From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from m16.mail.126.com (m16.mail.126.com [117.135.210.8]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C09D72EEE84; Thu, 3 Sep 2026 02:25:00 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=117.135.210.8 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788402306; cv=none; b=Q8odq94hUxaLI66ZeP3CROpfDw5L18Qj7EvrbaL/CDGLakoXYdIVAl9D11dQxE6I0LSyK3O/OrZCfoMPsEk6EK5PMIpFlXf2dFcum1N7NYWEfHHVVCHzYllupqsewIFUJHC8GoVhlBswniD4dv9M/Rr/42HyJxUAesRhqaDK4Fo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1788402306; c=relaxed/simple; bh=orE0wMKRPcRDEqhAW65slXxrkNG5MR+Z2iVAwYqD1kM=; h=Message-ID:Date:From:MIME-Version:To:CC:Subject:References: In-Reply-To:Content-Type; b=O6hVrxYw3eZEVIi7HBmTpJlMwst1k0aJOJ2QUsn91EMLaw7LANt5qkWCFWislKV21RjC8KRwOrHUNUAY/WznggU6pdI9jdAtsfxf2JeF5Hp+Q7elY87ZAzt0d0LDWUdeUs+6lDxVPtK+AiP6FzTeDeZtDvp9IifEKG+aFqprrPE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=126.com; spf=pass smtp.mailfrom=126.com; dkim=pass (1024-bit key) header.d=126.com header.i=@126.com header.b=bSObvlIX; arc=none smtp.client-ip=117.135.210.8 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=126.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=126.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=126.com header.i=@126.com header.b="bSObvlIX" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=126.com; s=s110527; h=Message-ID:Date:From:MIME-Version:To:Subject: Content-Type; bh=54IXZroYKkcxKQKMPsI/ne/eA/BH5mAcEDtq0IKVRAE=; b=bSObvlIXYTiYTJWqn+OGIdfRn8FuRe9PqrU4HIPhYDOZjkpDkKtWDQgWcv6UxL hbCJO1JHvom1Kz4SsQEOrmoQ/fq2/fTvBEVCNL0wPAKWnAruqCKxeAJZbw9aXKFA iXsPgaTEBTttpz68/8lHClex7BYbAXoPqsSr5JaYVgxLc= Received: from localhost.localdomain (unknown []) by gzsmtp4 (Coremail) with SMTP id PykvCgD331622ZhqT6sGGw--.16149S2; Thu, 03 Sep 2026 10:21:42 +0800 (CST) Message-ID: <6A98D99B.5020504@126.com> Date: Thu, 03 Sep 2026 10:21:15 +0800 From: Hongling Zeng User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.2.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 To: Hongling Zeng , linkinjeon@kernel.org, hyc.lee@gmail.com CC: ntfs@lists.linux.dev, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH 1/3] ntfs: fix volume flag update races References: <20260903021930.201169-1-zenghongling@kylinos.cn> In-Reply-To: <20260903021930.201169-1-zenghongling@kylinos.cn> Content-Type: text/plain; charset=gbk; format=flowed Content-Transfer-Encoding: 8bit X-CM-TRANSID:PykvCgD331622ZhqT6sGGw--.16149S2 X-Coremail-Antispam: 1Uf129KBjvJXoW3GFWUCryrGFW5ur1xtr1kKrg_yoW3WFyfpr sayF9xKa1qyr17Wws7K3yIga1S9348Gr48Cry7Jw1av3sxtryUXF18K3WrAFnYyr97Ar1x XFWjyrW5uw1UZF7anT9S1TB71UUUUU7qnTZGkaVYY2UrUUUUjbIjqfuFe4nvWSU5nxnvy2 9KBjDUYxBIdaVFxhVjvjDU0xZFpf9x07jI0PfUUUUU= X-CM-SenderInfo: x2kr0wpolqwiqxrzqiyswou0bp/xtbBrhZkNWqY2bYjCgAA3d Hi, Sorry for the many versions of this patch. The ntfs_sync_fs() race you pointed out is fixed in patch 1/3: NVolErrors() is checked and VOLUME_IS_DIRTY is cleared inside the same mrec_lock critical section, so every interleaving with a concurrent error path leaves the volume dirty on disk. Patches 2/3 and 3/3 close the writer-side window: the runtime error paths now record NVolErrors() before taking the mrec_lock to persist VOLUME_IS_DIRTY, so a clear path running afterwards sees the flag under the lock and leaves the dirty bit alone. Looking forward to your review and feedback. Thanks, Hongling 在 2026年09月03日 10:19, Hongling Zeng 写道: > ntfs_set_volume_flags() and ntfs_clear_volume_flags() both read > vol->vol_flags outside any lock to compute the new value before handing > it to ntfs_write_volume_flags(), which only takes ni->mrec_lock around > the actual write. The read-modify-write is therefore not atomic, and two > concurrent callers can lose an update: ntfs_sync_fs() may derive a > "clean" value from vol->vol_flags while a writer concurrently records an > error and sets VOLUME_IS_DIRTY; the locked write then silently > overwrites the freshly-set dirty bit. The on-disk volume looks clean > despite the recorded errors, so chkdsk will not run on the next mount > and corrupted metadata can persist. > > Fix by moving the read-modify-write inside the mrec_lock: pass the bits > to set and to clear separately, and combine them with the current flag > state under the lock inside ntfs_write_volume_flags(). The set/clear > helpers pass only the bits to modify, not the complete flag state. The > bit manipulation is done on CPU-endian values, and the result is > converted back to little-endian before storing it. The wrappers keep > their signatures so callers are unchanged. > > Cc: stable@vger.kernel.org > Signed-off-by: Hongling Zeng > --- > - Also fix the ntfs_sync_fs() race by checking NVolErrors() and clearing > VOLUME_IS_DIRTY under ni->mrec_lock. > - Keep ntfs_set_volume_flags() and ntfs_clear_volume_flags() semantics > unchanged. > - Do not tie setting VOLUME_IS_DIRTY to NVolSetErrors() in the generic > set helper. > --- > fs/ntfs/super.c | 62 +++++++++++++++++++++++++++++++++++-------------- > 1 file changed, 45 insertions(+), 17 deletions(-) > > diff --git a/fs/ntfs/super.c b/fs/ntfs/super.c > index a1813093222b..a7977b95b967 100644 > --- a/fs/ntfs/super.c > +++ b/fs/ntfs/super.c > @@ -353,31 +353,45 @@ void ntfs_handle_error(struct super_block *sb) > } > > /* > - * ntfs_write_volume_flags - write new flags to the volume information flags > + * ntfs_write_volume_flags - apply flag changes to the volume information flags > * @vol: ntfs volume on which to modify the flags > - * @flags: new flags value for the volume information flags > + * @set_bits: bits to set in the volume information flags > + * @clear_bits: bits to clear in the volume information flags > * > * Internal function. You probably want to use ntfs_{set,clear}_volume_flags() > * instead (see below). > * > - * Replace the volume information flags on the volume @vol with the value > - * supplied in @flags. Note, this overwrites the volume information flags, so > - * make sure to combine the flags you want to modify with the old flags and use > - * the result when calling ntfs_write_volume_flags(). > + * Combine @set_bits and @clear_bits with the current in-memory flag state and > + * write the result back. The set/clear helpers pass only the bits to modify, > + * not the complete flag state. The read-modify-write happens under > + * ni->mrec_lock so that concurrent set/clear operations cannot lose updates. > + * All bit manipulation is done on CPU-endian values, and the result is > + * converted back to little-endian before storing it. > * > * Return 0 on success and -errno on error. > */ > -static int ntfs_write_volume_flags(struct ntfs_volume *vol, const __le16 flags) > +static int ntfs_write_volume_flags(struct ntfs_volume *vol, > + const __le16 set_bits, const __le16 clear_bits, > + const bool skip_if_errors) > { > struct ntfs_inode *ni = NTFS_I(vol->vol_ino); > struct volume_information *vi; > struct ntfs_attr_search_ctx *ctx; > + u16 flags; > int err; > > - ntfs_debug("Entering, old flags = 0x%x, new flags = 0x%x.", > - le16_to_cpu(vol->vol_flags), le16_to_cpu(flags)); > mutex_lock(&ni->mrec_lock); > - if (vol->vol_flags == flags) > + > + if (skip_if_errors && NVolErrors(vol)) > + goto done; > + > + flags = le16_to_cpu(vol->vol_flags); > + flags |= le16_to_cpu(set_bits) & le16_to_cpu(VOLUME_FLAGS_MASK); > + flags &= ~(le16_to_cpu(clear_bits) & le16_to_cpu(VOLUME_FLAGS_MASK)); > + ntfs_debug("Entering, old flags = 0x%x, new flags = 0x%x.", > + le16_to_cpu(vol->vol_flags), flags); > + > + if (le16_to_cpu(vol->vol_flags) == flags) > goto done; > > ctx = ntfs_attr_get_search_ctx(ni, NULL); > @@ -393,7 +407,7 @@ static int ntfs_write_volume_flags(struct ntfs_volume *vol, const __le16 flags) > > vi = (struct volume_information *)((u8 *)ctx->attr + > le16_to_cpu(ctx->attr->data.resident.value_offset)); > - vol->vol_flags = vi->flags = flags; > + vol->vol_flags = vi->flags = cpu_to_le16(flags); > mark_mft_record_dirty(ctx->ntfs_ino); > ntfs_attr_put_search_ctx(ctx); > done: > @@ -414,13 +428,14 @@ static int ntfs_write_volume_flags(struct ntfs_volume *vol, const __le16 flags) > * @flags: flags to set on the volume > * > * Set the bits in @flags in the volume information flags on the volume @vol. > + * The bits are combined with the current flag state under the lock in > + * ntfs_write_volume_flags(), so concurrent updates are not lost. > * > * Return 0 on success and -errno on error. > */ > int ntfs_set_volume_flags(struct ntfs_volume *vol, __le16 flags) > { > - flags &= VOLUME_FLAGS_MASK; > - return ntfs_write_volume_flags(vol, vol->vol_flags | flags); > + return ntfs_write_volume_flags(vol, flags, 0, false); > } > > /* > @@ -429,14 +444,27 @@ int ntfs_set_volume_flags(struct ntfs_volume *vol, __le16 flags) > * @flags: flags to clear on the volume > * > * Clear the bits in @flags in the volume information flags on the volume @vol. > + * The bits are combined with the current flag state under the lock in > + * ntfs_write_volume_flags(), so concurrent updates are not lost. > * > * Return 0 on success and -errno on error. > */ > int ntfs_clear_volume_flags(struct ntfs_volume *vol, __le16 flags) > { > - flags &= VOLUME_FLAGS_MASK; > - flags = vol->vol_flags & cpu_to_le16(~le16_to_cpu(flags)); > - return ntfs_write_volume_flags(vol, flags); > + return ntfs_write_volume_flags(vol, 0, flags, false); > +} > + > +/* > + * ntfs_clear_volume_dirty_if_no_errors - clear dirty bit if no errors exist > + * @vol: ntfs volume whose dirty bit should be cleared > + * > + * Check NVolErrors() and clear VOLUME_IS_DIRTY under the same mrec_lock so > + * ntfs_sync_fs() cannot clear the dirty bit after a concurrent error has been > + * recorded. > + */ > +static int ntfs_clear_volume_dirty_if_no_errors(struct ntfs_volume *vol) > +{ > + return ntfs_write_volume_flags(vol, 0, VOLUME_IS_DIRTY, true); > } > > int ntfs_write_volume_label(struct ntfs_volume *vol, char *label) > @@ -1862,7 +1890,7 @@ static int ntfs_sync_fs(struct super_block *sb, int wait) > return 0; > > /* If there are some dirty buffers in the bdev inode */ > - if (ntfs_clear_volume_flags(vol, VOLUME_IS_DIRTY)) { > + if (ntfs_clear_volume_dirty_if_no_errors(vol)) { > ntfs_warning(sb, "Failed to clear dirty bit in volume information flags. Run chkdsk."); > err = -EIO; > }