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Fri, 31 May 2024 16:15:36 +0000 (UTC) Received: from redhat.com (unknown [10.39.193.235]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 28B8A40C6EB7; Fri, 31 May 2024 16:15:36 +0000 (UTC) Date: Fri, 31 May 2024 18:15:35 +0200 From: Kevin Wolf To: Amjad Alsharafi Cc: qemu-devel@nongnu.org, Hanna Reitz , "open list:vvfat" Subject: Re: [PATCH v3 1/6] vvfat: Fix bug in writing to middle of file Message-ID: References: <2871281d8ea41fb4d7ef8f9beeaba017a1717019.1716717181.git.amjadsharafi10@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2871281d8ea41fb4d7ef8f9beeaba017a1717019.1716717181.git.amjadsharafi10@gmail.com> X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.2 Received-SPF: pass client-ip=170.10.129.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.085, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Am 26.05.2024 um 11:56 hat Amjad Alsharafi geschrieben: > Before this commit, the behavior when calling `commit_one_file` for > example with `offset=0x2000` (second cluster), what will happen is that > we won't fetch the next cluster from the fat, and instead use the first > cluster for the read operation. > > This is due to off-by-one error here, where `i=0x2000 !< offset=0x2000`, > thus not fetching the next cluster. > > Signed-off-by: Amjad Alsharafi Reviewed-by: Kevin Wolf Tested-by: Kevin Wolf > diff --git a/block/vvfat.c b/block/vvfat.c > index 9d050ba3ae..ab342f0743 100644 > --- a/block/vvfat.c > +++ b/block/vvfat.c > @@ -2525,7 +2525,7 @@ commit_one_file(BDRVVVFATState* s, int dir_index, uint32_t offset) > return -1; > } > > - for (i = s->cluster_size; i < offset; i += s->cluster_size) > + for (i = s->cluster_size; i <= offset; i += s->cluster_size) > c = modified_fat_get(s, c); While your change results in the correct behaviour, I think I would prefer the code to be changed like this so that at the start of each loop iteration, 'i' always refers to the offset that matches 'c': for (i = 0; i < offset; i += s->cluster_size) { c = modified_fat_get(s, c); } I'm also adding braces here to make the code conform with the QEMU coding style. You can use scripts/checkpatch.pl to make sure that all code you add has the correct style. Much of the vvfat code predates the coding style, so you'll often have to change style when you touch a line. (Which is good, because it slowly fixes the existing mess.) You can keep my Reviewed/Tested-by if you change this. Kevin