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Thu, 14 Mar 2019 01:40:24 +0000 Received: from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75]) by aserv0022.oracle.com (8.14.4/8.14.4) with ESMTP id x2E1eM92016312 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 14 Mar 2019 01:40:23 GMT Received: from abhmp0022.oracle.com (abhmp0022.oracle.com [141.146.116.28]) by userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id x2E1eLVq028135; Thu, 14 Mar 2019 01:40:22 GMT Received: from [172.20.10.2] (/183.90.36.70) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Wed, 13 Mar 2019 18:40:21 -0700 Subject: Re: [PATCH 2/2] btrfs: fix vanished compression property after failed set To: dsterba@suse.cz, linux-btrfs@vger.kernel.org References: <1552455379-2311-1-git-send-email-anand.jain@oracle.com> <1552455379-2311-2-git-send-email-anand.jain@oracle.com> <60c3e0c1-52dd-5389-e244-c82776b214a1@oracle.com> <20190313174539.GG31119@twin.jikos.cz> From: Anand Jain Message-ID: <501289dd-ab15-d10c-bcce-8efcaf939b79@oracle.com> Date: Thu, 14 Mar 2019 09:40:32 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.5.0 MIME-Version: 1.0 In-Reply-To: <20190313174539.GG31119@twin.jikos.cz> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Proofpoint-Virus-Version: vendor=nai engine=5900 definitions=9194 signatures=668685 X-Proofpoint-Spam-Details: rule=notspam policy=default score=0 priorityscore=1501 malwarescore=0 suspectscore=0 phishscore=0 bulkscore=0 spamscore=0 clxscore=1015 lowpriorityscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1810050000 definitions=main-1903140008 Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On 3/14/19 1:45 AM, David Sterba wrote: > On Wed, Mar 13, 2019 at 06:33:50PM +0800, Anand Jain wrote: >> >> >> >> On 3/13/19 1:36 PM, Anand Jain wrote: >>> The compression property resets to NULL, instead of the old value if we >>> fail to set the new compression parameter. >>> >>> btrfs prop get /btrfs compression >>> compression=lzo >>> btrfs prop set /btrfs compression zli >>> ERROR: failed to set compression for /btrfs: Invalid argument >>> btrfs prop get /btrfs compression >>> >>> This is because the compression property ->validate() is successful for >>> 'zli' as the strncmp() used the len passed from the userland. >>> >>> Fix it by using the expected string length in strncmp(). >>> >>> Signed-off-by: Anand Jain >>> --- >>> fs/btrfs/props.c | 6 +++--- >>> 1 file changed, 3 insertions(+), 3 deletions(-) >>> >>> diff --git a/fs/btrfs/props.c b/fs/btrfs/props.c >>> index ef6502a94712..7aa362c2fbcf 100644 >>> --- a/fs/btrfs/props.c >>> +++ b/fs/btrfs/props.c >>> @@ -277,11 +277,11 @@ static int prop_compression_validate(struct inode *inode, const char *value, >>> if (!value) >>> return 0; >>> >>> - if (!strncmp("lzo", value, len)) >>> + if (!strncmp("lzo", value, 3)) >>> return 0; >>> - else if (!strncmp("zlib", value, len)) >>> + else if (!strncmp("zlib", value, 4)) >>> return 0; >>> - else if (!strncmp("zstd", value, len)) >>> + else if (!strncmp("zstd", value, 4)) >>> return 0; >>> >> >> >> Nack. >> Now some junk value after expected string is not an error. >> such as.. >> >> btrfs prop set /btrfs compression lzo110 > > This was intentional when the zlib levels were introduced so older > kernels can understand newer compression specifier but still have a sane > fallback (ie use the default level). Now it would be better to extend > the validation to parse the method:level format at least. But as > mentioned in the other mail, the level needs to be propagated elsewhere > too so it's not just a change to the validation. > Compression levels properties can be implemented in a newer set of the patches? So I believe this set ok to merge. The other way to fix this was to save and rewrite the old parameter, but that's not a good idea as well, because when parameter is not valid we should rather fail without any update (generation/transid should also remain unchanged, there is a bug [1] in the original code which shall be fixed separately). [1] with this patch, btrfs in dump-super /dev/sdb | grep "^generation"; btrfs prop set /btrfs compression zli; sync; btrfs in dump-super /dev/sdb | grep "^generation" generation 21 ERROR: failed to set compression for /btrfs: Invalid argument generation 22 Thanks, Anand