On 2014/12/1 23:26, Miklos Szeredi wrote: > On Sat, Nov 29, 2014 at 11:11 AM, hujianyang <hujianyang@xxxxxxxxxx> wrote: >> Hi Miklos, >> >> Sorry for disturb you. I'm confused with *cursor* in struct >> ovl_dir_file. I know this struct ovl_cache_entry *cursor* is >> presented to indicate current pos when performing readdir at >> a MERGE type directory. >> >> Why this additional entry is needed? Can't we use a pointer >> to record which entry is read or is ready for reading? After >> finish reading lower and upper directories, entries in struct >> ovl_dir_cache is stabilized. Changing of directories will >> cause the later .readdir() to create a new ovl_dir_cache but >> the old cache will not be released until all the holders of >> it call .release(). >> >> So I think a pointer points to an entry in the entry list of >> ovl_dir_cache is enough to each process sharing the access >> of the same cache. We don't need to keep and move an special >> entry, *cursor*. That's my thought. > > Cursors are safe against removal of current entry. However, we don't > do that here, AFAICS, so I think you are correct in that the cursor is > not actually needed here. > Thanks~! Do you think it's valuable to discard the using of *cursor* and use a pointer instead? Or maybe we will enable some remove operations for ovl_dir_cache in the future so we should keep this mechanism. What's your opinion? I'd like to change this part and see if the usage of a pointer could speed up .readdir() on a merged directory. Cheers, Hu -- To unsubscribe from this list: send the line "unsubscribe linux-unionfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
