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    Subject[PATCH 17/73] tmpfs: Add fallthru support [ver #2]
    Date
    From: Valerie Aurora <vaurora@redhat.com>

    Add support for fallthru directory entries to tmpfs.

    Original-author: Valerie Aurora <vaurora@redhat.com>
    Signed-off-by: David Howells <dhowells@redhat.com>
    ---

    fs/dcache.c | 4 +++-
    fs/libfs.c | 16 ++++++++++++---
    mm/shmem.c | 64 ++++++++++++++++++++++++++++++++++++++++++++++++++++-------
    3 files changed, 72 insertions(+), 12 deletions(-)

    diff --git a/fs/dcache.c b/fs/dcache.c
    index b1ce8d1..238684a 100644
    --- a/fs/dcache.c
    +++ b/fs/dcache.c
    @@ -2896,7 +2896,9 @@ resume:
    * can evict it.
    */
    if (d_unhashed(dentry) ||
    - (!dentry->d_inode && !d_is_whiteout(dentry))) {
    + (!dentry->d_inode &&
    + !d_is_whiteout(dentry) &&
    + !d_is_fallthru(dentry))) {
    spin_unlock(&dentry->d_lock);
    continue;
    }
    diff --git a/fs/libfs.c b/fs/libfs.c
    index 38eb46d..43f1ac2 100644
    --- a/fs/libfs.c
    +++ b/fs/libfs.c
    @@ -141,6 +141,7 @@ 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;
    + char d_type;
    int i = filp->f_pos;

    switch (i) {
    @@ -167,17 +168,26 @@ int dcache_readdir(struct file * filp, void * dirent, filldir_t filldir)
    struct dentry *next;
    next = list_entry(p, struct dentry, d_u.d_child);
    spin_lock_nested(&next->d_lock, DENTRY_D_LOCK_NESTED);
    - if (!simple_positive(next)) {
    + if (d_unhashed(next) ||
    + (!next->d_inode && !d_is_fallthru(next))) {
    spin_unlock(&next->d_lock);
    continue;
    }

    spin_unlock(&next->d_lock);
    spin_unlock(&dentry->d_lock);
    + if (d_is_fallthru(next)) {
    + /* XXX placeholder until generic_readdir_fallthru() arrives */
    + ino = 1;
    + d_type = DT_UNKNOWN;
    + } else {
    + ino = next->d_inode->i_ino;
    + d_type = dt_type(next->d_inode);
    + }
    +
    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(&dentry->d_lock);
    spin_lock_nested(&next->d_lock, DENTRY_D_LOCK_NESTED);
    diff --git a/mm/shmem.c b/mm/shmem.c
    index ca0bd30..bfd9ac8 100644
    --- a/mm/shmem.c
    +++ b/mm/shmem.c
    @@ -1481,8 +1481,7 @@ 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)
    @@ -1513,8 +1512,10 @@ 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);
    @@ -1531,6 +1532,48 @@ 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)) {
    @@ -1538,14 +1581,15 @@ 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..
    @@ -1627,7 +1671,8 @@ 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) {
    @@ -2347,8 +2392,10 @@ int shmem_fill_super(struct super_block *sb, void *data, int silent)
    sb->s_root = root;

    #ifdef CONFIG_TMPFS
    - if (!(sb->s_flags & MS_NOUSER))
    + if (!(sb->s_flags & MS_NOUSER)) {
    sb->s_flags |= MS_WHITEOUT;
    + sb->s_flags |= MS_FALLTHRU;
    + }
    #endif

    return 0;
    @@ -2451,6 +2498,7 @@ 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_XATTR
    .setxattr = shmem_setxattr,


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