On Tue, Jun 14, 2011 at 11:53 AM, Peng Tao <bergwolf@xxxxxxxxx> wrote: > On Tue, Jun 14, 2011 at 10:05 PM, Fred Isaman <iisaman@xxxxxxxxxx> wrote: >> On Tue, Jun 14, 2011 at 7:01 AM, <tao.peng@xxxxxxx> wrote: >>> Hi, Fred, >>> >>>> -----Original Message----- >>>> From: linux-nfs-owner@xxxxxxxxxxxxxxx [mailto:linux-nfs-owner@xxxxxxxxxxxxxxx] >>>> On Behalf Of Fred Isaman >>>> Sent: Monday, June 13, 2011 10:44 PM >>>> To: Jim Rees >>>> Cc: linux-nfs@xxxxxxxxxxxxxxx; peter honeyman >>>> Subject: Re: [PATCH 04/34] pnfs: hook nfs_write_begin/end to allow layout driver >>>> manipulation >>>> >>>> On Sun, Jun 12, 2011 at 7:43 PM, Jim Rees <rees@xxxxxxxxx> wrote: >>>> > From: Peng Tao <bergwolf@xxxxxxxxx> >>>> > >>>> > Signed-off-by: Fred Isaman <iisaman@xxxxxxxxxxxxxx> >>>> > Signed-off-by: Benny Halevy <bhalevy@xxxxxxxxxxx> >>>> > Reported-by: Alexandros Batsakis <batsakis@xxxxxxxxxx> >>>> > Signed-off-by: Andy Adamson <andros@xxxxxxxxxx> >>>> > Signed-off-by: Fred Isaman <iisaman@xxxxxxxxxx> >>>> > Signed-off-by: Benny Halevy <bhalevy@xxxxxxxxxxx> >>>> > Signed-off-by: Peng Tao <bergwolf@xxxxxxxxx> >>>> > --- >>>> > fs/nfs/file.c | 26 ++++++++++- >>>> > fs/nfs/pnfs.c | 41 +++++++++++++++++ >>>> > fs/nfs/pnfs.h | 115 >>>> ++++++++++++++++++++++++++++++++++++++++++++++++ >>>> > fs/nfs/write.c | 12 +++-- >>>> > include/linux/nfs_fs.h | 3 +- >>>> > 5 files changed, 189 insertions(+), 8 deletions(-) >>>> > >>>> > diff --git a/fs/nfs/file.c b/fs/nfs/file.c >>>> > index 2f093ed..1768762 100644 >>>> > --- a/fs/nfs/file.c >>>> > +++ b/fs/nfs/file.c >>>> > @@ -384,12 +384,15 @@ static int nfs_write_begin(struct file *file, struct >>>> address_space *mapping, >>>> > pgoff_t index = pos >> PAGE_CACHE_SHIFT; >>>> > struct page *page; >>>> > int once_thru = 0; >>>> > + struct pnfs_layout_segment *lseg; >>>> > >>>> > dfprintk(PAGECACHE, "NFS: write_begin(%s/%s(%ld), %u@%lld)\n", >>>> > file->f_path.dentry->d_parent->d_name.name, >>>> > file->f_path.dentry->d_name.name, >>>> > mapping->host->i_ino, len, (long long) pos); >>>> > - >>>> > + lseg = pnfs_update_layout(mapping->host, >>>> > + nfs_file_open_context(file), >>>> > + pos, len, IOMODE_RW, GFP_NOFS); >>>> >>>> >>>> This looks like it is left over from before the rearrangements done to >>>> where pnfs_update_layout. >>>> In particular, we don't want to hold the reference on the lseg from >>>> here until flush time. And there >>>> seems to be no reason to. If the client needs a layout to deal with >>>> read-in here, it should instead >>>> trigger the nfs_want_read_modify_write clause. >>> Yes, you are right. Directly calling pnfs_update_layout here can be avoided. >>> But it seems triggering nfs_want_read_modify_write will acquire a read-only layout segment via readpage code path. >>> For write, client will need a read-write layout segment so it would mean two layoutget for each new segment (one in nfs_readpage and one at flush time). It may not be good for performance. >>> Does current generic code have method to avoid this? >>> >>> Thanks, >>> Tao >>> >> >> No. However, note that this only hits in the case where you are doing >> subpage writes. > block layout driver need the segment to determine if it should dirty > other pages in the same fsblock based on if it is a first write to an > INVALID extent. So it still hits whenever an fsblock is dirtied for > the first time. > > Thanks, > Tao > Why can't this be delayed until flush? Fred -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
