dentry *dentry)
    +static int rpc_delete_dentry(const struct dentry *dentry)
    {
    return 1;
    }
    --
    1.7.1


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