forked from luck/tmp_suning_uos_patched
VFS: delay the dentry name generation on sockets and pipes
1) Introduces a new method in 'struct dentry_operations'. This method called d_dname() might be called from d_path() to build a pathname for special filesystems. It is called without locks. Future patches (if we succeed in having one common dentry for all pipes/sockets) may need to change prototype of this method, but we now use : char *d_dname(struct dentry *dentry, char *buffer, int buflen); 2) Adds a dynamic_dname() helper function that eases d_dname() implementations 3) Defines d_dname method for sockets : No more sprintf() at socket creation. This is delayed up to the moment someone does an access to /proc/pid/fd/... 4) Defines d_dname method for pipes : No more sprintf() at pipe creation. This is delayed up to the moment someone does an access to /proc/pid/fd/... A benchmark consisting of 1.000.000 calls to pipe()/close()/close() gives a *nice* speedup on my Pentium(M) 1.6 Ghz : 3.090 s instead of 3.450 s Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> Acked-by: Christoph Hellwig <hch@infradead.org> Acked-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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2793274298
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@ -15,6 +15,7 @@ prototypes:
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int (*d_delete)(struct dentry *);
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void (*d_release)(struct dentry *);
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void (*d_iput)(struct dentry *, struct inode *);
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char *(*d_dname)((struct dentry *dentry, char *buffer, int buflen);
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locking rules:
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none have BKL
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@ -25,6 +26,7 @@ d_compare: no yes no no
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d_delete: yes no yes no
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d_release: no no no yes
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d_iput: no no no yes
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d_dname: no no no no
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--------------------------- inode_operations ---------------------------
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prototypes:
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@ -827,7 +827,7 @@ This describes how a filesystem can overload the standard dentry
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operations. Dentries and the dcache are the domain of the VFS and the
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individual filesystem implementations. Device drivers have no business
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here. These methods may be set to NULL, as they are either optional or
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the VFS uses a default. As of kernel 2.6.13, the following members are
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the VFS uses a default. As of kernel 2.6.22, the following members are
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defined:
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struct dentry_operations {
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@ -837,6 +837,7 @@ struct dentry_operations {
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int (*d_delete)(struct dentry *);
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void (*d_release)(struct dentry *);
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void (*d_iput)(struct dentry *, struct inode *);
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char *(*d_dname)(struct dentry *, char *, int);
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};
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d_revalidate: called when the VFS needs to revalidate a dentry. This
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@ -859,6 +860,26 @@ struct dentry_operations {
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VFS calls iput(). If you define this method, you must call
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iput() yourself
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d_dname: called when the pathname of a dentry should be generated.
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Usefull for some pseudo filesystems (sockfs, pipefs, ...) to delay
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pathname generation. (Instead of doing it when dentry is created,
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its done only when the path is needed.). Real filesystems probably
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dont want to use it, because their dentries are present in global
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dcache hash, so their hash should be an invariant. As no lock is
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held, d_dname() should not try to modify the dentry itself, unless
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appropriate SMP safety is used. CAUTION : d_path() logic is quite
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tricky. The correct way to return for example "Hello" is to put it
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at the end of the buffer, and returns a pointer to the first char.
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dynamic_dname() helper function is provided to take care of this.
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Example :
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static char *pipefs_dname(struct dentry *dent, char *buffer, int buflen)
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{
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return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
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dentry->d_inode->i_ino);
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}
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Each dentry has a pointer to its parent dentry, as well as a hash list
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of child dentries. Child dentries are basically like files in a
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directory.
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31
fs/dcache.c
31
fs/dcache.c
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@ -1853,6 +1853,16 @@ char * d_path(struct dentry *dentry, struct vfsmount *vfsmnt,
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struct vfsmount *rootmnt;
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struct dentry *root;
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/*
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* We have various synthetic filesystems that never get mounted. On
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* these filesystems dentries are never used for lookup purposes, and
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* thus don't need to be hashed. They also don't need a name until a
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* user wants to identify the object in /proc/pid/fd/. The little hack
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* below allows us to generate a name for these objects on demand:
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*/
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if (dentry->d_op && dentry->d_op->d_dname)
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return dentry->d_op->d_dname(dentry, buf, buflen);
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read_lock(¤t->fs->lock);
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rootmnt = mntget(current->fs->rootmnt);
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root = dget(current->fs->root);
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@ -1865,6 +1875,27 @@ char * d_path(struct dentry *dentry, struct vfsmount *vfsmnt,
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return res;
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}
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/*
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* Helper function for dentry_operations.d_dname() members
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*/
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char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen,
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const char *fmt, ...)
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{
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va_list args;
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char temp[64];
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int sz;
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va_start(args, fmt);
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sz = vsnprintf(temp, sizeof(temp), fmt, args) + 1;
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va_end(args);
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if (sz > sizeof(temp) || sz > buflen)
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return ERR_PTR(-ENAMETOOLONG);
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buffer += buflen - sz;
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return memcpy(buffer, temp, sz);
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}
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/*
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* NOTE! The user-level library version returns a
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* character pointer. The kernel system call just
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18
fs/pipe.c
18
fs/pipe.c
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@ -841,8 +841,18 @@ static int pipefs_delete_dentry(struct dentry *dentry)
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return 0;
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}
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/*
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* pipefs_dname() is called from d_path().
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*/
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static char *pipefs_dname(struct dentry *dentry, char *buffer, int buflen)
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{
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return dynamic_dname(dentry, buffer, buflen, "pipe:[%lu]",
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dentry->d_inode->i_ino);
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}
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static struct dentry_operations pipefs_dentry_operations = {
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.d_delete = pipefs_delete_dentry,
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.d_dname = pipefs_dname,
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};
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static struct inode * get_pipe_inode(void)
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@ -888,8 +898,7 @@ struct file *create_write_pipe(void)
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struct inode *inode;
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struct file *f;
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struct dentry *dentry;
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char name[32];
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struct qstr this;
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struct qstr name = { .name = "" };
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f = get_empty_filp();
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if (!f)
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@ -899,11 +908,8 @@ struct file *create_write_pipe(void)
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if (!inode)
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goto err_file;
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this.len = sprintf(name, "[%lu]", inode->i_ino);
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this.name = name;
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this.hash = 0;
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err = -ENOMEM;
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dentry = d_alloc(pipe_mnt->mnt_sb->s_root, &this);
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dentry = d_alloc(pipe_mnt->mnt_sb->s_root, &name);
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if (!dentry)
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goto err_inode;
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@ -133,6 +133,7 @@ struct dentry_operations {
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int (*d_delete)(struct dentry *);
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void (*d_release)(struct dentry *);
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void (*d_iput)(struct dentry *, struct inode *);
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char *(*d_dname)(struct dentry *, char *, int);
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};
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/* the dentry parameter passed to d_hash and d_compare is the parent
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@ -293,6 +294,11 @@ extern struct dentry * d_hash_and_lookup(struct dentry *, struct qstr *);
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/* validate "insecure" dentry pointer */
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extern int d_validate(struct dentry *, struct dentry *);
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/*
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* helper function for dentry_operations.d_dname() members
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*/
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extern char *dynamic_dname(struct dentry *, char *, int, const char *, ...);
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extern char * d_path(struct dentry *, struct vfsmount *, char *, int);
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/* Allocation counts.. */
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20
net/socket.c
20
net/socket.c
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@ -313,8 +313,19 @@ static int sockfs_delete_dentry(struct dentry *dentry)
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dentry->d_flags |= DCACHE_UNHASHED;
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return 0;
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}
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/*
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* sockfs_dname() is called from d_path().
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*/
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static char *sockfs_dname(struct dentry *dentry, char *buffer, int buflen)
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{
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return dynamic_dname(dentry, buffer, buflen, "socket:[%lu]",
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dentry->d_inode->i_ino);
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}
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static struct dentry_operations sockfs_dentry_operations = {
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.d_delete = sockfs_delete_dentry,
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.d_dname = sockfs_dname,
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};
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/*
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static int sock_attach_fd(struct socket *sock, struct file *file)
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{
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struct qstr this;
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char name[32];
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struct qstr name = { .name = "" };
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this.len = sprintf(name, "[%lu]", SOCK_INODE(sock)->i_ino);
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this.name = name;
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this.hash = 0;
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file->f_path.dentry = d_alloc(sock_mnt->mnt_sb->s_root, &this);
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file->f_path.dentry = d_alloc(sock_mnt->mnt_sb->s_root, &name);
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if (unlikely(!file->f_path.dentry))
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return -ENOMEM;
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