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fuse: fix hang of single threaded fuseblk filesystem 

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@suse.de>
Cc: stable@kernel.org
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
This commit is contained in:
Miklos Szeredi 2011-02-25 14:44:58 +01:00
parent 4662db4461
commit 5a18ec176c
2 changed files with 51 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

54
fs/fuse/file.c
View File

@ -86,18 +86,52 @@ struct fuse_file *fuse_file_get(struct fuse_file *ff)
return ff;
}
static void fuse_release_end(struct fuse_conn *fc, struct fuse_req *req)
static void fuse_release_async(struct work_struct *work)
{
path_put(&req->misc.release.path);
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_file_put(struct fuse_file *ff)
static void fuse_release_end(struct fuse_conn *fc, struct fuse_req *req)
{
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, 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 @@ void fuse_release_common(struct file *file, int opcode)
* 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 @@ static void fuse_readpages_end(struct fuse_conn *fc, struct fuse_req *req)
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 ssize_t fuse_direct_write(struct file *file, const char __user *buf,
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)

6
fs/fuse/fuse_i.h
View File

@ -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
@ -262,7 +263,10 @@ struct fuse_req {
/** Data for asynchronous requests */
union {
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;