From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794249406; b=i/Hya1KQmrqrRWbsmE/KFPRxBecYVOe5iukMINp4wy2o2s45oMBEbVCWmN6/tGLbWVAD lEFZbWhMWN7Xt3taYvYqBA6HgDizqUwPskoJ32lI4Ag3WUHamlPy900EVo7dpPD3ljMMk JLyKBDXnRi3dua6Cmd/AUnAOc4KAKagK6gJ5JiSuyoFyk1fd26nFYi9/pQkjR2rjg8+Tn b/YT9GSRsnsuCV4vmFEaUq/Jgd5bIrJ7Lmk44y6OFksSoqDQ2LqsAKPi/ldQFNmbMJ0BJ V7Jc6HFvg+sAAbOnzAh2glvgWnVxFPOOGXGEyzK+bg3FfORUgYQN1iVxPgrCSA+0wwQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794249406; h=Received:DKIM-Signature:Message-ID:From:Subject:Reply-To:To:Cc: In-Reply-To:References:Content-Type:Content-Transfer-Encoding:Date; bh=+FugmqOuHfMm55/hhVDOspEg6KmglH5dPW/iir3zkXQ=; b=U4KnTVKzGLXrWNODGeD9bZSLjyjj63Eslw0tEkPHa2eIOmsTlZFN7yawZaDCKmWGRYCP +mw0hklYDP5hJmp0GuYn7csPb6J4Zxx6xdTW5J9IRvv2o2oQRrNCv23D0hSTkzhAXtWAb Stc8ZGiCeZlNaMpujVcY2jWuqu7iiZ+fRcM2nxvzuvkUUqd1GpPCWU3T05uKEt/qwEoy1 /1Wfmd408gPRurEemvNmt+96ZCTgQdGxVw420WkEoJPgiNuA5VoWTe2O8xFurHq7kVK/o EYzF9cZ1blg/M/KJyqQjQGvu8K/hYdGRwtBFICyjeJu8IT//7rSdyMgSDuMLwDtWn1w== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=QD9RQ6qD; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3FB06606A31C for ; Mon, 9 Nov 2026 18:36:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=QD9RQ6qD Received: by smtp.kernel.org (Postfix) with ESMTPSA id 993C91F0089F; Mon, 9 Nov 2026 18:36:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794249405; bh=+FugmqOuHfMm55/hhVDOspEg6KmglH5dPW/iir3zkXQ=; h=From:Subject:Reply-To:To:Cc:In-Reply-To:References:Date; b=QD9RQ6qDUjTiL06DJsJq2plBIrcenytMx0zGBjl7Rcx5EI8yes3YGL2s0DHFGTDgZ p4ok0LyFMIvihfhtinBOyOlJr7hbkBsTsSM9osZP6YWT4ydWQcNFh29epB+AFM2mQs pvdbZyximlZ99DL2Vib1JUfXjuiDFMxenh5kU5TE1dn2eJwtgjgN/CVwtkMDk0TIlS UNXTDea3PmFq1qG9Tz8HweKPD0xxFOtcUm2gkXSpP2BOV8vUDLI9A94sGKTinjtpjU ZSoAB9oHzmajulL42EfIXjtgbyPA9/LSyprUT0/16Wut/tQmlevmPO5e6o6ngBnlZo ULZzlBfPZYGGg== Message-ID: From: sashiko-bot@kernel.org Subject: Re: [PATCH RFC v3 10/14] ext2: drop mmb_sync() from ext2_evict_inode() Reply-To: sashiko-reviews@lists.linux.dev To: "Christian Brauner" Cc: linux-ext4@vger.kernel.org, tytso@mit.edu In-Reply-To: <20261109-work-inode-metadata_writeback-v3-10-91ac6c024018@kernel.org> References: <20261109-work-inode-metadata_writeback-v3-0-91ac6c024018@kernel.org> <20261109-work-inode-metadata_writeback-v3-10-91ac6c024018@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Date: Mon, 09 Nov 2026 18:36:45 +0000 X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list Thank you for your contribution! Sashiko AI review found 1 potential issue to consider: - [Medium] ext2: unsynced metadata buffers in ext2_evict_inode() on mmb_sync() race -- commit 87b835e8b247e4798e3fb46ec519ae23df154b20 Author: Christian Brauner ext2: drop mmb_sync() from ext2_evict_inode() This commit removes the mmb_sync() call from ext2_evict_inode(), relying on evict() to write out metadata buffers tracked via I_METADATA_WRITEBACK. > diff --git a/fs/ext2/inode.c b/fs/ext2/inode.c > index 9261b666d043a..4c38a3a8ea4d7 100644 > --- a/fs/ext2/inode.c > +++ b/fs/ext2/inode.c > @@ -91,8 +91,6 @@ void ext2_evict_inode(struct inode * inode) > if (inode->i_blocks) > ext2_truncate_blocks(inode, 0); > ext2_xattr_delete_inode(inode); > - } else { > - mmb_sync(&EXT2_I(inode)->i_metadata_bhs); > } > mmb_invalidate(&EXT2_I(inode)->i_metadata_bhs); > clear_inode(inode); [Severity: Medium] Can ext2_evict_inode() invalidate dirty metadata buffers on i_metadata_bhs without writing them out if mmb_mark_buffer_dirty() races with mmb_sync()? In __ext2_truncate_blocks(), ext2_free_branches() modifies partial->bh->b_data and calls mark_inode_dirty(inode) before calling mmb_mark_buffer_dirty(). If a concurrent writeback clears I_DIRTY and I_METADATA_WRITEBACK in __writeback_single_inode() and enters mmb_sync(), mmb_sync() temporarily sets bh->b_mmb to NULL in __remove_assoc_queue() and restores bh->b_mmb =3D mmb if the buffer was dirtied again: CPU0 CPU1 __ext2_truncate_blocks() ext2_free_branches() mark_inode_dirty(inode) __writeback_single_inode() inode_state_clear(..., I_METADATA_WRITEBACK) ext2_sync_inode_metadata() mmb_sync() spin_lock(&mmb->lock) __remove_assoc_queue() bh->b_mmb =3D NULL mmb_mark_buffer_dirty() mark_buffer_dirty(bh) if (!bh->b_mmb) // true if (buffer_dirty(bh)) { list_add(..., &mmb->list) bh->b_mmb =3D mmb } spin_unlock(&mmb->lock) spin_lock(&mmb->lock) if (cmpxchg(&bh->b_mmb, NULL, mmb) !=3D NULL) { spin_unlock(&mmb->lock) return; <-- skips setting I_METADATA_WRITEBACK } Because mmb_sync() only waits on in-flight I/O in its second loop without submitting new I/O for the re-dirtied buffer, and mmb_mark_buffer_dirty() returns early without setting I_METADATA_WRITEBACK, the dirty buffer remains on i_metadata_bhs with I_METADATA_WRITEBACK clear on the inode. With mmb_sync() removed from ext2_evict_inode(), evict() skips sync_inode_metadata() and ext2_evict_inode() detaches the dirty buffer via mmb_invalidate(). If the inode is later re-read from disk and fsync()ed before background block device writeback flushes the buffer, fsync() will no longer see the buffer on i_metadata_bhs and can return before the indirect block is persisted to disk. --=20 Sashiko AI review =C2=B7 https://sashiko.dev/#/patchset/20261109-work-inode= -metadata_writeback-v3-0-91ac6c024018@kernel.org?part=3D10