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Tue, 4 Feb 2020 16:20:32 -0600 (CST) Subject: Re: [PATCH v2 2/7] xfs: Update checking excl. locks for ilock To: Dave Chinner Cc: Christoph Hellwig , Pavel Reichl , linux-xfs@vger.kernel.org, Dave Chinner References: <20200203175850.171689-1-preichl@redhat.com> <20200203175850.171689-3-preichl@redhat.com> <20200204062118.GB2910@infradead.org> <80f1173e-9181-c8cc-c06f-cbbfaa46a138@sandeen.net> <20200204210632.GL20628@dread.disaster.area> From: Eric Sandeen Autocrypt: addr=sandeen@sandeen.net; prefer-encrypt=mutual; keydata= mQINBE6x99QBEADMR+yNFBc1Y5avoUhzI/sdR9ANwznsNpiCtZlaO4pIWvqQJCjBzp96cpCs nQZV32nqJBYnDpBDITBqTa/EF+IrHx8gKq8TaSBLHUq2ju2gJJLfBoL7V3807PQcI18YzkF+ WL05ODFQ2cemDhx5uLghHEeOxuGj+1AI+kh/FCzMedHc6k87Yu2ZuaWF+Gh1W2ix6hikRJmQ vj5BEeAx7xKkyBhzdbNIbbjV/iGi9b26B/dNcyd5w2My2gxMtxaiP7q5b6GM2rsQklHP8FtW ZiYO7jsg/qIppR1C6Zr5jK1GQlMUIclYFeBbKggJ9mSwXJH7MIftilGQ8KDvNuV5AbkronGC sEEHj2khs7GfVv4pmUUHf1MRIvV0x3WJkpmhuZaYg8AdJlyGKgp+TQ7B+wCjNTdVqMI1vDk2 BS6Rg851ay7AypbCPx2w4d8jIkQEgNjACHVDU89PNKAjScK1aTnW+HNUqg9BliCvuX5g4z2j gJBs57loTWAGe2Ve3cMy3VoQ40Wt3yKK0Eno8jfgzgb48wyycINZgnseMRhxc2c8hd51tftK LKhPj4c7uqjnBjrgOVaVBupGUmvLiePlnW56zJZ51BR5igWnILeOJ1ZIcf7KsaHyE6B1mG+X dmYtjDhjf3NAcoBWJuj8euxMB6TcQN2MrSXy5wSKaw40evooGwARAQABtCVFcmljIFIuIFNh bmRlZW4gPHNhbmRlZW5Ac2FuZGVlbi5uZXQ+iQI7BBMBAgAlAhsDBgsJCAcDAgYVCAIJCgsE FgIDAQIeAQIXgAUCUzMzbAIZAQAKCRAgrhaS4T3e4Fr7D/wO+fenqVvHjq21SCjDCrt8HdVj aJ28B1SqSU2toxyg5I160GllAxEHpLFGdbFAhQfBtnmlY9eMjwmJb0sCIrkrB6XNPSPA/B2B UPISh0z2odJv35/euJF71qIFgWzp2czJHkHWwVZaZpMWWNvsLIroXoR+uA9c2V1hQFVAJZyk EE4xzfm1+oVtjIC12B9tTCuS00pY3AUy21yzNowT6SSk7HAzmtG/PJ/uSB5wEkwldB6jVs2A sjOg1wMwVvh/JHilsQg4HSmDfObmZj1d0RWlMWcUE7csRnCE0ZWBMp/ttTn+oosioGa09HAS 9jAnauznmYg43oQ5Akd8iQRxz5I58F/+JsdKvWiyrPDfYZtFS+UIgWD7x+mHBZ53Qjazszox gjwO9ehZpwUQxBm4I0lPDAKw3HJA+GwwiubTSlq5PS3P7QoCjaV8llH1bNFZMz2o8wPANiDx 5FHgpRVgwLHakoCU1Gc+LXHXBzDXt7Cj02WYHdFzMm2hXaslRdhNGowLo1SXZFXa41KGTlNe 4di53y9CK5ynV0z+YUa+5LR6RdHrHtgywdKnjeWdqhoVpsWIeORtwWGX8evNOiKJ7j0RsHha WrePTubr5nuYTDsQqgc2r4aBIOpeSRR2brlT/UE3wGgy9LY78L4EwPR0MzzecfE1Ws60iSqw Pu3vhb7h3bkCDQROsffUARAA0DrUifTrXQzqxO8aiQOC5p9Tz25Np/Tfpv1rofOwL8VPBMvJ X4P5l1V2yd70MZRUVgjmCydEyxLJ6G2YyHO2IZTEajUY0Up+b3ErOpLpZwhvgWatjifpj6bB SKuDXeThqFdkphF5kAmgfVAIkan5SxWK3+S0V2F/oxstIViBhMhDwI6XsRlnVBoLLYcEilxA 2FlRUS7MOZGmRJkRtdGD5koVZSM6xVZQSmfEBaYQ/WJBGJQdPy94nnlAVn3lH3+N7pXvNUuC GV+t4YUt3tLcRuIpYBCOWlc7bpgeCps5Xa0dIZgJ8Louu6OBJ5vVXjPxTlkFdT0S0/uerCG5 1u8p6sGRLnUeAUGkQfIUqGUjW2rHaXgWNvzOV6i3tf9YaiXKl3avFaNW1kKBs0T5M1cnlWZU Utl6k04lz5OjoNY9J/bGyV3DSlkblXRMK87iLYQSrcV6cFz9PRl4vW1LGff3xRQHngeN5fPx ze8X5NE3hb+SSwyMSEqJxhVTXJVfQWWW0dQxP7HNwqmOWYF/6m+1gK/Y2gY3jAQnsWTru4RV TZGnKwEPmOCpSUvsTRXsVHgsWJ70qd0yOSjWuiv4b8vmD3+QFgyvCBxPMdP3xsxN5etheLMO gRwWpLn6yNFq/xtgs+ECgG+gR78yXQyA7iCs5tFs2OrMqV5juSMGmn0kxJUAEQEAAYkCHwQY AQIACQUCTrH31AIbDAAKCRAgrhaS4T3e4BKwD/0ZOOmUNOZCSOLAMjZx3mtYtjYgfUNKi0ki YPveGoRWTqbis8UitPtNrG4XxgzLOijSdOEzQwkdOIp/QnZhGNssMejCnsluK0GQd+RkFVWN mcQT78hBeGcnEMAXZKq7bkIKzvc06GFmkMbX/gAl6DiNGv0UNAX+5FYh+ucCJZSyAp3sA+9/ LKjxnTedX0aygXA6rkpX0Y0FvN/9dfm47+LGq7WAqBOyYTU3E6/+Z72bZoG/cG7ANLxcPool LOrU43oqFnD8QwcN56y4VfFj3/jDF2MX3xu4v2OjglVjMEYHTCxP3mpxesGHuqOit/FR+mF0 MP9JGfj6x+bj/9JMBtCW1bY/aPeMdPGTJvXjGtOVYblGZrSjXRn5++Uuy36CvkcrjuziSDG+ JEexGxczWwN4mrOQWhMT5Jyb+18CO+CWxJfHaYXiLEW7dI1AynL4jjn4W0MSiXpWDUw+fsBO Pk6ah10C4+R1Jc7dyUsKksMfvvhRX1hTIXhth85H16706bneTayZBhlZ/hK18uqTX+s0onG/ m1F3vYvdlE4p2ts1mmixMF7KajN9/E5RQtiSArvKTbfsB6Two4MthIuLuf+M0mI4gPl9SPlf fWCYVPhaU9o83y1KFbD/+lh1pjP7bEu/YudBvz7F2Myjh4/9GUAijrCTNeDTDAgvIJDjXuLX pA== Message-ID: <352ab46c-f5ed-33f4-9dfd-ecf540fb1017@sandeen.net> Date: Tue, 4 Feb 2020 16:20:32 -0600 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:68.0) Gecko/20100101 Thunderbird/68.4.2 MIME-Version: 1.0 In-Reply-To: <20200204210632.GL20628@dread.disaster.area> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-xfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-xfs@vger.kernel.org On 2/4/20 3:06 PM, Dave Chinner wrote: > On Tue, Feb 04, 2020 at 10:08:45AM -0600, Eric Sandeen wrote: >> On 2/4/20 12:21 AM, Christoph Hellwig wrote: >>>> - ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL)); >>>> + ASSERT(xfs_is_ilocked(ip, XFS_ILOCK_EXCL)); >>> >>> I think this is a very bad interface. Either we keep our good old >>> xfs_isilocked that just operates on the inode and lock flags, or >>> we use something that gets the actual lock passed. But an interface >>> that encodes the lock in both the function called and the flags, and >>> one that doesn't follow neither the XFS lock flags conventions nor >>> the core kernel convention is just not very useful. >> >> I think this came out of Dave's suggestion on the previous patchset, >> but I agree with you Chrisoph. Even if there is a future reason to >> split it out into a function for each type, I don't see a reason to >> do it now, and this interface is awkward. >> >> I'd prefer to keep xfs_isilocked() with the current calling convention and >> just change its internals to use lockdep. Dave spotted a bug in the >> current implementation, but I think that can be fixed. >> >> Splitting out the 3 lock testing functions seems to me like complexity >> creep that doesn't need to be in this series. >> >> Dave, thoughts? > > All I care about is that we get rid of the mrlock_t. I'm not > interested in bikeshedding the details to death. I've put my 2c > worth in, if you don't like it, then that's fine and I'm not going > to get upset about that. In the short term I'd suggest something like this. It keeps the helper, but we don't have to change the callsites, and breaking out separate types etc can be done after the mrlock removal patchset is done - in a separate series if/when needed. static inline bool __xfs_rwsem_islocked( struct rw_semaphore *rwsem, bool shared, bool excl) { bool locked = false; if (!rwsem_is_locked(rwsem)) return false; if (!debug_locks) return true; if (shared) locked = lockdep_is_held_type(rwsem, 0); if (excl) locked |= lockdep_is_held_type(rwsem, 1); return locked; } bool xfs_isilocked( struct xfs_inode *ip, uint lock_flags) { if (lock_flags & (XFS_ILOCK_EXCL|XFS_ILOCK_SHARED)) { return __xfs_rwsem_islocked(&ip->i_lock.mr_lock, (lock_flags & XFS_ILOCK_SHARED), (lock_flags & XFS_ILOCK_EXCL)); } if (lock_flags & (XFS_MMAPLOCK_EXCL|XFS_MMAPLOCK_SHARED)) { return __xfs_rwsem_islocked(&ip->i_mmlock.mr_lock, (lock_flags & XFS_MMAPLOCK_SHARED), (lock_flags & XFS_MMAPLOCK_EXCL)); } if (lock_flags & (XFS_IOLOCK_EXCL|XFS_IOLOCK_SHARED)) { return __xfs_rwsem_islocked(&VFS_I(ip)->i_rwsem, (lock_flags & XFS_IOLOCK_SHARED), (lock_flags & XFS_IOLOCK_EXCL)); } } That still has the problem/bug with the existing ASSERT(xfs_isilocked(ip, XFS_IOLOCK_EXCL | XFS_ILOCK_EXCL)); callsite since it doesn't actually test both types but again that is a separate bugfix - it could be changed to accumulate a true/false state for all the flags in the lock_flags argument in another bugfix patch. -Eric