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Mon, 18 Dec 2023 15:09:06 +0000 (UTC) Received: from dovecot-director2.suse.de ([10.150.64.162]) by imap2.dmz-prg2.suse.org with ESMTPSA id nAvyBJJggGU3dwAAn2gu4w (envelope-from ); Mon, 18 Dec 2023 15:09:06 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id 84782A07E0; Mon, 18 Dec 2023 16:09:05 +0100 (CET) Date: Mon, 18 Dec 2023 16:09:05 +0100 From: Jan Kara To: Baokun Li Cc: linux-ext4@vger.kernel.org, tytso@mit.edu, adilger.kernel@dilger.ca, jack@suse.cz, ritesh.list@gmail.com, linux-kernel@vger.kernel.org, yi.zhang@huawei.com, yangerkun@huawei.com, yukuai3@huawei.com, stable@vger.kernel.org Subject: Re: [PATCH 4/4] ext4: avoid dividing by 0 in mb_update_avg_fragment_size() when block bitmap corrupt Message-ID: <20231218150905.llu5tgjgen4nxthq@quack3> References: <20231218141814.1477338-1-libaokun1@huawei.com> <20231218141814.1477338-5-libaokun1@huawei.com> <20231218144342.2we3j2dtyedulfga@quack3> Precedence: bulk X-Mailing-List: linux-ext4@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231218144342.2we3j2dtyedulfga@quack3> X-Spam-Score: 1.80 X-Spamd-Result: default: False [1.80 / 50.00]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; BAYES_HAM(-0.10)[64.96%]; FROM_HAS_DN(0.00)[]; TO_DN_SOME(0.00)[]; FREEMAIL_ENVRCPT(0.00)[gmail.com]; TO_MATCH_ENVRCPT_ALL(0.00)[]; TAGGED_RCPT(0.00)[]; MIME_GOOD(-0.10)[text/plain]; RCVD_COUNT_THREE(0.00)[3]; DKIM_SIGNED(0.00)[suse.cz:s=susede2_rsa,suse.cz:s=susede2_ed25519]; RCPT_COUNT_SEVEN(0.00)[11]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.com:email]; FUZZY_BLOCKED(0.00)[rspamd.com]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+]; MID_RHS_NOT_FQDN(0.50)[]; FREEMAIL_CC(0.00)[vger.kernel.org,mit.edu,dilger.ca,suse.cz,gmail.com,huawei.com]; RCVD_TLS_ALL(0.00)[]; SUSPICIOUS_RECIPS(1.50)[] Authentication-Results: smtp-out2.suse.de; none X-Spam-Level: * X-Spam-Flag: NO On Mon 18-12-23 15:43:42, Jan Kara wrote: > On Mon 18-12-23 22:18:14, Baokun Li wrote: > > When bb_free is not 0 but bb_fragments is 0, return directly to avoid > > system crash due to division by zero. > > How could this possibly happen? bb_fragments is the number of free space > extents and bb_free is the number of free blocks. No free space extents => > no free blocks seems pretty obvious? You can see the logic in > ext4_mb_generate_buddy()... Oh, I see. This is probably about "bitmap corrupted case". But still both allocation and freeing of blocks shouldn't operate on bitmaps marked as corrupted so this should not happen? Honza -- Jan Kara SUSE Labs, CR