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[PATCH] 9p: fix segfault caused by race condition in meta-data operations

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Running dbench multithreaded exposed a race condition where fid structures
were removed while in use.  This patch adds semaphores to meta-data operations
to protect the fid structure.  Some cleanup of error-case handling in the
inode operations is also included.

Signed-off-by: Eric Van Hensbergen <ericvh@gmail.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Eric Van Hensbergen
2007-01-26 00:57:06 -08:00
committed by Linus Torvalds
parent ff76e1dfc8
commit da977b2c7e
4 changed files with 196 additions and 129 deletions
Download Patch File Download Diff File Expand all files Collapse all files
fs/9p/fid.c
+66 -3
View File
@@ -25,6 +25,7 @@
#include <linux/fs.h>
#include <linux/sched.h>
#include <linux/idr.h>
#include <asm/semaphore.h>
#include "debug.h"
#include "v9fs.h"
@@ -84,6 +85,7 @@ struct v9fs_fid *v9fs_fid_create(struct v9fs_session_info *v9ses, int fid)
new->iounit = 0;
new->rdir_pos = 0;
new->rdir_fcall = NULL;
init_MUTEX(&new->lock);
INIT_LIST_HEAD(&new->list);
return new;
@@ -102,11 +104,11 @@ void v9fs_fid_destroy(struct v9fs_fid *fid)
}
/**
* v9fs_fid_lookup - retrieve the right fid from a particular dentry
* v9fs_fid_lookup - return a locked fid from a dentry
* @dentry: dentry to look for fid in
* @type: intent of lookup (operation or traversal)
*
* find a fid in the dentry
* find a fid in the dentry, obtain its semaphore and return a reference to it.
* code calling lookup is responsible for releasing lock
*
* TODO: only match fids that have the same uid as current user
*
@@ -124,7 +126,68 @@ struct v9fs_fid *v9fs_fid_lookup(struct dentry *dentry)
if (!return_fid) {
dprintk(DEBUG_ERROR, "Couldn't find a fid in dentry\n");
return_fid = ERR_PTR(-EBADF);
}
if(down_interruptible(&return_fid->lock))
return ERR_PTR(-EINTR);
return return_fid;
}
/**
* v9fs_fid_clone - lookup the fid for a dentry, clone a private copy and release it
* @dentry: dentry to look for fid in
*
* find a fid in the dentry and then clone to a new private fid
*
* TODO: only match fids that have the same uid as current user
*
*/
struct v9fs_fid *v9fs_fid_clone(struct dentry *dentry)
{
struct v9fs_session_info *v9ses = v9fs_inode2v9ses(dentry->d_inode);
struct v9fs_fid *base_fid, *new_fid = ERR_PTR(-EBADF);
struct v9fs_fcall *fcall = NULL;
int fid, err;
base_fid = v9fs_fid_lookup(dentry);
if(IS_ERR(base_fid))
return base_fid;
if(base_fid) { /* clone fid */
fid = v9fs_get_idpool(&v9ses->fidpool);
if (fid < 0) {
eprintk(KERN_WARNING, "newfid fails!\n");
new_fid = ERR_PTR(-ENOSPC);
goto Release_Fid;
}
err = v9fs_t_walk(v9ses, base_fid->fid, fid, NULL, &fcall);
if (err < 0) {
dprintk(DEBUG_ERROR, "clone walk didn't work\n");
v9fs_put_idpool(fid, &v9ses->fidpool);
new_fid = ERR_PTR(err);
goto Free_Fcall;
}
new_fid = v9fs_fid_create(v9ses, fid);
if (new_fid == NULL) {
dprintk(DEBUG_ERROR, "out of memory\n");
new_fid = ERR_PTR(-ENOMEM);
}
Free_Fcall:
kfree(fcall);
}
Release_Fid:
up(&base_fid->lock);
return new_fid;
}
void v9fs_fid_clunk(struct v9fs_session_info *v9ses, struct v9fs_fid *fid)
{
v9fs_t_clunk(v9ses, fid->fid);
v9fs_fid_destroy(fid);
}