On Dec 29, 2008 21:47 +0800, Peng tao wrote: > I got a question about this. > Since htree is a potential limitation for subdirectories. Is there a > reason why EXT4_LINK_MAX is applied when fs hasn't dir_index but > ignored when fs has dir_index(by the following code)? > > #define is_dx(dir) (EXT4_HAS_COMPAT_FEATURE(dir->i_sb, \ > EXT4_FEATURE_COMPAT_DIR_INDEX) && \ > (EXT4_I(dir)->i_flags & EXT4_INDEX_FL)) > #define EXT4_DIR_LINK_MAX(dir) (!is_dx(dir) && (dir)->i_nlink >= EXT4_LINK_MAX) Because without the dir_index feature the largest usable directory size is only about 10k-20k files before the O(n^2) insertion performance is so bad that the directory is useless. > On Wed, Dec 24, 2008 at 9:18 AM, Zhang Xiliang > <zhangxiliang@xxxxxxxxxxxxxx> wrote: > > Theodore Tso 写道: > > > >> > >> So that's not it. The problem is that indexed diretories have a limit > >> that only allows the trees to be two levels deep. The fanout is > >> normally big enough that this is effectively not a problem, but if you > >> use very long filenames, and a 1k blocksize, you will run into this > >> limit much more quickly. So the problem is not the number of sub > >> directories, but the maximum depth of the htree allowed in Daniel > >> Phillips' relatively restricted implementation. Note that with a 4k > >> block filesystem, the limits get expanded by a factor of 4 cubed, or > >> 64. And most of the time users aren't maximal length named directory > >> entries, which further pushes the limit out in the normal case. > >> > >> It in theory would be possible to relax this restriction, using a more > >> advanced htree implementation and a feature flag to allow backwards > >> compatibility with older kernels that only support the maximal depth. > >> Andreas has a prototype kernel implementation which in theory could be > >> added to ext4. It hasn't been high on my priority list to complete, > >> but if someone else really finds this limit to be annoying, it is a > >> project they might try to complete. > >> > >> Were you writing this test program because this is a realistic > >> situation for your application, or just to explore the limits of ext4? > >> > > > > Thanks for explanation. > > > > I see the limit of ext4 subdirectory. The test program originally tests it. > > But I fail and find the limit of the htree. > > > > I think it may be annoying. Somebody may be puzzled for the two limits. > > The limit of the htree should be greater than the limit of ext4 > > subdirectory. > > > > -- > > Regards > > Zhang Xiliang > > > > -- > > To unsubscribe from this list: send the line "unsubscribe linux-ext4" in > > the body of a message to majordomo@xxxxxxxxxxxxxxx > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > > > > > -- > Cheers, > > Bergwolf > > ................ > Rodney Dangerfield - "The way my luck is running, if I was a > politician I would be honest." > N?????r??y????b?X??ǧv?^?){.n?+????{?{x?{ay? ʇڙ?,j??f???h???z? ?w??? ???j:+v???w?j?m????????zZ+?????ݢj"??! Cheers, Andreas -- Andreas Dilger Sr. Staff Engineer, Lustre Group Sun Microsystems of Canada, Inc. -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
