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    Subject[PATCH 16/38] fallthru: tmpfs fallthru support
    Date
    Add support for fallthru directory entries to tmpfs

    XXX - Makes up inode number for dirent

    Signed-off-by: Valerie Aurora <vaurora@redhat.com>
    ---
    fs/dcache.c | 3 +-
    fs/libfs.c | 21 +++++++++++++++++--
    mm/shmem.c | 60 ++++++++++++++++++++++++++++++++++++++++++++++++++++------
    3 files changed, 73 insertions(+), 11 deletions(-)

    diff --git a/fs/dcache.c b/fs/dcache.c
    index b76f9e4..1575af4 100644
    --- a/fs/dcache.c
    +++ b/fs/dcache.c
    @@ -2240,7 +2240,8 @@ resume:
    * we can evict it.
    */
    if (d_unhashed(dentry)||(!dentry->d_inode &&
    - !d_is_whiteout(dentry)))
    + !d_is_whiteout(dentry) &&
    + !d_is_fallthru(dentry)))
    continue;
    if (!list_empty(&dentry->d_subdirs)) {
    this_parent = dentry;
    diff --git a/fs/libfs.c b/fs/libfs.c
    index ea9a6cc..2b28ca9 100644
    --- a/fs/libfs.c
    +++ b/fs/libfs.c
    @@ -134,6 +134,7 @@ int dcache_readdir(struct file * filp, void * dirent, filldir_t filldir)
    struct dentry *cursor = filp->private_data;
    struct list_head *p, *q = &cursor->d_u.d_child;
    ino_t ino;
    + int d_type;
    int i = filp->f_pos;

    switch (i) {
    @@ -159,14 +160,28 @@ int dcache_readdir(struct file * filp, void * dirent, filldir_t filldir)
    for (p=q->next; p != &dentry->d_subdirs; p=p->next) {
    struct dentry *next;
    next = list_entry(p, struct dentry, d_u.d_child);
    - if (d_unhashed(next) || !next->d_inode)
    + if (d_unhashed(next) || (!next->d_inode && !d_is_fallthru(next)))
    continue;

    + if (d_is_fallthru(next)) {
    + /* XXX We don't know the inode
    + * number of the directory
    + * entry in the underlying
    + * file system. Should look
    + * it up, either on fallthru
    + * creation at first readdir
    + * or now at filldir time. */
    + ino = 123; /* Made up ino */
    + d_type = DT_UNKNOWN;
    + } else {
    + ino = next->d_inode->i_ino;
    + d_type = dt_type(next->d_inode);
    + }
    +
    spin_unlock(&dcache_lock);
    if (filldir(dirent, next->d_name.name,
    next->d_name.len, filp->f_pos,
    - next->d_inode->i_ino,
    - dt_type(next->d_inode)) < 0)
    + ino, d_type) < 0)
    return 0;
    spin_lock(&dcache_lock);
    /* next is still alive */
    diff --git a/mm/shmem.c b/mm/shmem.c
    index c58ecf4..163957b 100644
    --- a/mm/shmem.c
    +++ b/mm/shmem.c
    @@ -1809,8 +1809,7 @@ static int shmem_rmdir(struct inode *dir, struct dentry *dentry);
    static int shmem_unlink(struct inode *dir, struct dentry *dentry);

    /*
    - * This is the whiteout support for tmpfs. It uses one singleton whiteout
    - * inode per superblock thus it is very similar to shmem_link().
    + * Create a dentry to signify a whiteout.
    */
    static int shmem_whiteout(struct inode *dir, struct dentry *old_dentry,
    struct dentry *new_dentry)
    @@ -1841,8 +1840,10 @@ static int shmem_whiteout(struct inode *dir, struct dentry *old_dentry,
    spin_unlock(&sbinfo->stat_lock);
    }

    - if (old_dentry->d_inode) {
    - if (S_ISDIR(old_dentry->d_inode->i_mode))
    + if (old_dentry->d_inode || d_is_fallthru(old_dentry)) {
    + /* A fallthru for a dir is treated like a regular link */
    + if (old_dentry->d_inode &&
    + S_ISDIR(old_dentry->d_inode->i_mode))
    shmem_rmdir(dir, old_dentry);
    else
    shmem_unlink(dir, old_dentry);
    @@ -1859,6 +1860,48 @@ static int shmem_whiteout(struct inode *dir, struct dentry *old_dentry,
    }

    static void shmem_d_instantiate(struct inode *dir, struct dentry *dentry,
    + struct inode *inode);
    +
    +/*
    + * Create a dentry to signify a fallthru. A fallthru in tmpfs is the
    + * logical equivalent of an in-kernel readdir() cache. It can't be
    + * deleted until the file system is unmounted.
    + */
    +static int shmem_fallthru(struct inode *dir, struct dentry *dentry)
    +{
    + struct shmem_sb_info *sbinfo = SHMEM_SB(dir->i_sb);
    +
    + /* FIXME: this is stupid */
    + if (!(dir->i_sb->s_flags & MS_WHITEOUT))
    + return -EPERM;
    +
    + if (dentry->d_inode || d_is_fallthru(dentry) || d_is_whiteout(dentry))
    + return -EEXIST;
    +
    + /*
    + * Each new link needs a new dentry, pinning lowmem, and tmpfs
    + * dentries cannot be pruned until they are unlinked.
    + */
    + if (sbinfo->max_inodes) {
    + spin_lock(&sbinfo->stat_lock);
    + if (!sbinfo->free_inodes) {
    + spin_unlock(&sbinfo->stat_lock);
    + return -ENOSPC;
    + }
    + sbinfo->free_inodes--;
    + spin_unlock(&sbinfo->stat_lock);
    + }
    +
    + shmem_d_instantiate(dir, dentry, NULL);
    + dir->i_ctime = dir->i_mtime = CURRENT_TIME;
    +
    + spin_lock(&dentry->d_lock);
    + dentry->d_flags |= DCACHE_FALLTHRU;
    + spin_unlock(&dentry->d_lock);
    + return 0;
    +}
    +
    +static void shmem_d_instantiate(struct inode *dir, struct dentry *dentry,
    struct inode *inode)
    {
    if (d_is_whiteout(dentry)) {
    @@ -1866,14 +1909,15 @@ static void shmem_d_instantiate(struct inode *dir, struct dentry *dentry,
    shmem_free_inode(dir->i_sb);
    if (S_ISDIR(inode->i_mode))
    inode->i_mode |= S_OPAQUE;
    + } else if (d_is_fallthru(dentry)) {
    + shmem_free_inode(dir->i_sb);
    } else {
    /* New dentry */
    dir->i_size += BOGO_DIRENT_SIZE;
    dget(dentry); /* Extra count - pin the dentry in core */
    }
    - /* Will clear DCACHE_WHITEOUT flag */
    + /* Will clear DCACHE_WHITEOUT and DCACHE_FALLTHRU flags */
    d_instantiate(dentry, inode);
    -
    }
    /*
    * File creation. Allocate an inode, and we're done..
    @@ -1962,7 +2006,8 @@ static int shmem_unlink(struct inode *dir, struct dentry *dentry)
    {
    struct inode *inode = dentry->d_inode;

    - if (d_is_whiteout(dentry) || (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode)))
    + if (d_is_whiteout(dentry) || d_is_fallthru(dentry) ||
    + (inode->i_nlink > 1 && !S_ISDIR(inode->i_mode)))
    shmem_free_inode(dir->i_sb);

    if (inode) {
    @@ -2596,6 +2641,7 @@ static const struct inode_operations shmem_dir_inode_operations = {
    .mknod = shmem_mknod,
    .rename = shmem_rename,
    .whiteout = shmem_whiteout,
    + .fallthru = shmem_fallthru,
    #endif
    #ifdef CONFIG_TMPFS_POSIX_ACL
    .setattr = shmem_notify_change,
    --
    1.6.3.3


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