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[PATCH] net: don't insert socket dentries into dentry_hashtable

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We currently insert socket dentries into the global dentry hashtable.  This
is suboptimal because there is currently no way these entries can be used
for a lookup().  (/proc/xxx/fd/xxx uses a different mechanism).  Inserting
them in dentry hashtable slows dcache lookups.

To let __dpath() still work correctly (ie not adding a " (deleted)") after
dentry name, we do :

- Right after d_alloc(), pretend they are hashed by clearing the
  DCACHE_UNHASHED bit.

- Call d_instantiate() instead of d_add() : dentry is not inserted in
  hash table.

  __dpath() & friends work as intended during dentry lifetime.

- At dismantle time, once dput() must clear the dentry, setting again
  DCACHE_UNHASHED bit inside the custom d_delete() function provided by
  socket code, so that dput() can just kill_it.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Acked-by: "David S. Miller" <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Eric Dumazet 2006-12-06 20:38:49 -08:00 committed by Linus Torvalds
parent b3423415fb
commit 304e61e6fb
1 changed files with 16 additions and 3 deletions
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19
net/socket.c
View file

@ -305,7 +305,14 @@ static struct file_system_type sock_fs_type = {
static int sockfs_delete_dentry(struct dentry *dentry) static int sockfs_delete_dentry(struct dentry *dentry)
{ {
return 1; /*
* At creation time, we pretended this dentry was hashed
* (by clearing DCACHE_UNHASHED bit in d_flags)
* At delete time, we restore the truth : not hashed.
* (so that dput() can proceed correctly)
*/
dentry->d_flags |= DCACHE_UNHASHED;
return 0;
} }
static struct dentry_operations sockfs_dentry_operations = { static struct dentry_operations sockfs_dentry_operations = {
.d_delete = sockfs_delete_dentry, .d_delete = sockfs_delete_dentry,
@ -353,14 +360,20 @@ static int sock_attach_fd(struct socket *sock, struct file *file)
this.len = sprintf(name, "[%lu]", SOCK_INODE(sock)->i_ino); this.len = sprintf(name, "[%lu]", SOCK_INODE(sock)->i_ino);
this.name = name; this.name = name;
this.hash = SOCK_INODE(sock)->i_ino; this.hash = 0;
file->f_dentry = d_alloc(sock_mnt->mnt_sb->s_root, &this); file->f_dentry = d_alloc(sock_mnt->mnt_sb->s_root, &this);
if (unlikely(!file->f_dentry)) if (unlikely(!file->f_dentry))
return -ENOMEM; return -ENOMEM;
file->f_dentry->d_op = &sockfs_dentry_operations; file->f_dentry->d_op = &sockfs_dentry_operations;
d_add(file->f_dentry, SOCK_INODE(sock)); /*
* We dont want to push this dentry into global dentry hash table.
* We pretend dentry is already hashed, by unsetting DCACHE_UNHASHED
* This permits a working /proc/$pid/fd/XXX on sockets
*/
file->f_dentry->d_flags &= ~DCACHE_UNHASHED;
d_instantiate(file->f_dentry, SOCK_INODE(sock));
file->f_vfsmnt = mntget(sock_mnt); file->f_vfsmnt = mntget(sock_mnt);
file->f_mapping = file->f_dentry->d_inode->i_mapping; file->f_mapping = file->f_dentry->d_inode->i_mapping;