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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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