On 2018/9/11 20:57, Trond Myklebust wrote: > On Tue, 2018-09-11 at 20:29 +0800, Kinglong Mee wrote: >> The latest ganesha/gluster supports seek according to, >> >> > https://tools.ietf.org/html/draft-ietf-nfsv4-minorversion2-41#section-15.11 >> >> From the given sa_offset, find the next data_content4 of type >> sa_what >> in the file. If the server can not find a corresponding sa_what, >> then the status will still be NFS4_OK, but sr_eof would be >> TRUE. If >> the server can find the sa_what, then the sr_offset is the start >> of >> that content. If the sa_offset is beyond the end of the file, >> then >> SEEK MUST return NFS4ERR_NXIO. >> >> For a file's filemap as, >> >> Part 1: HOLE 0x0000000000000000 ---> 0x0000000000600000 >> Part 2: DATA 0x0000000000600000 ---> 0x0000000000700000 >> Part 3: HOLE 0x0000000000700000 ---> 0x0000000001000000>> >> SEEK(0x700000, SEEK_DATA) gets result (sr_eof:1, sr_offset:0x70000) >> from ganesha/gluster; >> SEEK(0x700000, SEEK_HOLE) gets result (sr_eof:0, sr_offset:0x70000) >> from ganesha/gluster. >> >> If an application depends the lseek result for data searching, it may >> enter infinite loop. >> >> while (1) { >> next_pos = lseek(fd, cur_pos, seek_type); >> if (seek_type == SEEK_DATA) { >> seek_type = SEEK_HOLE; >> } else { >> seek_type = SEEK_DATA; >> } >> >> if (next_pos == -1) { >> return ; >> >> cur_pos = next_pos; >> } >> >> The lseek syscall always gets 0x70000 from nfs client for those two >> cases, >> but, if underlying filesystem is ext4/f2fs, or the nfs server is >> knfsd, >> the lseek(0x700000, SEEK_DATA) gets ENXIO. >> >> I wanna to know, >> should I fix the ganesha/gluster as knfsd return ENXIO for the first >> case? >> or should I fix the nfs client to return ENXIO for the first case? >> > > It that test correct? The fallback implementation of SEEK_DATA assumes > that the entire file is data, so lseek(SEEK_DATA) on any offset that is > <= eof will be a no-op. The fallback implementation of SEEK_HOLE > assumes that the first hole is at eof. I think that's non-nfsv4.2's logical. > > IOW: unless the initial value for cur_pos is > eof, it looks to me as > if the above test will loop infinitely given any filesystem that > doesn't implement native support for SEEK_DATA/SEEK_HOLE. > No, if underlying filesystem is ext4/f2fs, or the nfs server is knfsd, the last lseek syscall always return ENXIO no matter the cur_pos is > eof or not. A file ends with a hole as, Part 22: DATA 0x0000000006a00000 ---> 0x0000000006afffff Part 23: HOLE 0x0000000006b00000 ---> 0x000000000c7fffff # stat testfile File: testfile Size: 209715200 Blocks: 22640 IO Block: 4096 regular file Device: 807h/2055d Inode: 843122 Links: 2 Access: (0600/-rw-------) Uid: ( 0/ root) Gid: ( 0/ root) Access: 2018-09-11 20:01:41.881227061 +0800 Modify: 2018-09-11 20:01:41.976478311 +0800 Change: 2018-09-11 20:01:41.976478311 +0800 Birth: - # strace filemap testfile ... ... lseek(3, 111149056, SEEK_HOLE) = 112197632 lseek(3, 112197632, SEEK_DATA) = -1 ENXIO (No such device or address) Right now, when knfsd gets the ENXIO error, it returns the error to client directly, and return to syscall. But, ganesha set the sr_eof to true and return NFS4_OK to client as RFC description, nfs client skips the sr_eof and return a bad offset to syscall. thanks, Kinglong Mee
