From patchwork Mon Jun 12 03:15:22 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Darrick J. Wong" X-Patchwork-Id: 13275415 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 A179CC7EE37 for ; Mon, 12 Jun 2023 03:15:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234358AbjFLDP2 (ORCPT ); Sun, 11 Jun 2023 23:15:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49772 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233567AbjFLDP0 (ORCPT ); Sun, 11 Jun 2023 23:15:26 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 45D2CBB; Sun, 11 Jun 2023 20:15:24 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id C075261DB4; Mon, 12 Jun 2023 03:15:23 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 295FCC433D2; Mon, 12 Jun 2023 03:15:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1686539723; bh=i25gJ8aHvZCp1kE9b2V8twq6peEngvat0QHP4rshTvc=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=mhRGMvIbQjwxwHq/auw8TCDNGzSlphgclyZBKeEQEBkQYhTtcRTmkRg2gEXvGtPeU OCoE6I8HUIaQddYUWWL65i+pEc1UPJY2VG2/UBBYxluSGog8FIwUyRzLLOiOXroPfs 8tjJ6+VG1P98ZgIxrzfr39k9eXyQI+FTdxhtfyk2dsUVRhxjzZx6ys7fsM1gQ9pOaY W5w1l1rVwf1bJAmwF0PXSPckzmzFDzxyRfzQVBidoWIM+lzDG3uezseVnOrn1iZRlZ Uduy2TfK0oRobEaqxTR5G8R7ILSRv3TpyahKKBKMGN4m3DYmeeAgffuNvgt/sO5QbO oXGZrv62DYMdA== Subject: [PATCH 1/3] fs: distinguish between user initiated freeze and kernel initiated freeze From: "Darrick J. Wong" To: djwong@kernel.org Cc: mcgrof@kernel.org, jack@suse.cz, hch@infradead.org, ruansy.fnst@fujitsu.com, linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, mcgrof@kernel.org, jack@suse.cz, hch@infradead.org, ruansy.fnst@fujitsu.com Date: Sun, 11 Jun 2023 20:15:22 -0700 Message-ID: <168653972267.755178.18328538743442432037.stgit@frogsfrogsfrogs> In-Reply-To: <168653971691.755178.4003354804404850534.stgit@frogsfrogsfrogs> References: <168653971691.755178.4003354804404850534.stgit@frogsfrogsfrogs> User-Agent: StGit/0.19 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org From: Darrick J. Wong Userspace can freeze a filesystem using the FIFREEZE ioctl or by suspending the block device; this state persists until userspace thaws the filesystem with the FITHAW ioctl or resuming the block device. Since commit 18e9e5104fcd ("Introduce freeze_super and thaw_super for the fsfreeze ioctl") we only allow the first freeze command to succeed. The kernel may decide that it is necessary to freeze a filesystem for its own internal purposes, such as suspends in progress, filesystem fsck activities, or quiescing a device prior to removal. Userspace thaw commands must never break a kernel freeze, and kernel thaw commands shouldn't undo userspace's freeze command. Introduce a couple of freeze holder flags and wire it into the sb_writers state. One kernel and one userspace freeze are allowed to coexist at the same time; the filesystem will not thaw until both are lifted. I wonder if the f2fs/gfs2 code should be using a kernel freeze here, but for now we'll use FREEZE_HOLDER_USERSPACE to preserve existing behaviors. Cc: mcgrof@kernel.org Cc: jack@suse.cz Cc: hch@infradead.org Cc: ruansy.fnst@fujitsu.com Signed-off-by: Darrick J. Wong Reviewed-by: Christoph Hellwig --- Documentation/filesystems/vfs.rst | 4 +- block/bdev.c | 8 ++-- fs/f2fs/gc.c | 4 +- fs/gfs2/glops.c | 2 - fs/gfs2/super.c | 6 +-- fs/gfs2/sys.c | 4 +- fs/gfs2/util.c | 2 - fs/ioctl.c | 8 ++-- fs/super.c | 79 +++++++++++++++++++++++++++++++++---- include/linux/fs.h | 15 +++++-- 10 files changed, 100 insertions(+), 32 deletions(-) diff --git a/Documentation/filesystems/vfs.rst b/Documentation/filesystems/vfs.rst index 769be5230210..41cf2a56cbca 100644 --- a/Documentation/filesystems/vfs.rst +++ b/Documentation/filesystems/vfs.rst @@ -260,9 +260,9 @@ filesystem. The following members are defined: void (*evict_inode) (struct inode *); void (*put_super) (struct super_block *); int (*sync_fs)(struct super_block *sb, int wait); - int (*freeze_super) (struct super_block *); + int (*freeze_super) (struct super_block *, enum freeze_holder who); int (*freeze_fs) (struct super_block *); - int (*thaw_super) (struct super_block *); + int (*thaw_super) (struct super_block *, enum freeze_wholder who); int (*unfreeze_fs) (struct super_block *); int (*statfs) (struct dentry *, struct kstatfs *); int (*remount_fs) (struct super_block *, int *, char *); diff --git a/block/bdev.c b/block/bdev.c index 21c63bfef323..e8032c5beae0 100644 --- a/block/bdev.c +++ b/block/bdev.c @@ -248,9 +248,9 @@ int freeze_bdev(struct block_device *bdev) if (!sb) goto sync; if (sb->s_op->freeze_super) - error = sb->s_op->freeze_super(sb); + error = sb->s_op->freeze_super(sb, FREEZE_HOLDER_USERSPACE); else - error = freeze_super(sb); + error = freeze_super(sb, FREEZE_HOLDER_USERSPACE); deactivate_super(sb); if (error) { @@ -291,9 +291,9 @@ int thaw_bdev(struct block_device *bdev) goto out; if (sb->s_op->thaw_super) - error = sb->s_op->thaw_super(sb); + error = sb->s_op->thaw_super(sb, FREEZE_HOLDER_USERSPACE); else - error = thaw_super(sb); + error = thaw_super(sb, FREEZE_HOLDER_USERSPACE); if (error) bdev->bd_fsfreeze_count++; else diff --git a/fs/f2fs/gc.c b/fs/f2fs/gc.c index 61c5f9d26018..bca4e75c14e0 100644 --- a/fs/f2fs/gc.c +++ b/fs/f2fs/gc.c @@ -2166,7 +2166,7 @@ int f2fs_resize_fs(struct f2fs_sb_info *sbi, __u64 block_count) if (err) return err; - freeze_super(sbi->sb); + freeze_super(sbi->sb, FREEZE_HOLDER_USERSPACE); f2fs_down_write(&sbi->gc_lock); f2fs_down_write(&sbi->cp_global_sem); @@ -2217,6 +2217,6 @@ 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); - thaw_super(sbi->sb); + thaw_super(sbi->sb, FREEZE_HOLDER_USERSPACE); return err; } diff --git a/fs/gfs2/glops.c b/fs/gfs2/glops.c index 01d433ed6ce7..6bffb7609d01 100644 --- a/fs/gfs2/glops.c +++ b/fs/gfs2/glops.c @@ -584,7 +584,7 @@ static int freeze_go_sync(struct gfs2_glock *gl) if (gl->gl_state == LM_ST_SHARED && !gfs2_withdrawn(sdp) && !test_bit(SDF_NORECOVERY, &sdp->sd_flags)) { atomic_set(&sdp->sd_freeze_state, SFS_STARTING_FREEZE); - error = freeze_super(sdp->sd_vfs); + error = freeze_super(sdp->sd_vfs, FREEZE_HOLDER_USERSPACE); if (error) { fs_info(sdp, "GFS2: couldn't freeze filesystem: %d\n", error); diff --git a/fs/gfs2/super.c b/fs/gfs2/super.c index a84bf6444bba..3965b00a7503 100644 --- a/fs/gfs2/super.c +++ b/fs/gfs2/super.c @@ -682,7 +682,7 @@ void gfs2_freeze_func(struct work_struct *work) gfs2_assert_withdraw(sdp, 0); } else { atomic_set(&sdp->sd_freeze_state, SFS_UNFROZEN); - error = thaw_super(sb); + error = thaw_super(sb, FREEZE_HOLDER_USERSPACE); if (error) { fs_info(sdp, "GFS2: couldn't thaw filesystem: %d\n", error); @@ -702,7 +702,7 @@ void gfs2_freeze_func(struct work_struct *work) * */ -static int gfs2_freeze(struct super_block *sb) +static int gfs2_freeze(struct super_block *sb, enum freeze_holder who) { struct gfs2_sbd *sdp = sb->s_fs_info; int error; @@ -747,7 +747,7 @@ static int gfs2_freeze(struct super_block *sb) * */ -static int gfs2_unfreeze(struct super_block *sb) +static int gfs2_unfreeze(struct super_block *sb, enum freeze_holder who) { struct gfs2_sbd *sdp = sb->s_fs_info; diff --git a/fs/gfs2/sys.c b/fs/gfs2/sys.c index 454dc2ff8b5e..9d04a2907869 100644 --- a/fs/gfs2/sys.c +++ b/fs/gfs2/sys.c @@ -166,10 +166,10 @@ static ssize_t freeze_store(struct gfs2_sbd *sdp, const char *buf, size_t len) switch (n) { case 0: - error = thaw_super(sdp->sd_vfs); + error = thaw_super(sdp->sd_vfs, FREEZE_HOLDER_USERSPACE); break; case 1: - error = freeze_super(sdp->sd_vfs); + error = freeze_super(sdp->sd_vfs, FREEZE_HOLDER_USERSPACE); break; default: return -EINVAL; diff --git a/fs/gfs2/util.c b/fs/gfs2/util.c index 7a6aeffcdf5c..357457b7c5b3 100644 --- a/fs/gfs2/util.c +++ b/fs/gfs2/util.c @@ -191,7 +191,7 @@ static void signal_our_withdraw(struct gfs2_sbd *sdp) /* Make sure gfs2_unfreeze works if partially-frozen */ flush_work(&sdp->sd_freeze_work); atomic_set(&sdp->sd_freeze_state, SFS_FROZEN); - thaw_super(sdp->sd_vfs); + thaw_super(sdp->sd_vfs, FREEZE_HOLDER_USERSPACE); } else { wait_on_bit(&i_gl->gl_flags, GLF_DEMOTE, TASK_UNINTERRUPTIBLE); diff --git a/fs/ioctl.c b/fs/ioctl.c index 5b2481cd4750..a56cbceedcd1 100644 --- a/fs/ioctl.c +++ b/fs/ioctl.c @@ -396,8 +396,8 @@ static int ioctl_fsfreeze(struct file *filp) /* Freeze */ if (sb->s_op->freeze_super) - return sb->s_op->freeze_super(sb); - return freeze_super(sb); + return sb->s_op->freeze_super(sb, FREEZE_HOLDER_USERSPACE); + return freeze_super(sb, FREEZE_HOLDER_USERSPACE); } static int ioctl_fsthaw(struct file *filp) @@ -409,8 +409,8 @@ static int ioctl_fsthaw(struct file *filp) /* Thaw */ if (sb->s_op->thaw_super) - return sb->s_op->thaw_super(sb); - return thaw_super(sb); + return sb->s_op->thaw_super(sb, FREEZE_HOLDER_USERSPACE); + return thaw_super(sb, FREEZE_HOLDER_USERSPACE); } static int ioctl_file_dedupe_range(struct file *file, diff --git a/fs/super.c b/fs/super.c index 34afe411cf2b..36adccecc828 100644 --- a/fs/super.c +++ b/fs/super.c @@ -39,7 +39,7 @@ #include #include "internal.h" -static int thaw_super_locked(struct super_block *sb); +static int thaw_super_locked(struct super_block *sb, enum freeze_holder who); static LIST_HEAD(super_blocks); static DEFINE_SPINLOCK(sb_lock); @@ -1027,7 +1027,7 @@ static void do_thaw_all_callback(struct super_block *sb) down_write(&sb->s_umount); if (sb->s_root && sb->s_flags & SB_BORN) { emergency_thaw_bdev(sb); - thaw_super_locked(sb); + thaw_super_locked(sb, FREEZE_HOLDER_USERSPACE); } else { up_write(&sb->s_umount); } @@ -1635,14 +1635,34 @@ static void sb_freeze_unlock(struct super_block *sb, int level) percpu_up_write(sb->s_writers.rw_sem + level); } +static int freeze_frozen_super(struct super_block *sb, enum freeze_holder who) +{ + /* Someone else already holds this type of freeze */ + if (sb->s_writers.freeze_holders & who) + return -EBUSY; + + WARN_ON(sb->s_writers.freeze_holders == 0); + + sb->s_writers.freeze_holders |= who; + return 0; +} + /** * freeze_super - lock the filesystem and force it into a consistent state * @sb: the super to lock + * @who: FREEZE_HOLDER_USERSPACE if userspace wants to freeze the fs; + * FREEZE_HOLDER_KERNEL if the kernel wants to freeze it * * Syncs the super to make sure the filesystem is consistent and calls the fs's - * freeze_fs. Subsequent calls to this without first thawing the fs will return + * freeze_fs. Subsequent calls to this without first thawing the fs may return * -EBUSY. * + * The @who argument distinguishes between the kernel and userspace trying to + * freeze the filesystem. Although there cannot be multiple kernel freezes or + * multiple userspace freezes in effect at any given time, the kernel and + * userspace can both hold a filesystem frozen. The filesystem remains frozen + * until there are no kernel or userspace freezes in effect. + * * During this function, sb->s_writers.frozen goes through these values: * * SB_UNFROZEN: File system is normal, all writes progress as usual. @@ -1668,12 +1688,19 @@ static void sb_freeze_unlock(struct super_block *sb, int level) * * sb->s_writers.frozen is protected by sb->s_umount. */ -int freeze_super(struct super_block *sb) +int freeze_super(struct super_block *sb, enum freeze_holder who) { int ret; atomic_inc(&sb->s_active); down_write(&sb->s_umount); + + if (sb->s_writers.frozen == SB_FREEZE_COMPLETE) { + ret = freeze_frozen_super(sb, who); + deactivate_locked_super(sb); + return ret; + } + if (sb->s_writers.frozen != SB_UNFROZEN) { deactivate_locked_super(sb); return -EBUSY; @@ -1684,8 +1711,10 @@ int freeze_super(struct super_block *sb) return 0; /* sic - it's "nothing to do" */ } + if (sb_rdonly(sb)) { /* Nothing to do really... */ + sb->s_writers.freeze_holders |= who; sb->s_writers.frozen = SB_FREEZE_COMPLETE; up_write(&sb->s_umount); return 0; @@ -1731,6 +1760,7 @@ int freeze_super(struct super_block *sb) * For debugging purposes so that fs can warn if it sees write activity * when frozen is set to SB_FREEZE_COMPLETE, and for thaw_super(). */ + sb->s_writers.freeze_holders |= who; sb->s_writers.frozen = SB_FREEZE_COMPLETE; lockdep_sb_freeze_release(sb); up_write(&sb->s_umount); @@ -1738,16 +1768,47 @@ int freeze_super(struct super_block *sb) } EXPORT_SYMBOL(freeze_super); -static int thaw_super_locked(struct super_block *sb) +static int try_thaw_shared_super(struct super_block *sb, enum freeze_holder who) +{ + /* Freeze is not held by this type? */ + if (!(sb->s_writers.freeze_holders & who)) + return -EINVAL; + + /* Also frozen for someone else? */ + if (sb->s_writers.freeze_holders & ~who) { + sb->s_writers.freeze_holders &= ~who; + return 0; + } + + /* Magic value to proceed with thaw */ + return 1; +} + +/* + * Undoes the effect of a freeze_super_locked call. If the filesystem is + * frozen both by userspace and the kernel, a thaw call from either source + * removes that state without releasing the other state or unlocking the + * filesystem. + */ +static int thaw_super_locked(struct super_block *sb, enum freeze_holder who) { int error; + if (sb->s_writers.frozen == SB_FREEZE_COMPLETE) { + error = try_thaw_shared_super(sb, who); + if (error != 1) { + up_write(&sb->s_umount); + return error; + } + } + if (sb->s_writers.frozen != SB_FREEZE_COMPLETE) { up_write(&sb->s_umount); return -EINVAL; } if (sb_rdonly(sb)) { + sb->s_writers.freeze_holders &= ~who; sb->s_writers.frozen = SB_UNFROZEN; goto out; } @@ -1765,6 +1826,7 @@ static int thaw_super_locked(struct super_block *sb) } } + sb->s_writers.freeze_holders &= ~who; sb->s_writers.frozen = SB_UNFROZEN; sb_freeze_unlock(sb, SB_FREEZE_FS); out: @@ -1777,12 +1839,13 @@ static int thaw_super_locked(struct super_block *sb) * thaw_super -- unlock filesystem * @sb: the super to thaw * - * Unlocks the filesystem and marks it writeable again after freeze_super(). + * Unlocks the filesystem and marks it writeable again after freeze_super() + * if there are no remaining freezes on the filesystem. */ -int thaw_super(struct super_block *sb) +int thaw_super(struct super_block *sb, enum freeze_holder who) { down_write(&sb->s_umount); - return thaw_super_locked(sb); + return thaw_super_locked(sb, who); } EXPORT_SYMBOL(thaw_super); diff --git a/include/linux/fs.h b/include/linux/fs.h index 133f0640fb24..c58a560569b3 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1145,7 +1145,8 @@ enum { #define SB_FREEZE_LEVELS (SB_FREEZE_COMPLETE - 1) struct sb_writers { - int frozen; /* Is sb frozen? */ + unsigned short frozen; /* Is sb frozen? */ + unsigned short freeze_holders; /* Who froze fs? */ wait_queue_head_t wait_unfrozen; /* wait for thaw */ struct percpu_rw_semaphore rw_sem[SB_FREEZE_LEVELS]; }; @@ -1899,6 +1900,10 @@ extern loff_t vfs_dedupe_file_range_one(struct file *src_file, loff_t src_pos, struct file *dst_file, loff_t dst_pos, loff_t len, unsigned int remap_flags); +enum freeze_holder { + FREEZE_HOLDER_KERNEL = (1U << 0), + FREEZE_HOLDER_USERSPACE = (1U << 1), +}; struct super_operations { struct inode *(*alloc_inode)(struct super_block *sb); @@ -1911,9 +1916,9 @@ struct super_operations { void (*evict_inode) (struct inode *); void (*put_super) (struct super_block *); int (*sync_fs)(struct super_block *sb, int wait); - int (*freeze_super) (struct super_block *); + int (*freeze_super) (struct super_block *, enum freeze_holder who); int (*freeze_fs) (struct super_block *); - int (*thaw_super) (struct super_block *); + int (*thaw_super) (struct super_block *, enum freeze_holder who); int (*unfreeze_fs) (struct super_block *); int (*statfs) (struct dentry *, struct kstatfs *); int (*remount_fs) (struct super_block *, int *, char *); @@ -2286,8 +2291,8 @@ extern int unregister_filesystem(struct file_system_type *); extern int vfs_statfs(const struct path *, struct kstatfs *); extern int user_statfs(const char __user *, struct kstatfs *); extern int fd_statfs(int, struct kstatfs *); -extern int freeze_super(struct super_block *super); -extern int thaw_super(struct super_block *super); +extern int freeze_super(struct super_block *super, enum freeze_holder who); +extern int thaw_super(struct super_block *super, enum freeze_holder who); extern __printf(2, 3) int super_setup_bdi_name(struct super_block *sb, char *fmt, ...); extern int super_setup_bdi(struct super_block *sb); From patchwork Mon Jun 12 03:15:28 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Darrick J. Wong" X-Patchwork-Id: 13275419 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 BB1EFC7EE2E for ; Mon, 12 Jun 2023 03:16:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234535AbjFLDQI (ORCPT ); Sun, 11 Jun 2023 23:16:08 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49804 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234386AbjFLDPa (ORCPT ); Sun, 11 Jun 2023 23:15:30 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DF8E513D; Sun, 11 Jun 2023 20:15:29 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 7449F61DDD; Mon, 12 Jun 2023 03:15:29 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id CE226C4339C; Mon, 12 Jun 2023 03:15:28 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1686539728; bh=6S3I2JdtbBod470Y373FgEPjrmviIhpS+7yicePNWWg=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=oxCtUWovCdToUHoIeCdsgpaeuGpFMUnlvphWpPr4Fj0RNQTrLPPwg5ITLSm/nPwdZ 5MT9V6ykwKFCqzEuP0UIEKatQNmz8bBXT+THnSlyJiGqXtz09C7+/C9heUqO3D/H4t PCx497R+XwYO+abnYb3altfi1TS0AlxXZu6MX6My+deBCfLDOnZveXnDcvoYQHJrqz 73bpYOjzPPvvZV2/P76SNL1l1KpuwXT0ms5a8uNMqwyFhlTzH35tLI2kQahjnM+aa+ jPw7pNqu+JL9+AzyEsq+u28au2P/Pg22OytDTrqgS6TYVdYpZJMDroHe5vQp73lj0A s/8cK0NV5gP3g== Subject: [PATCH 2/3] fs: wait for partially frozen filesystems From: "Darrick J. Wong" To: djwong@kernel.org Cc: linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, mcgrof@kernel.org, jack@suse.cz, hch@infradead.org, ruansy.fnst@fujitsu.com Date: Sun, 11 Jun 2023 20:15:28 -0700 Message-ID: <168653972832.755178.18389114450766371923.stgit@frogsfrogsfrogs> In-Reply-To: <168653971691.755178.4003354804404850534.stgit@frogsfrogsfrogs> References: <168653971691.755178.4003354804404850534.stgit@frogsfrogsfrogs> User-Agent: StGit/0.19 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org From: Darrick J. Wong Jan Kara suggested that when one thread is in the middle of freezing a filesystem, another thread trying to freeze the same fs but with a different freeze_holder should wait until the freezer reaches either end state (UNFROZEN or COMPLETE) instead of returning EBUSY immediately. Plumb in the extra coded needed to wait for the fs freezer to reach an end state and try the freeze again. Signed-off-by: Darrick J. Wong --- fs/super.c | 27 +++++++++++++++++++++++++-- 1 file changed, 25 insertions(+), 2 deletions(-) diff --git a/fs/super.c b/fs/super.c index 36adccecc828..151e0eeff2c2 100644 --- a/fs/super.c +++ b/fs/super.c @@ -1647,6 +1647,15 @@ static int freeze_frozen_super(struct super_block *sb, enum freeze_holder who) return 0; } +static void wait_for_partially_frozen(struct super_block *sb) +{ + up_write(&sb->s_umount); + wait_var_event(&sb->s_writers.frozen, + sb->s_writers.frozen == SB_UNFROZEN || + sb->s_writers.frozen == SB_FREEZE_COMPLETE); + down_write(&sb->s_umount); +} + /** * freeze_super - lock the filesystem and force it into a consistent state * @sb: the super to lock @@ -1690,11 +1699,13 @@ static int freeze_frozen_super(struct super_block *sb, enum freeze_holder who) */ int freeze_super(struct super_block *sb, enum freeze_holder who) { + bool try_again = true; int ret; atomic_inc(&sb->s_active); down_write(&sb->s_umount); +retry: if (sb->s_writers.frozen == SB_FREEZE_COMPLETE) { ret = freeze_frozen_super(sb, who); deactivate_locked_super(sb); @@ -1702,8 +1713,14 @@ int freeze_super(struct super_block *sb, enum freeze_holder who) } if (sb->s_writers.frozen != SB_UNFROZEN) { - deactivate_locked_super(sb); - return -EBUSY; + if (!try_again) { + deactivate_locked_super(sb); + return -EBUSY; + } + + wait_for_partially_frozen(sb); + try_again = false; + goto retry; } if (!(sb->s_flags & SB_BORN)) { @@ -1716,6 +1733,7 @@ int freeze_super(struct super_block *sb, enum freeze_holder who) /* Nothing to do really... */ sb->s_writers.freeze_holders |= who; sb->s_writers.frozen = SB_FREEZE_COMPLETE; + wake_up_var(&sb->s_writers.frozen); up_write(&sb->s_umount); return 0; } @@ -1736,6 +1754,7 @@ int freeze_super(struct super_block *sb, enum freeze_holder who) sb->s_writers.frozen = SB_UNFROZEN; sb_freeze_unlock(sb, SB_FREEZE_PAGEFAULT); wake_up(&sb->s_writers.wait_unfrozen); + wake_up_var(&sb->s_writers.frozen); deactivate_locked_super(sb); return ret; } @@ -1752,6 +1771,7 @@ int freeze_super(struct super_block *sb, enum freeze_holder who) sb->s_writers.frozen = SB_UNFROZEN; sb_freeze_unlock(sb, SB_FREEZE_FS); wake_up(&sb->s_writers.wait_unfrozen); + wake_up_var(&sb->s_writers.frozen); deactivate_locked_super(sb); return ret; } @@ -1762,6 +1782,7 @@ int freeze_super(struct super_block *sb, enum freeze_holder who) */ sb->s_writers.freeze_holders |= who; sb->s_writers.frozen = SB_FREEZE_COMPLETE; + wake_up_var(&sb->s_writers.frozen); lockdep_sb_freeze_release(sb); up_write(&sb->s_umount); return 0; @@ -1810,6 +1831,7 @@ static int thaw_super_locked(struct super_block *sb, enum freeze_holder who) if (sb_rdonly(sb)) { sb->s_writers.freeze_holders &= ~who; sb->s_writers.frozen = SB_UNFROZEN; + wake_up_var(&sb->s_writers.frozen); goto out; } @@ -1828,6 +1850,7 @@ static int thaw_super_locked(struct super_block *sb, enum freeze_holder who) sb->s_writers.freeze_holders &= ~who; sb->s_writers.frozen = SB_UNFROZEN; + wake_up_var(&sb->s_writers.frozen); sb_freeze_unlock(sb, SB_FREEZE_FS); out: wake_up(&sb->s_writers.wait_unfrozen); From patchwork Mon Jun 12 03:15:34 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Darrick J. Wong" X-Patchwork-Id: 13275420 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 64CD0C7EE2E for ; Mon, 12 Jun 2023 03:16:27 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234701AbjFLDQZ (ORCPT ); Sun, 11 Jun 2023 23:16:25 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50274 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234573AbjFLDQH (ORCPT ); Sun, 11 Jun 2023 23:16:07 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8D5FCE70; Sun, 11 Jun 2023 20:15:35 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 2385D61DD5; Mon, 12 Jun 2023 03:15:35 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 807EFC4339B; Mon, 12 Jun 2023 03:15:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1686539734; bh=GWJnpjZ+WsNh1hRt1sMJTLMEf6f06/tTxFAhmy2gjD4=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=dKOL/32dWdYnS+eSe0n9NT19jtKu72KjDDmudUh8eMenO2Mg8IfKYrFJ8XMs9UwMs ANSLFMHdLdBgkHGMC8kgScfSF6jeFUhYxtBFn2c1dJqP6hIP+zyuZCtV0pxN7fSBLv op+MIJbdtIr5JiZmmJTKCFGir0m1/1ya50cP017aHyngfeC249DFb27XFtXqHw2QBE XFTzKtkCEqjyi1hV3Hoy5QdH3VXJjdficNQgN68uepmr5+MMNCpp5EgjUKfN+5iPRI a9rH04FfTHabFIuOSk+GKaWNcySmBTp1vHFfTkgLjmwqLdbzsIhBHXZXaBd5GQK9LL Q37Su031uaQ4Q== Subject: [PATCH 3/3] fs: Drop wait_unfrozen wait queue From: "Darrick J. Wong" To: djwong@kernel.org Cc: Jan Kara , linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org, mcgrof@kernel.org, jack@suse.cz, hch@infradead.org, ruansy.fnst@fujitsu.com Date: Sun, 11 Jun 2023 20:15:34 -0700 Message-ID: <168653973399.755178.13985159536040832418.stgit@frogsfrogsfrogs> In-Reply-To: <168653971691.755178.4003354804404850534.stgit@frogsfrogsfrogs> References: <168653971691.755178.4003354804404850534.stgit@frogsfrogsfrogs> User-Agent: StGit/0.19 MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org From: Jan Kara wait_unfrozen waitqueue is used only in quota code to wait for filesystem to become unfrozen. In that place we can just use sb_start_write() - sb_end_write() pair to achieve the same. So just remove the waitqueue. Signed-off-by: Jan Kara Reviewed-by: Darrick J. Wong Signed-off-by: Darrick J. Wong --- fs/quota/quota.c | 5 +++-- fs/super.c | 4 ---- include/linux/fs.h | 1 - 3 files changed, 3 insertions(+), 7 deletions(-) diff --git a/fs/quota/quota.c b/fs/quota/quota.c index 052f143e2e0e..0e41fb84060f 100644 --- a/fs/quota/quota.c +++ b/fs/quota/quota.c @@ -895,8 +895,9 @@ static struct super_block *quotactl_block(const char __user *special, int cmd) up_write(&sb->s_umount); else up_read(&sb->s_umount); - wait_event(sb->s_writers.wait_unfrozen, - sb->s_writers.frozen == SB_UNFROZEN); + /* Wait for sb to unfreeze */ + sb_start_write(sb); + sb_end_write(sb); put_super(sb); goto retry; } diff --git a/fs/super.c b/fs/super.c index 151e0eeff2c2..fd04dda6c5c0 100644 --- a/fs/super.c +++ b/fs/super.c @@ -236,7 +236,6 @@ static struct super_block *alloc_super(struct file_system_type *type, int flags, &type->s_writers_key[i])) goto fail; } - init_waitqueue_head(&s->s_writers.wait_unfrozen); s->s_bdi = &noop_backing_dev_info; s->s_flags = flags; if (s->s_user_ns != &init_user_ns) @@ -1753,7 +1752,6 @@ int freeze_super(struct super_block *sb, enum freeze_holder who) if (ret) { sb->s_writers.frozen = SB_UNFROZEN; sb_freeze_unlock(sb, SB_FREEZE_PAGEFAULT); - wake_up(&sb->s_writers.wait_unfrozen); wake_up_var(&sb->s_writers.frozen); deactivate_locked_super(sb); return ret; @@ -1770,7 +1768,6 @@ int freeze_super(struct super_block *sb, enum freeze_holder who) "VFS:Filesystem freeze failed\n"); sb->s_writers.frozen = SB_UNFROZEN; sb_freeze_unlock(sb, SB_FREEZE_FS); - wake_up(&sb->s_writers.wait_unfrozen); wake_up_var(&sb->s_writers.frozen); deactivate_locked_super(sb); return ret; @@ -1853,7 +1850,6 @@ static int thaw_super_locked(struct super_block *sb, enum freeze_holder who) wake_up_var(&sb->s_writers.frozen); sb_freeze_unlock(sb, SB_FREEZE_FS); out: - wake_up(&sb->s_writers.wait_unfrozen); deactivate_locked_super(sb); return 0; } diff --git a/include/linux/fs.h b/include/linux/fs.h index c58a560569b3..5870fbbecb81 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1147,7 +1147,6 @@ enum { struct sb_writers { unsigned short frozen; /* Is sb frozen? */ unsigned short freeze_holders; /* Who froze fs? */ - wait_queue_head_t wait_unfrozen; /* wait for thaw */ struct percpu_rw_semaphore rw_sem[SB_FREEZE_LEVELS]; };