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. 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. -- Trond Myklebust Linux NFS client maintainer, Hammerspace trond.myklebust@hammerspace.com