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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: Nick Piggin <npiggin@kernel.dk>
This commit is contained in:
Nick Piggin 2011-01-07 17:50:07 +11:00
parent 873feea09e
commit 4b936885ab
5 changed files with 16 additions and 3 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
fs/anon_inodes.c
View File

@ -102,7 +102,7 @@ struct file *anon_inode_getfile(const char *name,
this.name = name; this.name = name;
this.len = strlen(name); this.len = strlen(name);
this.hash = 0; 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) if (!path.dentry)
goto err_module; goto err_module;

12
fs/dcache.c
View File

@ -1330,6 +1330,18 @@ struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
} }
EXPORT_SYMBOL(d_alloc); 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 dentry *d_alloc_name(struct dentry *parent, const char *name)
{ {
struct qstr q; struct qstr q;

2
fs/pipe.c
View File

@ -999,7 +999,7 @@ struct file *create_write_pipe(int flags)
goto err; goto err;
err = -ENOMEM; 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) if (!path.dentry)
goto err_inode; goto err_inode;
path.mnt = mntget(pipe_mnt); path.mnt = mntget(pipe_mnt);

1
include/linux/dcache.h
View File

@ -211,6 +211,7 @@ extern void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op
/* allocate/de-allocate */ /* allocate/de-allocate */
extern struct dentry * d_alloc(struct dentry *, const struct qstr *); 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_splice_alias(struct inode *, struct dentry *);
extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *); extern struct dentry * d_add_ci(struct dentry *, struct inode *, struct qstr *);
extern struct dentry * d_obtain_alias(struct inode *); extern struct dentry * d_obtain_alias(struct inode *);

2
net/socket.c
View File

@ -361,7 +361,7 @@ static int sock_alloc_file(struct socket *sock, struct file **f, int flags)
if (unlikely(fd < 0)) if (unlikely(fd < 0))
return fd; 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)) { if (unlikely(!path.dentry)) {
put_unused_fd(fd); put_unused_fd(fd);
return -ENOMEM; return -ENOMEM;