Commit 4b936885 authored by Nick Piggin's avatar Nick Piggin
Browse files

fs: improve scalability of pseudo filesystems 



Regardless of how much we possibly try to scale dcache, there is likely
always going to be some fundamental contention when adding or removing children
under the same parent. Pseudo filesystems do not seem need to have connected
dentries because by definition they are disconnected.

Signed-off-by: default avatarNick Piggin <npiggin@kernel.dk>
parent 873feea0

fs/anon_inodes.c

+1 −1
Original line number Diff line number Diff line
@@ -102,7 +102,7 @@ struct file *anon_inode_getfile(const char *name, 
	this.name = name;

	this.len = strlen(name);

	this.hash = 0;

	path.dentry = d_alloc(anon_inode_mnt->mnt_sb->s_root, &this);

	path.dentry = d_alloc_pseudo(anon_inode_mnt->mnt_sb, &this);

	if (!path.dentry)

		goto err_module;

fs/dcache.c

+12 −0
Original line number Diff line number Diff line
@@ -1330,6 +1330,18 @@ struct dentry *d_alloc(struct dentry * parent, const struct qstr *name) 
}

EXPORT_SYMBOL(d_alloc);



struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name)

{

	struct dentry *dentry = d_alloc(NULL, name);

	if (dentry) {

		dentry->d_sb = sb;

		dentry->d_parent = dentry;

		dentry->d_flags |= DCACHE_DISCONNECTED;

	}

	return dentry;

}

EXPORT_SYMBOL(d_alloc_pseudo);



struct dentry *d_alloc_name(struct dentry *parent, const char *name)

{

	struct qstr q;

fs/pipe.c

+1 −1
Original line number Diff line number Diff line
@@ -999,7 +999,7 @@ struct file *create_write_pipe(int flags) 
		goto err;



	err = -ENOMEM;

	path.dentry = d_alloc(pipe_mnt->mnt_sb->s_root, &name);

	path.dentry = d_alloc_pseudo(pipe_mnt->mnt_sb, &name);

	if (!path.dentry)

		goto err_inode;

	path.mnt = mntget(pipe_mnt);

include/linux/dcache.h

+1 −0
Original line number Diff line number Diff line
@@ -211,6 +211,7 @@ extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op 


/* allocate/de-allocate */

extern struct dentry * d_alloc(struct dentry *, const struct qstr *);

extern struct dentry * d_alloc_pseudo(struct super_block *, const struct qstr *);

extern struct dentry * d_splice_alias(struct inode *, struct dentry *);

extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);

extern struct dentry * d_obtain_alias(struct inode *);

net/socket.c

+1 −1
Original line number Diff line number Diff line
@@ -361,7 +361,7 @@ static int sock_alloc_file(struct socket *sock, struct file **f, int flags) 
	if (unlikely(fd < 0))

		return fd;



	path.dentry = d_alloc(sock_mnt->mnt_sb->s_root, &name);

	path.dentry = d_alloc_pseudo(sock_mnt->mnt_sb, &name);

	if (unlikely(!path.dentry)) {

		put_unused_fd(fd);

		return -ENOMEM;

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