From patchwork Mon May 8 01:17:12 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Luis Chamberlain X-Patchwork-Id: 13233986 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 661E2C77B7C for ; Mon, 8 May 2023 01:17:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232273AbjEHBRn (ORCPT ); Sun, 7 May 2023 21:17:43 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:37080 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232166AbjEHBRg (ORCPT ); Sun, 7 May 2023 21:17:36 -0400 Received: from bombadil.infradead.org (bombadil.infradead.org [IPv6:2607:7c80:54:3::133]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9AA9F4698; Sun, 7 May 2023 18:17:34 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=Sender:Content-Transfer-Encoding: MIME-Version:References:In-Reply-To:Message-Id:Date:Subject:Cc:To:From: Reply-To:Content-Type:Content-ID:Content-Description; bh=kBqqORDo5ZDeQubFLWt/Ze74JpFUmhricU9x7bL4UTQ=; b=h6trr0sC7qNp8uHXMnyvLn/Jan KuDgv/M0kH9YyEtN4IrpZFJUwK1NTw7h9L9jpf6EUCv1sZrwsCz+lMaZc+aH4aVNg8nnH0ma+sRJB ylWv14+go3Hzo+xUegcVMxLMqWhtgrChqPj+Aev5wfVx5RXmksHRgOxgoXLwDVIM45xCWi+pFwiwe LMLVkKI+DfSF+H3RTMBIVKVxTX8GXCADgFs3jMf8WRo9048F/FFDL9WYOYaPNRePTBmbOVNGzWUnz aZ6/KzqhZ9w8lM7pexORnK8MU4U5TMyUCnGr2uR933XScy2l6La3PNEao+QMr6LHDIgRHZyNVQFuY lycRanxA==; Received: from mcgrof by bombadil.infradead.org with local (Exim 4.96 #2 (Red Hat Linux)) id 1pvpV7-00GvYy-2e; Mon, 08 May 2023 01:17:17 +0000 From: Luis Chamberlain To: hch@infradead.org, djwong@kernel.org, sandeen@sandeen.net, song@kernel.org, rafael@kernel.org, gregkh@linuxfoundation.org, viro@zeniv.linux.org.uk, jack@suse.cz, jikos@kernel.org, bvanassche@acm.org, ebiederm@xmission.com Cc: mchehab@kernel.org, keescook@chromium.org, p.raghav@samsung.com, da.gomez@samsung.com, linux-fsdevel@vger.kernel.org, kernel@tuxforce.de, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, Luis Chamberlain Subject: [PATCH 1/6] fs: unify locking semantics for fs freeze / thaw Date: Sun, 7 May 2023 18:17:12 -0700 Message-Id: <20230508011717.4034511-2-mcgrof@kernel.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20230508011717.4034511-1-mcgrof@kernel.org> References: <20230508011717.4034511-1-mcgrof@kernel.org> MIME-Version: 1.0 Sender: Luis Chamberlain Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Right now freeze_super() and thaw_super() are called with different locking contexts. To expand on this is messy, so just unify the requirement to require grabbing an active reference and keep the superblock locked. Suggested-by: Christoph Hellwig Signed-off-by: Luis Chamberlain --- block/bdev.c | 5 +++- fs/f2fs/gc.c | 5 ++++ fs/gfs2/super.c | 9 +++++-- fs/gfs2/sys.c | 6 +++++ fs/gfs2/util.c | 5 ++++ fs/ioctl.c | 12 ++++++++-- fs/super.c | 62 ++++++++++++++++++------------------------------- 7 files changed, 60 insertions(+), 44 deletions(-) diff --git a/block/bdev.c b/block/bdev.c index 21c63bfef323..dc54a2a1c46e 100644 --- a/block/bdev.c +++ b/block/bdev.c @@ -251,7 +251,7 @@ int freeze_bdev(struct block_device *bdev) error = sb->s_op->freeze_super(sb); else error = freeze_super(sb); - deactivate_super(sb); + deactivate_locked_super(sb); if (error) { bdev->bd_fsfreeze_count--; @@ -289,6 +289,8 @@ int thaw_bdev(struct block_device *bdev) sb = bdev->bd_fsfreeze_sb; if (!sb) goto out; + if (!get_active_super(bdev)) + goto out; if (sb->s_op->thaw_super) error = sb->s_op->thaw_super(sb); @@ -298,6 +300,7 @@ int thaw_bdev(struct block_device *bdev) bdev->bd_fsfreeze_count++; else bdev->bd_fsfreeze_sb = NULL; + deactivate_locked_super(sb); out: mutex_unlock(&bdev->bd_fsfreeze_mutex); return error; diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c index 61c5f9d26018..e31d6791d3e3 100644 --- a/fs/f2fs/gc.c +++ b/fs/f2fs/gc.c @@ -2166,7 +2166,10 @@ int f2fs_resize_fs(struct f2fs_sb_info *sbi, __u64 block_count) if (err) return err; + if (!get_active_super(sbi->sb->s_bdev)) + return -ENOTTY; freeze_super(sbi->sb); + f2fs_down_write(&sbi->gc_lock); f2fs_down_write(&sbi->cp_global_sem); @@ -2217,6 +2220,8 @@ int f2fs_resize_fs(struct f2fs_sb_info *sbi, __u64 block_count) out_err: f2fs_up_write(&sbi->cp_global_sem); f2fs_up_write(&sbi->gc_lock); + /* We use the same active reference from freeze */ thaw_super(sbi->sb); + deactivate_locked_super(sbi->sb); return err; } diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c index 5eed8c237500..e57cb593e2f3 100644 --- a/fs/gfs2/super.c +++ b/fs/gfs2/super.c @@ -676,7 +676,12 @@ void gfs2_freeze_func(struct work_struct *work) struct gfs2_sbd *sdp = container_of(work, struct gfs2_sbd, sd_freeze_work); struct super_block *sb = sdp->sd_vfs; - atomic_inc(&sb->s_active); + if (!get_active_super(sb->s_bdev)) { + fs_info(sdp, "GFS2: couldn't grap super for thaw for filesystem\n"); + gfs2_assert_withdraw(sdp, 0); + return; + } + error = gfs2_freeze_lock(sdp, &freeze_gh, 0); if (error) { gfs2_assert_withdraw(sdp, 0); @@ -690,7 +695,7 @@ void gfs2_freeze_func(struct work_struct *work) } gfs2_freeze_unlock(&freeze_gh); } - deactivate_super(sb); + deactivate_locked_super(sb); clear_bit_unlock(SDF_FS_FROZEN, &sdp->sd_flags); wake_up_bit(&sdp->sd_flags, SDF_FS_FROZEN); return; diff --git a/fs/gfs2/sys.c b/fs/gfs2/sys.c index 454dc2ff8b5e..cbb71c3520c0 100644 --- a/fs/gfs2/sys.c +++ b/fs/gfs2/sys.c @@ -164,6 +164,9 @@ static ssize_t freeze_store(struct gfs2_sbd *sdp, const char *buf, size_t len) if (!capable(CAP_SYS_ADMIN)) return -EPERM; + if (!get_active_super(sb->s_bdev)) + return -ENOTTY; + switch (n) { case 0: error = thaw_super(sdp->sd_vfs); @@ -172,9 +175,12 @@ static ssize_t freeze_store(struct gfs2_sbd *sdp, const char *buf, size_t len) error = freeze_super(sdp->sd_vfs); break; default: + deactivate_locked_super(sb); return -EINVAL; } + deactivate_locked_super(sb); + if (error) { fs_warn(sdp, "freeze %d error %d\n", n, error); return error; diff --git a/fs/gfs2/util.c b/fs/gfs2/util.c index 7a6aeffcdf5c..3a0cd5e9ad84 100644 --- a/fs/gfs2/util.c +++ b/fs/gfs2/util.c @@ -345,10 +345,15 @@ int gfs2_withdraw(struct gfs2_sbd *sdp) set_bit(SDF_WITHDRAW_IN_PROG, &sdp->sd_flags); if (sdp->sd_args.ar_errors == GFS2_ERRORS_WITHDRAW) { + if (!get_active_super(sb->s_bdev)) { + fs_err(sdp, "could not grab super on withdraw for file system\n"); + return -1; + } fs_err(sdp, "about to withdraw this file system\n"); BUG_ON(sdp->sd_args.ar_debug); signal_our_withdraw(sdp); + deactivate_locked_super(sb); kobject_uevent(&sdp->sd_kobj, KOBJ_OFFLINE); diff --git a/fs/ioctl.c b/fs/ioctl.c index 5b2481cd4750..1d20af762e0d 100644 --- a/fs/ioctl.c +++ b/fs/ioctl.c @@ -386,6 +386,7 @@ static int ioctl_fioasync(unsigned int fd, struct file *filp, static int ioctl_fsfreeze(struct file *filp) { struct super_block *sb = file_inode(filp)->i_sb; + int ret; if (!ns_capable(sb->s_user_ns, CAP_SYS_ADMIN)) return -EPERM; @@ -394,10 +395,17 @@ static int ioctl_fsfreeze(struct file *filp) if (sb->s_op->freeze_fs == NULL && sb->s_op->freeze_super == NULL) return -EOPNOTSUPP; + if (!get_active_super(sb->s_bdev)) + return -ENOTTY; + /* Freeze */ if (sb->s_op->freeze_super) - return sb->s_op->freeze_super(sb); - return freeze_super(sb); + ret = sb->s_op->freeze_super(sb); + ret = freeze_super(sb); + + deactivate_locked_super(sb); + + return ret; } static int ioctl_fsthaw(struct file *filp) diff --git a/fs/super.c b/fs/super.c index 34afe411cf2b..0e9d48846684 100644 --- a/fs/super.c +++ b/fs/super.c @@ -39,8 +39,6 @@ #include #include "internal.h" -static int thaw_super_locked(struct super_block *sb); - static LIST_HEAD(super_blocks); static DEFINE_SPINLOCK(sb_lock); @@ -851,13 +849,13 @@ struct super_block *get_active_super(struct block_device *bdev) if (sb->s_bdev == bdev) { if (!grab_super(sb)) goto restart; - up_write(&sb->s_umount); return sb; } } spin_unlock(&sb_lock); return NULL; } +EXPORT_SYMBOL_GPL(get_active_super); struct super_block *user_get_super(dev_t dev, bool excl) { @@ -1024,13 +1022,13 @@ void emergency_remount(void) static void do_thaw_all_callback(struct super_block *sb) { - down_write(&sb->s_umount); + if (!get_active_super(sb->s_bdev)) + return; if (sb->s_root && sb->s_flags & SB_BORN) { emergency_thaw_bdev(sb); - thaw_super_locked(sb); - } else { - up_write(&sb->s_umount); + thaw_super(sb); } + deactivate_locked_super(sb); } static void do_thaw_all(struct work_struct *work) @@ -1636,10 +1634,13 @@ static void sb_freeze_unlock(struct super_block *sb, int level) } /** - * freeze_super - lock the filesystem and force it into a consistent state + * freeze_super - force a filesystem backed by a block device into a consistent state * @sb: the super to lock * - * Syncs the super to make sure the filesystem is consistent and calls the fs's + * Used by filesystems and the kernel to freeze a fileystem backed by a block + * device into a consistent state. Callers must use get_active_super(bdev) to + * lock the @sb and when done must unlock it with deactivate_locked_super(). + * Syncs the filesystem backed by the @sb and calls the filesystem's optional * freeze_fs. Subsequent calls to this without first thawing the fs will return * -EBUSY. * @@ -1672,22 +1673,15 @@ int freeze_super(struct super_block *sb) { int ret; - atomic_inc(&sb->s_active); - down_write(&sb->s_umount); - if (sb->s_writers.frozen != SB_UNFROZEN) { - deactivate_locked_super(sb); + if (sb->s_writers.frozen != SB_UNFROZEN) return -EBUSY; - } - if (!(sb->s_flags & SB_BORN)) { - up_write(&sb->s_umount); + if (!(sb->s_flags & SB_BORN)) return 0; /* sic - it's "nothing to do" */ - } if (sb_rdonly(sb)) { /* Nothing to do really... */ sb->s_writers.frozen = SB_FREEZE_COMPLETE; - up_write(&sb->s_umount); return 0; } @@ -1707,7 +1701,6 @@ int freeze_super(struct super_block *sb) sb->s_writers.frozen = SB_UNFROZEN; sb_freeze_unlock(sb, SB_FREEZE_PAGEFAULT); wake_up(&sb->s_writers.wait_unfrozen); - deactivate_locked_super(sb); return ret; } @@ -1723,7 +1716,6 @@ int freeze_super(struct super_block *sb) sb->s_writers.frozen = SB_UNFROZEN; sb_freeze_unlock(sb, SB_FREEZE_FS); wake_up(&sb->s_writers.wait_unfrozen); - deactivate_locked_super(sb); return ret; } } @@ -1733,19 +1725,25 @@ int freeze_super(struct super_block *sb) */ sb->s_writers.frozen = SB_FREEZE_COMPLETE; lockdep_sb_freeze_release(sb); - up_write(&sb->s_umount); return 0; } EXPORT_SYMBOL(freeze_super); -static int thaw_super_locked(struct super_block *sb) +/** + * thaw_super -- unlock a filesystem backed by a block device + * @sb: the super to thaw + * + * Used by filesystems and the kernel to thaw a fileystem backed by a block + * device. Callers must use get_active_super(bdev) to lock the @sb and when + * done must unlock it with deactivate_locked_super(). Once done, this marks + * the filesystem as writeable. + */ +int thaw_super(struct super_block *sb) { int error; - if (sb->s_writers.frozen != SB_FREEZE_COMPLETE) { - up_write(&sb->s_umount); + if (sb->s_writers.frozen != SB_FREEZE_COMPLETE) return -EINVAL; - } if (sb_rdonly(sb)) { sb->s_writers.frozen = SB_UNFROZEN; @@ -1760,7 +1758,6 @@ static int thaw_super_locked(struct super_block *sb) printk(KERN_ERR "VFS:Filesystem thaw failed\n"); lockdep_sb_freeze_release(sb); - up_write(&sb->s_umount); return error; } } @@ -1769,21 +1766,8 @@ static int thaw_super_locked(struct super_block *sb) sb_freeze_unlock(sb, SB_FREEZE_FS); out: wake_up(&sb->s_writers.wait_unfrozen); - deactivate_locked_super(sb); return 0; } - -/** - * thaw_super -- unlock filesystem - * @sb: the super to thaw - * - * Unlocks the filesystem and marks it writeable again after freeze_super(). - */ -int thaw_super(struct super_block *sb) -{ - down_write(&sb->s_umount); - return thaw_super_locked(sb); -} EXPORT_SYMBOL(thaw_super); /*