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authorEric Dumazet <dada1@cosmosbay.com>2006-12-06 20:38:49 -0800
committerLinus Torvalds <torvalds@woody.osdl.org>2006-12-07 08:39:41 -0800
commit304e61e6fbadec586dfe002b535f169a04248e49 (patch)
treeb70c8ec7ca6b538b5d02f3c5372a35268643a5bf /net/socket.c
parentb3423415fbc2e5461605826317da1c8dbbf21f97 (diff)
downloadlwn-304e61e6fbadec586dfe002b535f169a04248e49.tar.gz
lwn-304e61e6fbadec586dfe002b535f169a04248e49.zip
[PATCH] net: don't insert socket dentries into dentry_hashtable
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>
Diffstat (limited to 'net/socket.c')
-rw-r--r--net/socket.c19
1 files changed, 16 insertions, 3 deletions
diff --git a/net/socket.c b/net/socket.c
index 43eff489c878..29ea1de43ecb 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -305,7 +305,14 @@ static struct file_system_type sock_fs_type = {
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 = {
.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.name = name;
- this.hash = SOCK_INODE(sock)->i_ino;
+ this.hash = 0;
file->f_dentry = d_alloc(sock_mnt->mnt_sb->s_root, &this);
if (unlikely(!file->f_dentry))
return -ENOMEM;
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_mapping = file->f_dentry->d_inode->i_mapping;