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bh=hDJHYc97KMDLlm6S3/gxEyIh/ud6RnO4VX293pyL/Ic=; b=V7ye42bEQUysOAk402c2v6tlcJPeJUfRplqIUL1iqSXcuAwMAZMO4v2N7C0hwcnqibx3fE v12mqE+gPy9cAgViPdfSO6tTQGDUb23CeRAijGhImoFmuxGhmhGL6rLM8qTFyKmKm1zhYg vuinOt5BZHnmioNKHH1aHxBwZerdC/s= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-429-FIF5Dd1mPyeypsj0-U5Z0A-1; Wed, 16 Dec 2020 04:50:07 -0500 X-MC-Unique: FIF5Dd1mPyeypsj0-U5Z0A-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 9DFDC15735; Wed, 16 Dec 2020 09:50:05 +0000 (UTC) Received: from redhat.com (ovpn-115-177.ams2.redhat.com [10.36.115.177]) by smtp.corp.redhat.com (Postfix) with ESMTPS id DE6C9709B0; Wed, 16 Dec 2020 09:50:02 +0000 (UTC) Date: Wed, 16 Dec 2020 09:49:59 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Vladimir Sementsov-Ogievskiy Subject: Re: [PATCH v5] file-posix: detect the lock using the real file Message-ID: <20201216094959.GC189795@redhat.com> References: <1608029636-31442-1-git-send-email-fengli@smartx.com> <05c96a12-b343-fec4-4060-7110bb0850d0@virtuozzo.com> MIME-Version: 1.0 In-Reply-To: <05c96a12-b343-fec4-4060-7110bb0850d0@virtuozzo.com> User-Agent: Mutt/1.14.6 (2020-07-11) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=berrange@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Received-SPF: pass client-ip=216.205.24.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: Kevin Wolf , lifeng1519@gmail.com, "open list:raw" , "open list:All patches CC here" , Max Reitz , Li Feng , kyle@smartx.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Wed, Dec 16, 2020 at 11:22:38AM +0300, Vladimir Sementsov-Ogievskiy wrote: > 15.12.2020 13:53, Li Feng wrote: > > This patch addresses this issue: > > When accessing a volume on an NFS filesystem without supporting the file lock, > > tools, like qemu-img, will complain "Failed to lock byte 100". > > > > In the original code, the qemu_has_ofd_lock will test the lock on the > > "/dev/null" pseudo-file. Actually, the file.locking is per-drive property, > > which depends on the underlay filesystem. > > > > In this patch, add a new 'qemu_has_file_lock' to detect whether the > > file supports the file lock. And disable the lock when the underlay file > > system doesn't support locks. > > > > Signed-off-by: Li Feng > > --- > > v5: simplify the code. > > v4: use the fd as the qemu_has_file_lock argument. > > v3: don't call the qemu_has_ofd_lock, use a new function instead. > > v2: remove the refactoring. > > --- > > block/file-posix.c | 61 +++++++++++++++++++++++--------------------- > > include/qemu/osdep.h | 1 + > > util/osdep.c | 14 ++++++++++ > > 3 files changed, 47 insertions(+), 29 deletions(-) > > > > diff --git a/block/file-posix.c b/block/file-posix.c > > index 806764f7e3..4e00111031 100644 > > --- a/block/file-posix.c > > +++ b/block/file-posix.c > > @@ -584,6 +584,21 @@ static int raw_open_common(BlockDriverState *bs, QDict *options, > > s->use_linux_io_uring = (aio == BLOCKDEV_AIO_OPTIONS_IO_URING); > > #endif > > + s->open_flags = open_flags; > > + raw_parse_flags(bdrv_flags, &s->open_flags, false); > > + > > + s->fd = -1; > > + fd = qemu_open(filename, s->open_flags, errp); > > + ret = fd < 0 ? -errno : 0; > > + > > + if (ret < 0) { > > + if (ret == -EROFS) { > > + ret = -EACCES; > > + } > > + goto fail; > > + } > > + s->fd = fd; > > + > > locking = qapi_enum_parse(&OnOffAuto_lookup, > > qemu_opt_get(opts, "locking"), > > ON_OFF_AUTO_AUTO, &local_err); > > @@ -606,7 +621,7 @@ static int raw_open_common(BlockDriverState *bs, QDict *options, > > s->use_lock = false; > > break; > > In case of ON_OFF_AUTO_ON: we do check qemu_has_ofd_lock() and print a warning. > > Probably we can also check new qemu_has_file_lock() and just do early fail, not waiting for permissions update.. > > > case ON_OFF_AUTO_AUTO: > > - s->use_lock = qemu_has_ofd_lock(); > > + s->use_lock = qemu_has_file_lock(s->fd) && qemu_has_ofd_lock(); > > break; > > default: > > abort(); > > @@ -625,22 +640,6 @@ static int raw_open_common(BlockDriverState *bs, QDict *options, > > s->drop_cache = qemu_opt_get_bool(opts, "drop-cache", true); > > s->check_cache_dropped = qemu_opt_get_bool(opts, "x-check-cache-dropped", > > false); > > - > > - s->open_flags = open_flags; > > - raw_parse_flags(bdrv_flags, &s->open_flags, false); > > - > > - s->fd = -1; > > - fd = qemu_open(filename, s->open_flags, errp); > > - ret = fd < 0 ? -errno : 0; > > - > > - if (ret < 0) { > > - if (ret == -EROFS) { > > - ret = -EACCES; > > - } > > - goto fail; > > - } > > - s->fd = fd; > > - > > /* Check s->open_flags rather than bdrv_flags due to auto-read-only */ > > if (s->open_flags & O_RDWR) { > > ret = check_hdev_writable(s->fd); > > @@ -2388,6 +2387,7 @@ raw_co_create(BlockdevCreateOptions *options, Error **errp) > > int fd; > > uint64_t perm, shared; > > int result = 0; > > + bool use_lock; > > /* Validate options and set default values */ > > assert(options->driver == BLOCKDEV_DRIVER_FILE); > > @@ -2428,19 +2428,22 @@ raw_co_create(BlockdevCreateOptions *options, Error **errp) > > perm = BLK_PERM_WRITE | BLK_PERM_RESIZE; > > shared = BLK_PERM_ALL & ~BLK_PERM_RESIZE; > > - /* Step one: Take locks */ > > - result = raw_apply_lock_bytes(NULL, fd, perm, ~shared, false, errp); > > - if (result < 0) { > > - goto out_close; > > - } > > + use_lock = qemu_has_file_lock(fd); > > + if (use_lock) { > > + /* Step one: Take locks */ > > + result = raw_apply_lock_bytes(NULL, fd, perm, ~shared, false, errp); > > + if (result < 0) { > > + goto out_close; > > + } > > - /* Step two: Check that nobody else has taken conflicting locks */ > > - result = raw_check_lock_bytes(fd, perm, shared, errp); > > - if (result < 0) { > > - error_append_hint(errp, > > - "Is another process using the image [%s]?\n", > > - file_opts->filename); > > - goto out_unlock; > > + /* Step two: Check that nobody else has taken conflicting locks */ > > + result = raw_check_lock_bytes(fd, perm, shared, errp); > > + if (result < 0) { > > + error_append_hint(errp, > > + "Is another process using the image [%s]?\n", > > + file_opts->filename); > > + goto out_unlock; > > + } > > } > > In raw_co_create(), I think you should also update code under "out_unlock:", we shouldn't > call raw_apply_lock_bytes(), when use_lock is false. > > > Another thing is call to raw_apply_lock_bytes() in raw_check_perm(). Looks like a preexisting bug. Why don't we check for s->use_lock? > > > /* Clear the file by truncating it to 0 */ > > diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h > > index f9ec8c84e9..c7587be99d 100644 > > --- a/include/qemu/osdep.h > > +++ b/include/qemu/osdep.h > > @@ -513,6 +513,7 @@ int qemu_lock_fd(int fd, int64_t start, int64_t len, bool exclusive); > > int qemu_unlock_fd(int fd, int64_t start, int64_t len); > > int qemu_lock_fd_test(int fd, int64_t start, int64_t len, bool exclusive); > > bool qemu_has_ofd_lock(void); > > +bool qemu_has_file_lock(int fd); > > #endif > > #if defined(__HAIKU__) && defined(__i386__) > > diff --git a/util/osdep.c b/util/osdep.c > > index 66d01b9160..dee1f076da 100644 > > --- a/util/osdep.c > > +++ b/util/osdep.c > > @@ -225,6 +225,20 @@ static void qemu_probe_lock_ops(void) > > } > > } > > +bool qemu_has_file_lock(int fd) > > +{ > > + int ret; > > + struct flock fl = { > > + .l_whence = SEEK_SET, > > + .l_start = 0, > > + .l_len = 0, > > + .l_type = F_WRLCK, > > + }; > > + > > + ret = fcntl(fd, F_GETLK, &fl); > > I think we need > > qemu_probe_lock_ops(); > ret = fcntl(fd, fcntl_op_getlk, &fl); > > pattern instead, like in qemu_lock_fd_test(). Otherwise, what we check may differ with what we are going to use. No, we explicitly do *not* want that. This function is *only* about checking whether traditional fcntl locks work or not on this specific file handle. Support for OFD locks is a separate check, and its result applies system wide. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|