The patch titled
net: don't insert socket dentries into dentry_hashtable
has been added to the -mm tree. Its filename is
net-dont-insert-socket-dentries-into-dentry_hashtable.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: net: don't insert socket dentries into dentry_hashtable
From: Eric Dumazet <dada1@xxxxxxxxxxxxx>
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@xxxxxxxxxxxxx>
Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
net/socket.c | 19 ++++++++++++++++---
1 files changed, 16 insertions(+), 3 deletions(-)
diff -puN net/socket.c~net-dont-insert-socket-dentries-into-dentry_hashtable net/socket.c
--- a/net/socket.c~net-dont-insert-socket-dentries-into-dentry_hashtable
+++ a/net/socket.c
@@ -305,7 +305,14 @@ static struct file_system_type sock_fs_t
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
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;
_
Patches currently in -mm which might be from dada1@xxxxxxxxxxxxx are
git-net.patch
rcu-add-a-prefetch-in-rcu_do_batch.patch
dont-insert-pipe-dentries-into-dentry_hashtable.patch
dcache-avoid-rcu-for-never-hashed-dentries.patch
net-dont-insert-socket-dentries-into-dentry_hashtable.patch
-
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