From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753937AbdBGLgH (ORCPT ); Tue, 7 Feb 2017 06:36:07 -0500 Received: from mail-wm0-f65.google.com ([74.125.82.65]:32908 "EHLO mail-wm0-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753667AbdBGLgE (ORCPT ); Tue, 7 Feb 2017 06:36:04 -0500 Date: Tue, 7 Feb 2017 12:35:54 +0100 From: Miklos Szeredi To: Al Viro Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Linux NFS list , ceph-devel@vger.kernel.org, lustre-devel@lists.lustre.org, v9fs-developer@lists.sourceforge.net, Linus Torvalds , Jan Kara , Chris Wilson , "Kirill A. Shutemov" , Jeff Layton Subject: Re: [PATCH v3 0/2] iov_iter: allow iov_iter_get_pages_alloc to allocate more pages per call Message-ID: <20170207113554.GA30656@veci.piliscsaba.szeredi.hu> References: <20170205015145.GB13195@ZenIV.linux.org.uk> <20170205210151.GD13195@ZenIV.linux.org.uk> <20170205220445.GE13195@ZenIV.linux.org.uk> <20170206030532.GF13195@ZenIV.linux.org.uk> <20170206095706.GG13195@ZenIV.linux.org.uk> <20170207071909.GI13195@ZenIV.linux.org.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170207071909.GI13195@ZenIV.linux.org.uk> User-Agent: Mutt/1.7.1 (2016-10-04) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Feb 07, 2017 at 07:19:09AM +0000, Al Viro wrote: > Speaking of refcounting - what's going on with fuse_file one? My reading > of that code is that you have 4 states of that thing: > * new (just created, fallback request allocated, use fuse_file_free() > to kill). Refcount is 0. > * intermediate - in fact it's already opened, but still not > put into ->private_data. Refcount is still 0. Use fuse_sync_release() to kill. > * live - normal refcounting (fuse_file_get()/fuse_file_put()). > * shutdown - refcount has reached 0. Can't happen until ->release() > (obviously - ->private_data holds a counting reference), some pieces of > fuse_sync_release() correspond to some stuff in fuse_release_common(), some - > to final fuse_file_put(). > > To make it even more convoluted, cuse is using fuse_sync_release() and > apparently relies upon no references being grabbed after fuse_do_open(), > so that thing can be called with refcount 0 *or* refcount 1. Indeed, ugly. Following should clean that up somewhat. The states remain what they are but refcounting is at least consistent now. This also fixes a missing FR_FORCE in the sync case. > Another thing: what guarantees that places in writepages-related paths > where we store a reference into req->ff won't hit a request with already > non-NULL ->ff? Well, it is set before being sent (queued onto queued_writes or queued on the fuse device), but not when queued as secondary request onto an already in-flight one. It looks okay to me. Thanks, Miklos diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c index 811fd8929a18..e816166ce42f 100644 --- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -473,7 +473,7 @@ static int fuse_create_open(struct inode *dir, struct dentry *entry, if (err) { fuse_sync_release(ff, flags); } else { - file->private_data = fuse_file_get(ff); + file->private_data = ff; fuse_finish_open(inode, file); } return err; diff --git a/fs/fuse/file.c b/fs/fuse/file.c index 2401c5dabb2a..94cc4ab01f9a 100644 --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -58,7 +58,7 @@ struct fuse_file *fuse_file_alloc(struct fuse_conn *fc) } INIT_LIST_HEAD(&ff->write_entry); - atomic_set(&ff->count, 0); + atomic_set(&ff->count, 1); RB_CLEAR_NODE(&ff->polled_node); init_waitqueue_head(&ff->poll_wait); @@ -75,7 +75,7 @@ void fuse_file_free(struct fuse_file *ff) kfree(ff); } -struct fuse_file *fuse_file_get(struct fuse_file *ff) +static struct fuse_file *fuse_file_get(struct fuse_file *ff) { atomic_inc(&ff->count); return ff; @@ -100,6 +100,7 @@ static void fuse_file_put(struct fuse_file *ff, bool sync) iput(req->misc.release.inode); fuse_put_request(ff->fc, req); } else if (sync) { + __set_bit(FR_FORCE, &req->flags); __clear_bit(FR_BACKGROUND, &req->flags); fuse_request_send(ff->fc, req); iput(req->misc.release.inode); @@ -146,7 +147,7 @@ int fuse_do_open(struct fuse_conn *fc, u64 nodeid, struct file *file, ff->open_flags &= ~FOPEN_DIRECT_IO; ff->nodeid = nodeid; - file->private_data = fuse_file_get(ff); + file->private_data = ff; return 0; } @@ -297,13 +298,9 @@ static int fuse_release(struct inode *inode, struct file *file) void fuse_sync_release(struct fuse_file *ff, int flags) { - WARN_ON(atomic_read(&ff->count) > 1); + WARN_ON(atomic_read(&ff->count) != 1); fuse_prepare_release(ff, flags, FUSE_RELEASE); - __set_bit(FR_FORCE, &ff->reserved_req->flags); - __clear_bit(FR_BACKGROUND, &ff->reserved_req->flags); - fuse_request_send(ff->fc, ff->reserved_req); - fuse_put_request(ff->fc, ff->reserved_req); - kfree(ff); + fuse_file_put(ff, true); } EXPORT_SYMBOL_GPL(fuse_sync_release); diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h index 91307940c8ac..83f797271aef 100644 --- a/fs/fuse/fuse_i.h +++ b/fs/fuse/fuse_i.h @@ -732,7 +732,6 @@ void fuse_read_fill(struct fuse_req *req, struct file *file, int fuse_open_common(struct inode *inode, struct file *file, bool isdir); struct fuse_file *fuse_file_alloc(struct fuse_conn *fc); -struct fuse_file *fuse_file_get(struct fuse_file *ff); void fuse_file_free(struct fuse_file *ff); void fuse_finish_open(struct inode *inode, struct file *file); From mboxrd@z Thu Jan 1 00:00:00 1970 From: Miklos Szeredi Subject: Re: [PATCH v3 0/2] iov_iter: allow iov_iter_get_pages_alloc to allocate more pages per call Date: Tue, 7 Feb 2017 12:35:54 +0100 Message-ID: <20170207113554.GA30656@veci.piliscsaba.szeredi.hu> References: <20170205015145.GB13195@ZenIV.linux.org.uk> <20170205210151.GD13195@ZenIV.linux.org.uk> <20170205220445.GE13195@ZenIV.linux.org.uk> <20170206030532.GF13195@ZenIV.linux.org.uk> <20170206095706.GG13195@ZenIV.linux.org.uk> <20170207071909.GI13195@ZenIV.linux.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <20170207071909.GI13195-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org> Sender: linux-nfs-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Al Viro Cc: linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Linux NFS list , ceph-devel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, lustre-devel-aLEFhgZF4x6X6Mz3xDxJMA@public.gmane.org, v9fs-developer-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org, Linus Torvalds , Jan Kara , Chris Wilson , "Kirill A. Shutemov" , Jeff Layton List-Id: ceph-devel.vger.kernel.org On Tue, Feb 07, 2017 at 07:19:09AM +0000, Al Viro wrote: > Speaking of refcounting - what's going on with fuse_file one? My reading > of that code is that you have 4 states of that thing: > * new (just created, fallback request allocated, use fuse_file_free() > to kill). Refcount is 0. > * intermediate - in fact it's already opened, but still not > put into ->private_data. Refcount is still 0. Use fuse_sync_release() to kill. > * live - normal refcounting (fuse_file_get()/fuse_file_put()). > * shutdown - refcount has reached 0. Can't happen until ->release() > (obviously - ->private_data holds a counting reference), some pieces of > fuse_sync_release() correspond to some stuff in fuse_release_common(), some - > to final fuse_file_put(). > > To make it even more convoluted, cuse is using fuse_sync_release() and > apparently relies upon no references being grabbed after fuse_do_open(), > so that thing can be called with refcount 0 *or* refcount 1. Indeed, ugly. Following should clean that up somewhat. The states remain what they are but refcounting is at least consistent now. This also fixes a missing FR_FORCE in the sync case. > Another thing: what guarantees that places in writepages-related paths > where we store a reference into req->ff won't hit a request with already > non-NULL ->ff? Well, it is set before being sent (queued onto queued_writes or queued on the fuse device), but not when queued as secondary request onto an already in-flight one. It looks okay to me. Thanks, Miklos diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c index 811fd8929a18..e816166ce42f 100644 --- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -473,7 +473,7 @@ static int fuse_create_open(struct inode *dir, struct dentry *entry, if (err) { fuse_sync_release(ff, flags); } else { - file->private_data = fuse_file_get(ff); + file->private_data = ff; fuse_finish_open(inode, file); } return err; diff --git a/fs/fuse/file.c b/fs/fuse/file.c index 2401c5dabb2a..94cc4ab01f9a 100644 --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -58,7 +58,7 @@ struct fuse_file *fuse_file_alloc(struct fuse_conn *fc) } INIT_LIST_HEAD(&ff->write_entry); - atomic_set(&ff->count, 0); + atomic_set(&ff->count, 1); RB_CLEAR_NODE(&ff->polled_node); init_waitqueue_head(&ff->poll_wait); @@ -75,7 +75,7 @@ void fuse_file_free(struct fuse_file *ff) kfree(ff); } -struct fuse_file *fuse_file_get(struct fuse_file *ff) +static struct fuse_file *fuse_file_get(struct fuse_file *ff) { atomic_inc(&ff->count); return ff; @@ -100,6 +100,7 @@ static void fuse_file_put(struct fuse_file *ff, bool sync) iput(req->misc.release.inode); fuse_put_request(ff->fc, req); } else if (sync) { + __set_bit(FR_FORCE, &req->flags); __clear_bit(FR_BACKGROUND, &req->flags); fuse_request_send(ff->fc, req); iput(req->misc.release.inode); @@ -146,7 +147,7 @@ int fuse_do_open(struct fuse_conn *fc, u64 nodeid, struct file *file, ff->open_flags &= ~FOPEN_DIRECT_IO; ff->nodeid = nodeid; - file->private_data = fuse_file_get(ff); + file->private_data = ff; return 0; } @@ -297,13 +298,9 @@ static int fuse_release(struct inode *inode, struct file *file) void fuse_sync_release(struct fuse_file *ff, int flags) { - WARN_ON(atomic_read(&ff->count) > 1); + WARN_ON(atomic_read(&ff->count) != 1); fuse_prepare_release(ff, flags, FUSE_RELEASE); - __set_bit(FR_FORCE, &ff->reserved_req->flags); - __clear_bit(FR_BACKGROUND, &ff->reserved_req->flags); - fuse_request_send(ff->fc, ff->reserved_req); - fuse_put_request(ff->fc, ff->reserved_req); - kfree(ff); + fuse_file_put(ff, true); } EXPORT_SYMBOL_GPL(fuse_sync_release); diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h index 91307940c8ac..83f797271aef 100644 --- a/fs/fuse/fuse_i.h +++ b/fs/fuse/fuse_i.h @@ -732,7 +732,6 @@ void fuse_read_fill(struct fuse_req *req, struct file *file, int fuse_open_common(struct inode *inode, struct file *file, bool isdir); struct fuse_file *fuse_file_alloc(struct fuse_conn *fc); -struct fuse_file *fuse_file_get(struct fuse_file *ff); void fuse_file_free(struct fuse_file *ff); void fuse_finish_open(struct inode *inode, struct file *file); -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html