Re: [PATCH 2/2] Replace pid_t in autofs with struct pid reference

From: Ian Kent
Date: Fri Mar 16 2007 - 12:49:33 EST

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In reply to: Cedric Le Goater: "Re: [PATCH 2/2] Replace pid_t in autofs with struct pid reference"
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On Fri, 2007-03-16 at 15:44 +0100, Cedric Le Goater wrote:
> > How about you send over the autofs4 bit and I'll have a look (the autofs
> > patch looked fine). That would save me a bit of time and if there are
> > any changes needed I can send an updated patch for you guys to review. I
> > don't think autofs4 uses pids differently, in principle, than autofs so
> > it "should" be straight forward.
>
> Here's the latest.

That looks OK to me, assuming the "find_get_pid" and friends do what
they suggest, but I'll give it a closer look tomorrow.

A ref count is used here, what affect does that have on a thread (or
process) that may go away (or be summarily killed) without umounting the
mount?

Thanks
Ian

>
> thanks,
>
> C.
>
> From: Sukadev Bhattiprolu <sukadev@xxxxxxxxxx>
>
> Subject: Replace pid_t in autofs4 with struct pid reference.
>
> Make autofs4 container-friendly by caching struct pid reference rather
> than pid_t and using pid_nr() to retreive a task's pid_t.
>
> ChangeLog:
> - Fix Eric Biederman's comments - Use find_get_pid() to hold a
> reference to oz_pgrp and release while unmounting; separate out
> changes to autofs and autofs4.
> - Also rollback my earlier change to autofs_wait_queue (pid and tgid
> in the wait queue are just used to write to a userspace daemon's
> pipe).
> - Fix Cedric's comments: retain old prototype of parse_options()
> and move necessary change to its caller.
>
> Signed-off-by: Sukadev Bhattiprolu <sukadev@xxxxxxxxxx>
> Cc: Cedric Le Goater <clg@xxxxxxxxxx>
> Cc: Dave Hansen <haveblue@xxxxxxxxxx>
> Cc: Serge Hallyn <serue@xxxxxxxxxx>
> Cc: Eric Biederman <ebiederm@xxxxxxxxxxxx>
> Cc: containers@xxxxxxxxxxxxxx
>
> ---
> fs/autofs4/autofs_i.h | 6 +++---
> fs/autofs4/inode.c | 21 ++++++++++++++++-----
> fs/autofs4/root.c | 3 ++-
> fs/autofs4/waitq.c | 4 ++--
> 4 files changed, 23 insertions(+), 11 deletions(-)
>
> Index: 2.6.20/fs/autofs4/autofs_i.h
> ===================================================================
> --- 2.6.20.orig/fs/autofs4/autofs_i.h
> +++ 2.6.20/fs/autofs4/autofs_i.h
> @@ -35,7 +35,7 @@
> /* #define DEBUG */
>
> #ifdef DEBUG
> -#define DPRINTK(fmt,args...) do { printk(KERN_DEBUG "pid %d: %s: " fmt "\n" , current->pid , __FUNCTION__ , ##args); } while(0)
> +#define DPRINTK(fmt,args...) do { printk(KERN_DEBUG "pid %d: %s: " fmt "\n" , pid_nr(task_pid(current)), __FUNCTION__ , ##args); } while(0)
> #else
> #define DPRINTK(fmt,args...) do {} while(0)
> #endif
> @@ -96,7 +96,7 @@ struct autofs_sb_info {
> u32 magic;
> int pipefd;
> struct file *pipe;
> - pid_t oz_pgrp;
> + struct pid *oz_pgrp;
> int catatonic;
> int version;
> int sub_version;
> @@ -127,7 +127,7 @@ static inline struct autofs_info *autofs
> filesystem without "magic".) */
>
> static inline int autofs4_oz_mode(struct autofs_sb_info *sbi) {
> - return sbi->catatonic || process_group(current) == sbi->oz_pgrp;
> + return sbi->catatonic || task_pgrp(current) == sbi->oz_pgrp;
> }
>
> /* Does a dentry have some pending activity? */
> Index: 2.6.20/fs/autofs4/inode.c
> ===================================================================
> --- 2.6.20.orig/fs/autofs4/inode.c
> +++ 2.6.20/fs/autofs4/inode.c
> @@ -163,6 +163,8 @@ void autofs4_kill_sb(struct super_block
> if ( !sbi->catatonic )
> autofs4_catatonic_mode(sbi); /* Free wait queues, close pipe */
>
> + put_pid(sbi->oz_pgrp);
> +
> /* Clean up and release dangling references */
> autofs4_force_release(sbi);
>
> @@ -181,7 +183,7 @@ static int autofs4_show_options(struct s
> return 0;
>
> seq_printf(m, ",fd=%d", sbi->pipefd);
> - seq_printf(m, ",pgrp=%d", sbi->oz_pgrp);
> + seq_printf(m, ",pgrp=%d", pid_nr(sbi->oz_pgrp));
> seq_printf(m, ",timeout=%lu", sbi->exp_timeout/HZ);
> seq_printf(m, ",minproto=%d", sbi->min_proto);
> seq_printf(m, ",maxproto=%d", sbi->max_proto);
> @@ -311,6 +313,7 @@ int autofs4_fill_super(struct super_bloc
> int pipefd;
> struct autofs_sb_info *sbi;
> struct autofs_info *ino;
> + pid_t pgid;
>
> sbi = kmalloc(sizeof(*sbi), GFP_KERNEL);
> if (!sbi)
> @@ -325,7 +328,6 @@ int autofs4_fill_super(struct super_bloc
> sbi->pipe = NULL;
> sbi->catatonic = 1;
> sbi->exp_timeout = 0;
> - sbi->oz_pgrp = process_group(current);
> sbi->sb = s;
> sbi->version = 0;
> sbi->sub_version = 0;
> @@ -361,7 +363,7 @@ int autofs4_fill_super(struct super_bloc
>
> /* Can this call block? */
> if (parse_options(data, &pipefd, &root_inode->i_uid, &root_inode->i_gid,
> - &sbi->oz_pgrp, &sbi->type, &sbi->min_proto,
> + &pgid, &sbi->type, &sbi->min_proto,
> &sbi->max_proto)) {
> printk("autofs: called with bogus options\n");
> goto fail_dput;
> @@ -389,12 +391,19 @@ int autofs4_fill_super(struct super_bloc
> sbi->version = sbi->max_proto;
> sbi->sub_version = AUTOFS_PROTO_SUBVERSION;
>
> - DPRINTK("pipe fd = %d, pgrp = %u", pipefd, sbi->oz_pgrp);
> + DPRINTK("pipe fd = %d, pgrp = %u", pipefd, pgid);
> +
> + sbi->oz_pgrp = find_get_pid(pgid);
> + if (!sbi->oz_pgrp) {
> + printk("autofs: could not find process group %d\n", pgid);
> + goto fail_dput;
> + }
> +
> pipe = fget(pipefd);
>
> if (!pipe) {
> printk("autofs: could not open pipe file descriptor\n");
> - goto fail_dput;
> + goto fail_put_pid;
> }
> if (!pipe->f_op || !pipe->f_op->write)
> goto fail_fput;
> @@ -415,6 +424,8 @@ fail_fput:
> printk("autofs: pipe file descriptor does not contain proper ops\n");
> fput(pipe);
> /* fall through */
> +fail_put_pid:
> + put_pid(sbi->oz_pgrp);
> fail_dput:
> dput(root);
> goto fail_free;
> Index: 2.6.20/fs/autofs4/root.c
> ===================================================================
> --- 2.6.20.orig/fs/autofs4/root.c
> +++ 2.6.20/fs/autofs4/root.c
> @@ -495,7 +495,8 @@ static struct dentry *autofs4_lookup(str
> oz_mode = autofs4_oz_mode(sbi);
>
> DPRINTK("pid = %u, pgrp = %u, catatonic = %d, oz_mode = %d",
> - current->pid, process_group(current), sbi->catatonic, oz_mode);
> + pid_nr(task_pid(current)), process_group(current),
> + sbi->catatonic, oz_mode);
>
> /*
> * Mark the dentry incomplete, but add it. This is needed so
> Index: 2.6.20/fs/autofs4/waitq.c
> ===================================================================
> --- 2.6.20.orig/fs/autofs4/waitq.c
> +++ 2.6.20/fs/autofs4/waitq.c
> @@ -292,8 +292,8 @@ int autofs4_wait(struct autofs_sb_info *
> wq->ino = autofs4_get_ino(sbi);
> wq->uid = current->uid;
> wq->gid = current->gid;
> - wq->pid = current->pid;
> - wq->tgid = current->tgid;
> + wq->pid = pid_nr(task_pid(current));
> + wq->tgid = pid_nr(task_tgid(current));
> wq->status = -EINTR; /* Status return if interrupted */
> atomic_set(&wq->wait_ctr, 2);
> mutex_unlock(&sbi->wq_mutex);

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Next message: Jeremy Fitzhardinge: "Re: Stolen and degraded time and schedulers"
Previous message: Chris Wright: "Re: [patch 15/26] Xen-paravirt_ops: Add apply_to_page_range() which applies a function to a pte range."
In reply to: Cedric Le Goater: "Re: [PATCH 2/2] Replace pid_t in autofs with struct pid reference"
Next in thread: Eric W. Biederman: "Re: [PATCH 2/2] Replace pid_t in autofs with struct pid reference"
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