[{"id":3676718,"web_url":"http://patchwork.ozlabs.org/comment/3676718/","msgid":"<20260413124703.GA20496@macsyma-wired.lan>","list_archive_url":null,"date":"2026-04-13T12:47:03","subject":"Re: [RFC v2 0/1] ext4: fail fast on repeated buffer_head reads after\n IO failure","submitter":{"id":350,"url":"http://patchwork.ozlabs.org/api/people/350/","name":"Theodore Tso","email":"tytso@mit.edu"},"content":"On Mon, Apr 13, 2026 at 02:24:59PM +0800, Diangang Li wrote:\n> From: Diangang Li \n> \n> A production system reported hung tasks blocked for 300s+ in ext4\n> buffer_head paths....\n> \n> [Tue Mar 24 14:16:24 2026] blk_update_request: I/O error, dev sdi,\n> sector 10704150288 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0\n> [Tue Mar 24 14:16:25 2026] blk_update_request: I/O error, dev sdi,\n> sector 10704488160 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0\n> [Tue Mar 24 14:16:26 2026] blk_update_request: I/O error, dev sdi,\n> sector 10704382912 op 0x0:(READ) flags 0x0 phys_seg 1 prio class 0\n\nI wonder whether the ext4 layer is the right place to be handle this\nsort of issue. For example, it could be handled by having a subsystem\nscanning dmesg (or by wiring up notifications so block device errors\nget sent to a userspace daemon), and when certain criteria is met, the\nmachine is automatically sent to hardware operations to run\ndiagnostics and (most likey) replace the failing disk.\n\nIt could also be handled in the driver or SCSI layer so the \"fail\nfast\" semantics are handled there, so that it supports all file\nsystems, not just ext4. The SCSI layer also has more information\nabout the type of error; you might want to handle things like media\nerrors differently from Fibre Channel or iSCSI timeouts (which might\nbe something where \"fast fast\" is not appropriate).\n\nBy the time the error gets propagated up to the buffer head, we lose a\nlot of detail about why the error took place. Also, in the long term\nwe will hopefully be moving away from using buffer cache.\n\n \t\t \t \t \t - Ted","headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linux-ext4@vger.kernel.org"],"Delivered-To":["patchwork-incoming@legolas.ozlabs.org","patchwork-incoming@ozlabs.org"],"Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=mit.edu header.i=@mit.edu header.a=rsa-sha256\n header.s=outgoing header.b=Dr7NHjXJ;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=ozlabs.org\n (client-ip=150.107.74.76; helo=mail.ozlabs.org;\n envelope-from=srs0=snoq=cm=vger.kernel.org=linux-ext4+bounces-15809-patchwork-incoming=ozlabs.org@ozlabs.org;\n receiver=patchwork.ozlabs.org)","gandalf.ozlabs.org;\n arc=pass smtp.remote-ip=\"2600:3c0a:e001:db::12fc:5321\"\n arc.chain=subspace.kernel.org","gandalf.ozlabs.org;\n dmarc=pass (p=none dis=none) header.from=mit.edu","gandalf.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=mit.edu header.i=@mit.edu header.a=rsa-sha256\n header.s=outgoing header.b=Dr7NHjXJ;\n\tdkim-atps=neutral","gandalf.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org\n (client-ip=2600:3c0a:e001:db::12fc:5321; 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arc=none smtp.client-ip=18.9.28.11"],"DKIM-Signature":"v=1; a=rsa-sha256; c=relaxed/relaxed; d=mit.edu; s=outgoing;\n\tt=1776084487; bh=ew0N4RW/+mMo1okUz8IGgXrBvzrPN7l+s8J2ydS6XZI=;\n\th=Date:From:Subject:Message-ID:MIME-Version:Content-Type;\n\tb=Dr7NHjXJPY+Ug6d5M4eVJih7sF68tlFdq1cMBnCxIwJJkQob4ee6dd0dXgT5zcXOs\n\t Aq4t9D3pjx4bp/bw7i3vf9AJdc2XGYB7eyq+0PKUaLa6ZurQunYb9bJLVHsJVoobxF\n\t bOwGP6sk/x8lXvfQib94symCoyaKSJTSYQlki3v0bsLZr7HjZ9gP3rbY3B17qvwo7K\n\t E6pChC1Yjfh1spZwnVOqZ4+o4sxXzEWLrHUvFzsqlknMx03hiSGq+Eh2SAeIuxlwkQ\n\t nZ2numKdP/Y+6lmfv89AUJY8cqA5FZLODZlW60zdD0KdNdRTwEd6TD43h3WJ4xbT+/\n\t 6c/5wrg0ukgPQ==","Date":"Mon, 13 Apr 2026 08:47:03 -0400","From":"\"Theodore Tso\" ","To":"Diangang Li ","Cc":"adilger.kernel@dilger.ca, linux-ext4@vger.kernel.org,\n linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,\n changfengnan@bytedance.com, yizhang089@gmail.com, willy@infradead.org,\n Diangang Li ","Subject":"Re: [RFC v2 0/1] ext4: fail fast on repeated buffer_head reads after\n IO failure","Message-ID":"<20260413124703.GA20496@macsyma-wired.lan>","References":"<20260325093349.630193-1-diangangli@gmail.com>\n <20260413062500.1380307-1-diangangli@gmail.com>","Precedence":"bulk","X-Mailing-List":"linux-ext4@vger.kernel.org","List-Id":"","List-Subscribe":"","List-Unsubscribe":"","MIME-Version":"1.0","Content-Type":"text/plain; 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