[PATCH] fix integer overflow in H-TCP congestion control

[PATCH] fix integer overflow in H-TCP congestion control

[Gavin McCullagh]

When using H-TCP with a single flow on a 500Mbit connection (or less
actually), alpha can exceed 65000, so alpha needs to be a u32.

Signed-off-by: Gavin McCullagh <gavin.mccullagh@nuim.ie>
Signed-off-by: Doug Leith <doug.leith@nuim.ie>


diff --git a/net/ipv4/tcp_htcp.c b/net/ipv4/tcp_htcp.c
index 6edfe5e..8072b6d 100644
--- a/net/ipv4/tcp_htcp.c
+++ b/net/ipv4/tcp_htcp.c
@@ -23,7 +23,7 @@ module_param(use_bandwidth_switch, int, 
 MODULE_PARM_DESC(use_bandwidth_switch, "turn on/off bandwidth switcher");
 
 struct htcp {
-       u16     alpha;          /* Fixed point arith, << 7 */
+       u32     alpha;          /* Fixed point arith, << 7 */
        u8      beta;           /* Fixed point arith, << 7 */
        u8      modeswitch;     /* Delay modeswitch until we had at least one congestion event */
        u32     last_cong;      /* Time since last congestion event end */

Re: [PATCH] fix integer overflow in H-TCP congestion control

[David Miller]

Your patch doesn't apply, your email client turned the tab
characters in the patch into spaces.

Please fix and resubmit, thank you.

Re: [PATCH] fix integer overflow in H-TCP congestion control

[Gavin McCullagh]

When using H-TCP with a single flow on a 500Mbit connection (or less
actually), alpha can exceed 65000, so alpha needs to be a u32.

Signed-off-by: Gavin McCullagh <gavin.mccullagh@nuim.ie>
Signed-off-by: Doug Leith <doug.leith@nuim.ie>


diff --git a/net/ipv4/tcp_htcp.c b/net/ipv4/tcp_htcp.c
index 6edfe5e..8072b6d 100644
--- a/net/ipv4/tcp_htcp.c
+++ b/net/ipv4/tcp_htcp.c
@@ -23,7 +23,7 @@ module_param(use_bandwidth_switch, int, 
 MODULE_PARM_DESC(use_bandwidth_switch, "turn on/off bandwidth switcher");
 
 struct htcp {
-	u16	alpha;		/* Fixed point arith, << 7 */
+	u32	alpha;		/* Fixed point arith, << 7 */
 	u8	beta;           /* Fixed point arith, << 7 */
 	u8	modeswitch;     /* Delay modeswitch until we had at least one congestion event */
 	u32	last_cong;	/* Time since last congestion event end */

Re: [PATCH] fix integer overflow in H-TCP congestion control

[David Miller]

From: Gavin McCullagh <gavin.mccullagh@nuim.ie>
Date: Wed, 25 Oct 2006 09:47:26 +0100

> When using H-TCP with a single flow on a 500Mbit connection (or less
> actually), alpha can exceed 65000, so alpha needs to be a u32.
> 
> Signed-off-by: Gavin McCullagh <gavin.mccullagh@nuim.ie>
> Signed-off-by: Doug Leith <doug.leith@nuim.ie>

Applied, thank you.

[RFC, PATCH] dont insert sockets/pipes dentries into dentry_hashtable.

[Eric Dumazet]

[-- Attachment #1: Type: text/plain, Size: 1629 bytes --]

Hi David

Here is the patch I cooked after our mail exchange. (was [RFC] Any strong 
reason why socket dentries are hashed in global dentry_hashtable )

If necessary, I could split this patch in 4 elementary patches. I chose to 
sent it as one patch for initial discussion.

[RFC, PATCH] dont insert sockets/pipes dentries into dentry_hashtable.

We currently insert sockets/pipes dentries into the global dentry hashtable.
This is *useless* because there is currently no way these entries can be used 
for a lookup(). (/proc/xxx/fd/xxx uses a different mechanism)

Machines with a lot of sockets/pipes might suffer from longer chains in dentry 
hashtable.

The goals of this patch are :

[0] No more insertion in hashtable of sockets/pipes dentries.

[1] Introduction of a DENTRY_DELETED flag, that can distinguish dentries that 
were deleted and others in d_path(). (previous code was using d_unhashed())

[2] Small optimization to bypass RCU freeing in d_free() for dentries that 
were never hashed (like sockets and pipes). Such dentries dont have to wait a 
RCU grace period.

[3] Plug socket code to use d_instantiate() instead of d_hash()
   (No more need for a private d_delete function, and dentry_operations)

[4] Plug pipe code to use d_instantiate() instead of d_hash()
   (No more need for a private d_delete function, and dentry_operations)

Another step would be to eliminate dentries for sockets/pipes, but that's 
another story. (Or at least allocate them from a separate kmem_cache_t as 
they are not reclaimable, and they might be smaller than a full dentry)

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>

[-- Attachment #2: dcache.patch --]
[-- Type: text/plain, Size: 3652 bytes --]

--- linux-2.6.19-rc4/include/linux/dcache.h	2006-10-31 17:38:09.000000000 +0100
+++ linux-2.6.19-rc4-ed/include/linux/dcache.h	2006-10-31 17:39:15.000000000 +0100
@@ -175,6 +175,7 @@
 #define DCACHE_UNHASHED		0x0010	
 
 #define DCACHE_INOTIFY_PARENT_WATCHED	0x0020 /* Parent inode is watched */
+#define DCACHE_DELETED		0x0040 /* dentry was deleted */
 
 extern spinlock_t dcache_lock;
 
--- linux-2.6.19-rc4/fs/dcache.c	2006-10-31 17:39:25.000000000 +0100
+++ linux-2.6.19-rc4-ed/fs/dcache.c	2006-10-31 18:37:26.000000000 +0100
@@ -68,15 +68,19 @@
 	.age_limit = 45,
 };
 
-static void d_callback(struct rcu_head *head)
+static void __d_free(struct dentry *dentry)
 {
-	struct dentry * dentry = container_of(head, struct dentry, d_u.d_rcu);
-
 	if (dname_external(dentry))
 		kfree(dentry->d_name.name);
 	kmem_cache_free(dentry_cache, dentry); 
 }
 
+static void d_callback(struct rcu_head *head)
+{
+	struct dentry * dentry = container_of(head, struct dentry, d_u.d_rcu);
+	__d_free(dentry);
+}
+
 /*
  * no dcache_lock, please.  The caller must decrement dentry_stat.nr_dentry
  * inside dcache_lock.
@@ -85,7 +89,11 @@
 {
 	if (dentry->d_op && dentry->d_op->d_release)
 		dentry->d_op->d_release(dentry);
- 	call_rcu(&dentry->d_u.d_rcu, d_callback);
+	/* if dentry was never inserted into hash, immediate free is OK */
+	if (dentry->d_hash.pprev == NULL)
+		__d_free(dentry);
+	else
+		call_rcu(&dentry->d_u.d_rcu, d_callback);
 }
 
 /*
@@ -1376,6 +1384,7 @@
 		return;
 	}
 
+	dentry->d_flags |= DCACHE_DELETED;
 	if (!d_unhashed(dentry))
 		__d_drop(dentry);
 
@@ -1749,7 +1758,7 @@
 
 	*--end = '\0';
 	buflen--;
-	if (!IS_ROOT(dentry) && d_unhashed(dentry)) {
+	if (!IS_ROOT(dentry) && (dentry->d_flags & DCACHE_DELETED)) {
 		buflen -= 10;
 		end -= 10;
 		if (buflen < 0)
--- linux-2.6.19-rc4/net/socket.c	2006-10-31 17:53:34.000000000 +0100
+++ linux-2.6.19-rc4-ed/net/socket.c	2006-10-31 18:39:06.000000000 +0100
@@ -304,13 +304,6 @@
 	.kill_sb =	kill_anon_super,
 };
 
-static int sockfs_delete_dentry(struct dentry *dentry)
-{
-	return 1;
-}
-static struct dentry_operations sockfs_dentry_operations = {
-	.d_delete = sockfs_delete_dentry,
-};
 
 /*
  *	Obtains the first available file descriptor and sets it up for use.
@@ -360,8 +353,9 @@
 	if (unlikely(!file->f_dentry))
 		return -ENOMEM;
 
-	file->f_dentry->d_op = &sockfs_dentry_operations;
-	d_add(file->f_dentry, SOCK_INODE(sock));
+	/* Dont insert socket dentry into global dentry hashtable */
+	d_instantiate(file->f_dentry, SOCK_INODE(sock));
+
 	file->f_vfsmnt = mntget(sock_mnt);
 	file->f_mapping = file->f_dentry->d_inode->i_mapping;
 
--- linux-2.6.19-rc4/fs/pipe.c	2006-10-31 18:53:21.000000000 +0100
+++ linux-2.6.19-rc4-ed/fs/pipe.c	2006-10-31 18:55:20.000000000 +0100
@@ -828,14 +828,6 @@
 }
 
 static struct vfsmount *pipe_mnt __read_mostly;
-static int pipefs_delete_dentry(struct dentry *dentry)
-{
-	return 1;
-}
-
-static struct dentry_operations pipefs_dentry_operations = {
-	.d_delete	= pipefs_delete_dentry,
-};
 
 static struct inode * get_pipe_inode(void)
 {
@@ -891,17 +883,15 @@
 	if (!inode)
 		goto err_file;
 
-	sprintf(name, "[%lu]", inode->i_ino);
+	this.len = sprintf(name, "[%lu]", inode->i_ino);
 	this.name = name;
-	this.len = strlen(name);
 	this.hash = inode->i_ino; /* will go */
 	err = -ENOMEM;
 	dentry = d_alloc(pipe_mnt->mnt_sb->s_root, &this);
 	if (!dentry)
 		goto err_inode;
-
-	dentry->d_op = &pipefs_dentry_operations;
-	d_add(dentry, inode);
+	/* Dont insert pipe dentry into global dentry hashtable */
+	d_instantiate(dentry, inode);
 	f->f_vfsmnt = mntget(pipe_mnt);
 	f->f_dentry = dentry;
 	f->f_mapping = inode->i_mapping;

Re: [RFC, PATCH] dont insert sockets/pipes dentries into dentry_hashtable.

[David Miller]

From: Eric Dumazet <dada1@cosmosbay.com>
Date: Tue, 31 Oct 2006 19:48:48 +0100

> We currently insert sockets/pipes dentries into the global dentry
> hashtable.  This is *useless* because there is currently no way
> these entries can be used for a lookup(). (/proc/xxx/fd/xxx uses a
> different mechanism)

It turns out that while procfs uses a different "mechanism", those
procfs symlinks do point to the real socket dentry, so when you
readlink() on it you do d_path() on the real socket dentry.

If you unhash these things, I'm pretty sure you'll see an ugly
"(deleted)" at the end of the symlink string for /proc/$pid/fd/$X
files that are sockets or something like that.

Al Viro just suggested a way around this to me:

1) Just mark the dentry HASHED by hand in the dentry flags, but don't
   actually hash it.

2) Create a special dentry->d_deleted method for sockets that returns
   0 and clears by hand the HASHED flag bit in the dentry (see what
   dput() does when this happens).

It's an abuse but it will work.

Re: [RFC, PATCH] dont insert sockets/pipes dentries into dentry_hashtable.

[Eric Dumazet]

David Miller a écrit :
> From: Eric Dumazet <dada1@cosmosbay.com>
> Date: Tue, 31 Oct 2006 19:48:48 +0100
> 
>> We currently insert sockets/pipes dentries into the global dentry
>> hashtable.  This is *useless* because there is currently no way
>> these entries can be used for a lookup(). (/proc/xxx/fd/xxx uses a
>> different mechanism)
> 
> It turns out that while procfs uses a different "mechanism", those
> procfs symlinks do point to the real socket dentry, so when you
> readlink() on it you do d_path() on the real socket dentry.
> 
> If you unhash these things, I'm pretty sure you'll see an ugly
> "(deleted)" at the end of the symlink string for /proc/$pid/fd/$X
> files that are sockets or something like that.

No no, my patch takes care of that.

You still see the right link for pipes and sockets on /proc/$pid/fd/XXX

And " (deleted)" is correctly added to deleted files.


> 
> Al Viro just suggested a way around this to me:
> 
> 1) Just mark the dentry HASHED by hand in the dentry flags, but don't
>    actually hash it.
> 
> 2) Create a special dentry->d_deleted method for sockets that returns
>    0 and clears by hand the HASHED flag bit in the dentry (see what
>    dput() does when this happens).
> 
> It's an abuse but it will work.
> 
Why hack when a proper thing can be done ?

Re: [RFC, PATCH] dont insert sockets/pipes dentries into dentry_hashtable.

[David Miller]

From: Eric Dumazet <dada1@cosmosbay.com>
Date: Wed, 01 Nov 2006 09:21:06 +0100

> No no, my patch takes care of that.
> 
> You still see the right link for pipes and sockets on /proc/$pid/fd/XXX
> 
> And " (deleted)" is correctly added to deleted files.

I see.  Excellent :-)

Re: [RFC, PATCH] dont insert sockets/pipes dentries into dentry_hashtable.

[Al Viro]

On Wed, Nov 01, 2006 at 09:21:06AM +0100, Eric Dumazet wrote:

> And " (deleted)" is correctly added to deleted files.

The hell it will.

touch a
touch b
exec 5<a
mv b a
ls -l /proc/$$/fd/5

With your patch and without it, please.

PS: getting rid of socket dentries is a bad idea with the capital "Fuck, No".
For those who want to see where does that path lead and are attracted to
trainwrecks in general I can recommend *BSD socket handling.  They have
paid quite painfully for lack of proper vnodes.  It's simply not worth
the resulting trouble.

Re: [RFC, PATCH] dont insert sockets/pipes dentries into dentry_hashtable.

[Al Viro]

On Wed, Nov 01, 2006 at 08:38:11AM +0000, Al Viro wrote:
> On Wed, Nov 01, 2006 at 09:21:06AM +0100, Eric Dumazet wrote:
> 
> > And " (deleted)" is correctly added to deleted files.
> 
> The hell it will.
> 
> touch a
> touch b
> exec 5<a
> mv b a
> ls -l /proc/$$/fd/5
> 
> With your patch and without it, please.

While we are at it,

touch a
rm a
touch a
ls -l /proc/self/fd/0 <a

With and without your patch.  Note that you never remove DCACHE_DELETED
after you've set it.

Re: [RFC, PATCH] dont insert sockets/pipes dentries into dentry_hashtable.

[Eric Dumazet]

Al Viro a écrit :
> On Wed, Nov 01, 2006 at 09:21:06AM +0100, Eric Dumazet wrote:
> 
>> And " (deleted)" is correctly added to deleted files.
> 
> The hell it will.
> 
> touch a
> touch b
> exec 5<a
> mv b a
> ls -l /proc/$$/fd/5
> 
> With your patch and without it, please.

Yes I will do, thanks.

> 
> PS: getting rid of socket dentries is a bad idea with the capital "Fuck, No".
> For those who want to see where does that path lead and are attracted to
> trainwrecks in general I can recommend *BSD socket handling.  They have
> paid quite painfully for lack of proper vnodes.  It's simply not worth
> the resulting trouble.

I have one server with one million sockets, wasting 210 MB of ram for dentries 
that are only used when some guy does some /proc/$pid/fd work

Socket hot path already dont use anymore dentries, thanks to file->private_data

Eric

Re: [RFC, PATCH] dont insert sockets/pipes dentries into dentry_hashtable.

[Eric Dumazet]

[-- Attachment #1: Type: text/plain, Size: 2052 bytes --]

David Miller a écrit :
> It turns out that while procfs uses a different "mechanism", those
> procfs symlinks do point to the real socket dentry, so when you
> readlink() on it you do d_path() on the real socket dentry.
> 
> Al Viro just suggested a way around this to me:
> 
> 1) Just mark the dentry HASHED by hand in the dentry flags, but don't
>    actually hash it.
> 
> 2) Create a special dentry->d_deleted method for sockets that returns
>    0 and clears by hand the HASHED flag bit in the dentry (see what
>    dput() does when this happens).
> 
> It's an abuse but it will work.
> 


Thank you David and Al for the feedback.

Here is a new version of the patch with your suggestions included.

If necessary, I could split this patch in 3 elementary patches. I chose to
sent it as one patch for ease of discussion.

[RFC, PATCH] dont insert sockets/pipes dentries into dentry_hashtable.

We currently insert sockets/pipes dentries into the global dentry hashtable.
This is *useless* because there is currently no way these entries can be used
for a lookup(). (/proc/xxx/fd/xxx uses a different mechanism)

Machines with a lot of sockets/pipes might suffer from longer chains in dentry
hashtable.

Since dentries an unhashed dentry means __dpath() adds a " (deleted)", the 
trick for socket/pipe dentries is to :

- Right after d_alloc(), pretend they are hashed by clearing the 
DCACHE_UNHASHED bit. __dpath() & friends work as intended.

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

- Once dput() must clear the dentry, setting again DCACHE_UNHASHED bit inside 
the custom d_delete() function provided by socket/pipe code.


[patch 1/3] Small optimization to bypass RCU freeing in d_free() for dentries 
that were never hashed (like sockets and pipes). Such dentries dont have to 
wait a RCU grace period.

[patch 2/3] Change socket code to use d_instantiate() instead of d_add()

[patch 3/3] Change pipe code to use d_instantiate() instead of d_add()

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>

[-- Attachment #2: donthash.patch --]
[-- Type: text/plain, Size: 3861 bytes --]

--- linux-2.6.19-rc4/fs/dcache.c	2006-11-01 12:38:23.000000000 +0100
+++ linux-2.6.19-rc4-ed/fs/dcache.c	2006-11-01 13:22:44.000000000 +0100
@@ -68,15 +68,19 @@
 	.age_limit = 45,
 };
 
-static void d_callback(struct rcu_head *head)
+static void __d_free(struct dentry *dentry)
 {
-	struct dentry * dentry = container_of(head, struct dentry, d_u.d_rcu);
-
 	if (dname_external(dentry))
 		kfree(dentry->d_name.name);
 	kmem_cache_free(dentry_cache, dentry); 
 }
 
+static void d_callback(struct rcu_head *head)
+{
+	struct dentry * dentry = container_of(head, struct dentry, d_u.d_rcu);
+	__d_free(dentry);
+}
+
 /*
  * no dcache_lock, please.  The caller must decrement dentry_stat.nr_dentry
  * inside dcache_lock.
@@ -85,7 +89,11 @@
 {
 	if (dentry->d_op && dentry->d_op->d_release)
 		dentry->d_op->d_release(dentry);
- 	call_rcu(&dentry->d_u.d_rcu, d_callback);
+	/* if dentry was never inserted into hash, immediate free is OK */
+	if (dentry->d_hash.pprev == NULL)
+		__d_free(dentry);
+	else
+		call_rcu(&dentry->d_u.d_rcu, d_callback);
 }
 
 /*
--- linux-2.6.19-rc4/net/socket.c	2006-11-01 12:40:27.000000000 +0100
+++ linux-2.6.19-rc4-ed/net/socket.c	2006-11-01 14:33:18.000000000 +0100
@@ -306,7 +306,14 @@
 
 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,
@@ -354,14 +361,20 @@
 
 	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 hack 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;
 
--- linux-2.6.19-rc4/fs/pipe.c	2006-11-01 12:56:05.000000000 +0100
+++ linux-2.6.19-rc4-ed/fs/pipe.c	2006-11-01 14:33:18.000000000 +0100
@@ -830,7 +830,14 @@
 static struct vfsmount *pipe_mnt __read_mostly;
 static int pipefs_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 pipefs_dentry_operations = {
@@ -891,17 +898,22 @@
 	if (!inode)
 		goto err_file;
 
-	sprintf(name, "[%lu]", inode->i_ino);
+	this.len = sprintf(name, "[%lu]", inode->i_ino);
 	this.name = name;
-	this.len = strlen(name);
-	this.hash = inode->i_ino; /* will go */
+	this.hash = 0;
 	err = -ENOMEM;
 	dentry = d_alloc(pipe_mnt->mnt_sb->s_root, &this);
 	if (!dentry)
 		goto err_inode;
 
 	dentry->d_op = &pipefs_dentry_operations;
-	d_add(dentry, inode);
+	/*
+	 * We dont want to push this dentry into global dentry hash table. 
+	 * We pretend dentry is already hashed, by unsetting DCACHE_UNHASHED
+	 * This hack permits a working /proc/$pid/fd/XXX on pipes
+	 */
+	dentry->d_flags &= ~DCACHE_UNHASHED;
+	d_instantiate(dentry, inode);
 	f->f_vfsmnt = mntget(pipe_mnt);
 	f->f_dentry = dentry;
 	f->f_mapping = inode->i_mapping;

[PATCH] [NET] dont insert socket dentries into dentry_hashtable.

[Eric Dumazet]

[-- Attachment #1: Type: text/plain, Size: 847 bytes --]

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 slow 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>

[-- Attachment #2: socket_nohash_dentry.patch --]
[-- Type: text/plain, Size: 1466 bytes --]

--- linux-2.6.19-rc6/net/socket.c	2006-11-22 17:33:41.000000000 +0100
+++ linux-2.6.19-rc6-ed/net/socket.c	2006-11-22 18:28:12.000000000 +0100
@@ -306,7 +306,14 @@ 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,
@@ -354,14 +361,20 @@ 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;
 

Re: [PATCH] [NET] dont insert socket dentries into dentry_hashtable.

[David Miller]

Andrew, I'm fine with these three patches, specifically:

[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.

Could you toss them into -mm if you haven't already?  This
makes better sense then me putting it into net-2.6.20 since
it touches FS stuff.

Thanks!

Re: [PATCH] [NET] dont insert socket dentries into dentry_hashtable.

[Andrew Morton]

On Tue, 28 Nov 2006 15:35:31 -0800 (PST)
David Miller <davem@davemloft.net> wrote:

> 
> Andrew, I'm fine with these three patches, specifically:
> 
> [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.
> 
> Could you toss them into -mm if you haven't already?

They were in rc6-mm2.

>  This
> makes better sense then me putting it into net-2.6.20 since
> it touches FS stuff.
> 

No probs, they're all lined up and ready to go, thanks.