Am 09.05.2016 um 00:18 schrieb NeilBrown: >> The biggest problem I see is that UBIFS does not really support telldir() >> and seekdir(). >> Directory offsets in UBIFS are plain hash values, so telldir()/seekdir() won't >> correctly work if UBIFS faces hash collisions. >> Currently UBIFS implements a hack which stores the UBIFS dent object into >> file->private_data such that consecutive readdir()s are guaranteed to work. >> A comment on UBIFS's readdir states: >> * This means that UBIFS cannot support NFS which requires full >> * 'seekdir()'/'telldir()' support. >> >> Is this still true? Maybe we can have NFS even if it is not perfect in >> terms of performance. > > How big are your hashes? > ext3 messed up their readdir/telldir design too so they don't have > guaranteed unique keys. > When using 32bit hashes you can definitely get problems with > collisions. I have not heard of problems with 64bit hashes. > > I may have the details slightly wrong, but as I recall non-uniqueness of > cookies only causes a problem when the last cookie returned in a READDIR > reply matches the first cookie returned in reply to the next readdir. > So non-uniqueness is only a problem when it aligns badly. UBIFS is using 32bit hashes, r5 hash from reiserfs. ;-\ Thanks, //richard -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
