On 4/24/12 4:28 PM, Andreas Dilger wrote: > On 2012-04-24, at 2:21 PM, Eric Sandeen wrote: >> I know I'm being a little pedantic w/ the late review here.... >> >> It seems like the only differences between ext4_dir_llseek and the old ext4_llseek are these: >> >> 1) For SEEK_END, we now return -EINVAL for a positive offset (i.e. past EOF) >> 2) For SEEK_END, we seek to ext4_get_htree_eof() not to inode->i_size >> 3) For SEEK_SET, we impose different limits for max offset >> - s_maxbytes / ext4_get_htree_eof for !dx/dx, vs. s_bitmap_maxbytes/s_maxbytes >> >> Do any of these changes relate to the hash collision problem? Are any of them uniquely required for ext4, enough to warrant cut & paste of the vfs llseek code (again?) >> >> What I'm getting at is: what are the reasons that we cannot use generic_file_llseek_size(), maybe with a new argument to specify a non-standard location for SEEK_END. Such a change would require a solid explanation, but it'd probably go in if it meant one less seek implementation to worry about. > > So, when we were looking at this code, it makes sense that if dir seek is being done for telldir/seekdir that the parameters for ext4 are hash functions, so they should be compared against hash limits instead of the file size. > > This probably makes sense for other filesystems that use hash cookies instead of byte offsets to have a similar dir seek implementation, but I thought there might be a controversy about this and I'm happy to get it into ext4 as a starting point. That makes sense... but I think the generic code could be expanded to handle this, if we used the existing size parameter to specify max seekable offset in the dir, and a new parameter to cause SEEK_END to behave in a special way (not depending on i_size?) -Eric > Cheers, Andreas > -- > Andreas Dilger Whamcloud, Inc. > Principal Lustre Engineer http://www.whamcloud.com/ > > > > -- 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
