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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <20201103133108.148112-9-wqu@suse.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On 3.11.20 г. 15:30 ч., Qu Wenruo wrote: > For __set_extent_bit(), those parameter are less common for most > callers: > - exclusive_bits > - failed_start > Mostly for extent locking. > > - extent_changeset > For qgroup usage. > > As a common design principle, less common parameters should have their > default values and only callers really need them will set the parameters > to non-default values. > > Sink those parameters into a new structure, extent_io_extra_options. > So most callers won't bother those less used parameters, and make later > expansion easier. > > Signed-off-by: Qu Wenruo IMO I feel this is an overkill, __set_extent_Bit is really some low-level, hidden interface which is being wrapped around by other high-level extent bit manipulation functions. Following this logic I did send today a patch renaming __set_extent_bit to set_extent_bit, essentially removing a level of indirection. Having said that what you are doing right now might make more sense for future changes since you state it's preparatory anyway. But in any case I believe the interface for this function is just broken if we have to resort to such type of refactoring. See below for one idea of extent bits handling. > --- > fs/btrfs/extent-io-tree.h | 22 ++++++++++++++ > fs/btrfs/extent_io.c | 61 ++++++++++++++++++++++++--------------- > 2 files changed, 59 insertions(+), 24 deletions(-) > > diff --git a/fs/btrfs/extent-io-tree.h b/fs/btrfs/extent-io-tree.h > index cab4273ff8d3..c93065794567 100644 > --- a/fs/btrfs/extent-io-tree.h > +++ b/fs/btrfs/extent-io-tree.h > @@ -82,6 +82,28 @@ struct extent_state { > #endif > }; > > +/* > + * Extra options for extent io tree operations. > + * > + * All of these options are initialized to 0/false/NULL by default, > + * and most callers should utilize the wrappers other than the extra options. > + */ > +struct extent_io_extra_options { > + /* > + * For __set_extent_bit(), to return -EEXIST when hit an extent with > + * @excl_bits set, and update @excl_failed_start. > + * Utizlied by EXTENT_LOCKED wrappers. nit: excl_bits can be removed if we simply check for the presence of EXTENT_LOCKED in 'bits' and if the result is true then also check if the found extent has EXTENT_LOCKED if it does -> return the failure_start, that we we can get rid of 'excl_bits'. All uses of EXTENT_LOCKED is via lock_extent_range except the one in the private failure tree but I believe it should be ok. I had a crazy idea to overload cached_state to return the failure range and use it in lock_extent_bit but that makes it rather messy. ... > + */ > + u32 excl_bits; > + u64 excl_failed_start; > + > + /* > + * For __set/__clear_extent_bit() to record how many bytes is modified. > + * For qgroup related functions. > + */ > + struct extent_changeset *changeset; > +}; > + > int __init extent_state_cache_init(void); > void __cold extent_state_cache_exit(void); >