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Commit d668dc56 authored by Al Viro's avatar Al Viro
Browse files

autofs4: deal with autofs4_write/autofs4_write races 



Just serialize the actual writing of packets into pipe on
a new mutex, independent from everything else in the locking
hierarchy.  As soon as something has started feeding a piece
of packet into the pipe to daemon, we *want* everything else
about to try the same to wait until we are done.

Acked-by: default avatarIan Kent <raven@themaw.net>
Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
parent 87533332

fs/autofs4/autofs_i.h

+1 −0
Original line number Diff line number Diff line
@@ -116,6 +116,7 @@ struct autofs_sb_info { 
	int needs_reghost;

	struct super_block *sb;

	struct mutex wq_mutex;

	struct mutex pipe_mutex;

	spinlock_t fs_lock;

	struct autofs_wait_queue *queues; /* Wait queue pointer */

	spinlock_t lookup_lock;

fs/autofs4/inode.c

+1 −0
Original line number Diff line number Diff line
@@ -225,6 +225,7 @@ int autofs4_fill_super(struct super_block *s, void *data, int silent) 
	sbi->min_proto = 0;

	sbi->max_proto = 0;

	mutex_init(&sbi->wq_mutex);

	mutex_init(&sbi->pipe_mutex);

	spin_lock_init(&sbi->fs_lock);

	sbi->queues = NULL;

	spin_lock_init(&sbi->lookup_lock);

fs/autofs4/waitq.c

+5 −4
Original line number Diff line number Diff line
@@ -56,26 +56,27 @@ void autofs4_catatonic_mode(struct autofs_sb_info *sbi) 
	mutex_unlock(&sbi->wq_mutex);

}



static int autofs4_write(struct file *file, const void *addr, int bytes)

static int autofs4_write(struct autofs_sb_info *sbi,

			 struct file *file, const void *addr, int bytes)

{

	unsigned long sigpipe, flags;

	mm_segment_t fs;

	const char *data = (const char *)addr;

	ssize_t wr = 0;



	/** WARNING: this is not safe for writing more than PIPE_BUF bytes! **/



	sigpipe = sigismember(&current->pending.signal, SIGPIPE);



	/* Save pointer to user space and point back to kernel space */

	fs = get_fs();

	set_fs(KERNEL_DS);



	mutex_lock(&sbi->pipe_mutex);

	while (bytes &&

	       (wr = file->f_op->write(file,data,bytes,&file->f_pos)) > 0) {

		data += wr;

		bytes -= wr;

	}

	mutex_lock(&sbi->pipe_mutex);



	set_fs(fs);
@@ -179,7 +180,7 @@ static void autofs4_notify_daemon(struct autofs_sb_info *sbi, 


	mutex_unlock(&sbi->wq_mutex);



	if (autofs4_write(pipe, &pkt, pktsz))

	if (autofs4_write(sbi, pipe, &pkt, pktsz))

		autofs4_catatonic_mode(sbi);

	fput(pipe);

}