2011/10/7 Jan Kara <jack@xxxxxxx>: > Hello, > > On Fri 30-09-11 11:02:34, Ashish Sangwan wrote: >> While mounting UDF media, when the primary AVDP is not found at block 256, >> UDF code tries to read-in the alternate AVDP. >> In the function udf_find_anchor, udf_scan_anchors is called 3 times, where >> each call to udf_scan_anchors read 12 blocks. >> In case there is no alternate AVDP stored, a total of 36 blocks are read >> before mount fails - causing time delay for Mount Failure. >> >> After first call to udf_scan_anchors and before the second call there is >> varconv conversion, for the older drivers, which skips 7 blocks after every >> 32 blocks. What are these older drivers? Do we still require this code? > Frankly, I don't know what are these older drives. The code has been like > this when I started maintaining it and I didn't want to introduce > regressions so I kept the varconv code in. > >> After varconv conversion, why is there a third call to udf_scan_anchors? In >> the 1st call and 3rd call to udf_scan_anchors, exactly same blocks are read, >> so this 3rd call seems to be redundant. > This is not true - the second call uses > udf_variable_to_fixed(sbi->s_last_block) as the last block on the media > while the third call uses sbi->s_last_block as the last block on the media > (both these scans are performed with varconv enabled). Again I have not > seen a drive / medium where this would be needed but I believe original > author had some reason to put the code in. I agree. It would cause side-effect if old code is skipped without knowing author's intent. So It is correct to be kept this like now. > > I agree that the anchor searching code is a pain but that's how the > standard is defined... Actually, proper exception will be needed for metadata very slow loading disc. I will share with you if there is good solution after considering. Thanks. > >> I suggest this modified code for udf_find_anchor :- >> lastblock = >> udf_scan_anchors(sb,udf_variable_to_fixed(sbi->s_last_block),fileset); >> if (lastblock) >> goto out; >> else { >> /* VARCONV didn't help. Clear it. */ >> UDF_CLEAR_FLAG(sb, UDF_FLAG_VARCONV); >> return 0; >> } >> >> Please give your opininon to these 2 above points. If the code change seems >> relevant than I can make patch for it. > > Honza > -- > Jan Kara <jack@xxxxxxx> > SUSE Labs, CR > -- 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