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Message-Id: <20110330210645.58B543E1A05@tassilo.jf.intel.com>
Date: Wed, 30 Mar 2011 14:06:45 -0700 (PDT)
From: Andi Kleen <andi@...stfloor.org>
To: mszeredi@...e.cz, gregkh@...e.de, ak@...ux.intel.com,
linux-kernel@...r.kernel.org, stable@...nel.org,
tim.bird@...sony.com
Subject: [PATCH] [163/275] fuse: fix hang of single threaded fuseblk filesystem
2.6.35-longterm review patch. If anyone has any objections, please let me know.
------------------
From: Miklos Szeredi <mszeredi@...e.cz>
commit 5a18ec176c934ca1bc9dc61580a5e0e90a9b5733 upstream.
Single threaded NTFS-3G could get stuck if a delayed RELEASE reply
triggered a DESTROY request via path_put().
Fix this by
a) making RELEASE requests synchronous, whenever possible, on fuseblk
filesystems
b) if not possible (triggered by an asynchronous read/write) then do
the path_put() in a separate thread with schedule_work().
Reported-by: Oliver Neukum <oneukum@...e.de>
Signed-off-by: Miklos Szeredi <mszeredi@...e.cz>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>
Signed-off-by: Andi Kleen <ak@...ux.intel.com>
---
fs/fuse/file.c | 52 +++++++++++++++++++++++++++++++++++++++++++++-------
fs/fuse/fuse_i.h | 6 +++++-
2 files changed, 50 insertions(+), 8 deletions(-)
Index: linux-2.6.35.y/fs/fuse/file.c
===================================================================
--- linux-2.6.35.y.orig/fs/fuse/file.c 2011-03-29 22:50:59.901725684 -0700
+++ linux-2.6.35.y/fs/fuse/file.c 2011-03-29 23:03:01.641258175 -0700
@@ -86,18 +86,52 @@
return ff;
}
+static void fuse_release_async(struct work_struct *work)
+{
+ struct fuse_req *req;
+ struct fuse_conn *fc;
+ struct path path;
+
+ req = container_of(work, struct fuse_req, misc.release.work);
+ path = req->misc.release.path;
+ fc = get_fuse_conn(path.dentry->d_inode);
+
+ fuse_put_request(fc, req);
+ path_put(&path);
+}
+
static void fuse_release_end(struct fuse_conn *fc, struct fuse_req *req)
{
- path_put(&req->misc.release.path);
+ if (fc->destroy_req) {
+ /*
+ * If this is a fuseblk mount, then it's possible that
+ * releasing the path will result in releasing the
+ * super block and sending the DESTROY request. If
+ * the server is single threaded, this would hang.
+ * For this reason do the path_put() in a separate
+ * thread.
+ */
+ atomic_inc(&req->count);
+ INIT_WORK(&req->misc.release.work, fuse_release_async);
+ schedule_work(&req->misc.release.work);
+ } else {
+ path_put(&req->misc.release.path);
+ }
}
-static void fuse_file_put(struct fuse_file *ff)
+static void fuse_file_put(struct fuse_file *ff, bool sync)
{
if (atomic_dec_and_test(&ff->count)) {
struct fuse_req *req = ff->reserved_req;
- req->end = fuse_release_end;
- fuse_request_send_background(ff->fc, req);
+ if (sync) {
+ fuse_request_send(ff->fc, req);
+ path_put(&req->misc.release.path);
+ fuse_put_request(ff->fc, req);
+ } else {
+ req->end = fuse_release_end;
+ fuse_request_send_background(ff->fc, req);
+ }
kfree(ff);
}
}
@@ -219,8 +253,12 @@
* Normally this will send the RELEASE request, however if
* some asynchronous READ or WRITE requests are outstanding,
* the sending will be delayed.
+ *
+ * Make the release synchronous if this is a fuseblk mount,
+ * synchronous RELEASE is allowed (and desirable) in this case
+ * because the server can be trusted not to screw up.
*/
- fuse_file_put(ff);
+ fuse_file_put(ff, ff->fc->destroy_req != NULL);
}
static int fuse_open(struct inode *inode, struct file *file)
@@ -558,7 +596,7 @@
page_cache_release(page);
}
if (req->ff)
- fuse_file_put(req->ff);
+ fuse_file_put(req->ff, false);
}
static void fuse_send_readpages(struct fuse_req *req, struct file *file)
@@ -1137,7 +1175,7 @@
static void fuse_writepage_free(struct fuse_conn *fc, struct fuse_req *req)
{
__free_page(req->pages[0]);
- fuse_file_put(req->ff);
+ fuse_file_put(req->ff, false);
}
static void fuse_writepage_finish(struct fuse_conn *fc, struct fuse_req *req)
Index: linux-2.6.35.y/fs/fuse/fuse_i.h
===================================================================
--- linux-2.6.35.y.orig/fs/fuse/fuse_i.h 2011-03-29 22:50:59.901725684 -0700
+++ linux-2.6.35.y/fs/fuse/fuse_i.h 2011-03-29 23:03:01.642258149 -0700
@@ -21,6 +21,7 @@
#include <linux/rwsem.h>
#include <linux/rbtree.h>
#include <linux/poll.h>
+#include <linux/workqueue.h>
/** Max number of pages that can be used in a single read request */
#define FUSE_MAX_PAGES_PER_REQ 32
@@ -257,7 +258,10 @@
union {
struct fuse_forget_in forget_in;
struct {
- struct fuse_release_in in;
+ union {
+ struct fuse_release_in in;
+ struct work_struct work;
+ };
struct path path;
} release;
struct fuse_init_in init_in;
--
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