Gang, On Thu, May 4, 2017 at 5:33 AM, Gang He <ghe@xxxxxxxx> wrote: > Hello Guys, > > I found a interesting thing on GFS2 file system, After I did a direct IO write for a whole file, I still saw there were some page caches in this inode. > It looks this GFS2 behavior does not follow file system POSIX semantics, I just want to know this problem belongs to a know issue or we can fix it? > By the way, I did the same testing on EXT4 and OCFS2 file systems, the result looks OK. > I will paste my testing command lines and outputs as below, > > For EXT4 file system, > tb-nd1:/mnt/ext4 # rm -rf f3 > tb-nd1:/mnt/ext4 # dd if=/dev/urandom of=./f3 bs=1M count=4 oflag=direct > 4+0 records in > 4+0 records out > 4194304 bytes (4.2 MB, 4.0 MiB) copied, 0.0393563 s, 107 MB/s > tb-nd1:/mnt/ext4 # vmtouch -v f3 > f3 > [ ] 0/1024 > > Files: 1 > Directories: 0 > Resident Pages: 0/1024 0/4M 0% > Elapsed: 0.000424 seconds > tb-nd1:/mnt/ext4 # > > For OCFS2 file system, > tb-nd1:/mnt/ocfs2 # rm -rf f3 > tb-nd1:/mnt/ocfs2 # dd if=/dev/urandom of=./f3 bs=1M count=4 oflag=direct > 4+0 records in > 4+0 records out > 4194304 bytes (4.2 MB, 4.0 MiB) copied, 0.0592058 s, 70.8 MB/s > tb-nd1:/mnt/ocfs2 # vmtouch -v f3 > f3 > [ ] 0/1024 > > Files: 1 > Directories: 0 > Resident Pages: 0/1024 0/4M 0% > Elapsed: 0.000226 seconds > > For GFS2 file system, > tb-nd1:/mnt/gfs2 # rm -rf f3 > tb-nd1:/mnt/gfs2 # dd if=/dev/urandom of=./f3 bs=1M count=4 oflag=direct > 4+0 records in > 4+0 records out > 4194304 bytes (4.2 MB, 4.0 MiB) copied, 0.0579509 s, 72.4 MB/s > tb-nd1:/mnt/gfs2 # vmtouch -v f3 > f3 > [ oo oOo ] 48/1024 I cannot reproduce, at least not so easily. What kernel version is this? If it's not a mainline kernel, can you reproduce on mainline? Thanks, Andreas
