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Re: svn commit: r1296604 - in /subversion/trunk/subversion/libsvn_fs_fs: caching.c fs.h fs_fs.c

From: Philip Martin <philip.martin_at_wandisco.com>
Date: Mon, 05 Mar 2012 13:58:18 +0000

Daniel Shahaf <danielsh_at_elego.de> writes:

> Philip Martin wrote on Mon, Mar 05, 2012 at 12:23:40 +0000:
>> Daniel Shahaf <danielsh_at_elego.de> writes:
>>
>> > You're right, I misread the code: I mistakenly thought line 2867 will
>> > always re-read the revprop-gen file from disk. How about:
>> >
>> > Index: subversion/libsvn_fs_fs/fs_fs.c
>> > ===================================================================
>> > --- subversion/libsvn_fs_fs/fs_fs.c (revision 1297002)
>> > +++ subversion/libsvn_fs_fs/fs_fs.c (working copy)
>> > @@ -583,8 +583,9 @@ with_some_lock_file(svn_fs_t *fs,
>> > fs_fs_data_t *ffd = fs->fsap_data;
>> > if (ffd->format >= SVN_FS_FS__MIN_PACKED_FORMAT)
>> > SVN_ERR(update_min_unpacked_rev(fs, pool));
>> > SVN_ERR(get_youngest(&ffd->youngest_rev_cache, fs->path,
>> > pool));
>> > + SVN_ERR(read_revprop_generation(fs, pool));
>> > err = body(baton, subpool);
>> > }
>> >
>>
>> That looks like it works. But it only works if all writers update the
>> generation file so this whole caching scheme requires an FSFS format
>> bump to exclude 1.7 and earlier.
>
> +1
>
> (It was pointed on IRC, too.)

If we were to clear the cache after taking the write lock, either
unconditionally or if the revprop generation has changed, then we would
become compatible with pre-1.8 style writers.

Of course this does highlight a change in svn_fs_t behaviour. A long
lived svn_fs_t may never see revprop updates as the cache never expires.
The cached values might get pushed out if the process (thead?) reads
other revisions, to get reasonably up-to-date values the caller must not
hold svn_fs_t objects too long.

-- 
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Received on 2012-03-05 14:58:55 CET

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