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Mon, 23 Sep 2024 09:43:03 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id pZ9mByc48WZWCAAAD6G6ig (envelope-from ); Mon, 23 Sep 2024 09:43:03 +0000 Message-ID: Date: Mon, 23 Sep 2024 11:43:02 +0200 Precedence: bulk X-Mailing-List: linux-raid@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC 0/6] bio_split() error handling rework To: John Garry , axboe@kernel.dk, hch@lst.de Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, martin.petersen@oracle.com References: <20240919092302.3094725-1-john.g.garry@oracle.com> <86f3586d-5b0a-483e-b94b-d4515d5c5244@oracle.com> Content-Language: en-US From: Hannes Reinecke In-Reply-To: <86f3586d-5b0a-483e-b94b-d4515d5c5244@oracle.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Spam-Level: X-Spamd-Result: default: False [-4.30 / 50.00]; BAYES_HAM(-3.00)[100.00%]; NEURAL_HAM_LONG(-1.00)[-1.000]; NEURAL_HAM_SHORT(-0.20)[-1.000]; MIME_GOOD(-0.10)[text/plain]; RCVD_VIA_SMTP_AUTH(0.00)[]; RCPT_COUNT_SEVEN(0.00)[7]; ARC_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; MID_RHS_MATCH_FROM(0.00)[]; RCVD_TLS_ALL(0.00)[]; DKIM_SIGNED(0.00)[suse.de:s=susede2_rsa,suse.de:s=susede2_ed25519]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; FROM_EQ_ENVFROM(0.00)[]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_COUNT_TWO(0.00)[2]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:email,suse.de:mid,imap1.dmz-prg2.suse.org:helo] X-Spam-Score: -4.30 X-Spam-Flag: NO On 9/23/24 09:19, John Garry wrote: > On 23/09/2024 06:53, Hannes Reinecke wrote: >> On 9/19/24 11:22, John Garry wrote: >>> bio_split() error handling could be improved as follows: >>> - Instead of returning NULL for an error - which is vague - return a >>>    PTR_ERR, which may hint what went wrong. >>> - Remove BUG_ON() calls - which are generally not preferred - and >>> instead >>>    WARN and pass an error code back to the caller. Many callers of >>>    bio_split() don't check the return code. As such, for an error we >>> would >>>    be getting a crash still from an invalid pointer dereference. >>> >>> Most bio_split() callers don't check the return value. However, it could >>> be argued the bio_split() calls should not fail. So far I have just >>> fixed up the md RAID code to handle these errors, as that is my interest >>> now. >>> >>> Sending as an RFC as unsure if this is the right direction. >>> >>> The motivator for this series was initial md RAID atomic write >>> support in >>> https://lore.kernel.org/linux-block/21f19b4b-4b83-4ca2- >>> a93b-0a433741fd26@oracle.com/ >>> >>> There I wanted to ensure that we don't split an atomic write bio, and it >>> made more sense to handle this in bio_split() (instead of the >>> bio_split() >>> caller). >>> >>> John Garry (6): >>>    block: Rework bio_split() return value >>>    block: Error an attempt to split an atomic write in bio_split() >>>    block: Handle bio_split() errors in bio_submit_split() >>>    md/raid0: Handle bio_split() errors >>>    md/raid1: Handle bio_split() errors >>>    md/raid10: Handle bio_split() errors >>> >>>   block/bio.c                 | 14 ++++++++++---- >>>   block/blk-crypto-fallback.c |  2 +- >>>   block/blk-merge.c           |  5 +++++ >>>   drivers/md/raid0.c          | 10 ++++++++++ >>>   drivers/md/raid1.c          |  8 ++++++++ >>>   drivers/md/raid10.c         | 18 ++++++++++++++++++ >>>   6 files changed, 52 insertions(+), 5 deletions(-) >>> >> You are missing '__bio_split_to_limits()' which looks as it would need >> to be modified, too. >> > > In __bio_split_to_limits(), for REQ_OP_DISCARD, REQ_OP_SECURE_ERASE, and > REQ_OP_WRITE_ZEROES, we indirectly call bio_split(). And bio_split() > might error. But functions like bio_split_discard() can return NULL for > cases where a split is not required. So I suppose we need to check > IS_ERR(split) for those request types mentioned. For NULL being > returned, we would still have the __bio_split_to_limits() is "if > (split)" check. > Indeed. And then you'll need to modify nvme: diff --git a/drivers/nvme/host/multipath.c b/drivers/nvme/host/multipath.c index f72c5a6a2d8e..c99f51e7730e 100644 --- a/drivers/nvme/host/multipath.c +++ b/drivers/nvme/host/multipath.c @@ -453,7 +453,7 @@ static void nvme_ns_head_submit_bio(struct bio *bio) * pool from the original queue to allocate the bvecs from. */ bio = bio_split_to_limits(bio); - if (!bio) + if (IS_ERR_OR_NULL(bio)) return; srcu_idx = srcu_read_lock(&head->srcu); Cheers, Hannes -- Dr. Hannes Reinecke Kernel Storage Architect hare@suse.de +49 911 74053 688 SUSE Software Solutions GmbH, Frankenstr. 146, 90461 Nürnberg HRB 36809 (AG Nürnberg), GF: I. Totev, A. McDonald, W. Knoblich