nfs: add support for multiple nfs reqs per page
Add "page groups" - a circular list of nfs requests (struct nfs_page)
that all reference the same page. This gives nfs read and write paths
the ability to account for sub-page regions independently. This
somewhat follows the design of struct buffer_head's sub-page
accounting.
Only "head" requests are ever added/removed from the inode list in
the buffered write path. "head" and "sub" requests are treated the
same through the read path and the rest of the write/commit path.
Requests are given an extra reference across the life of the list.
Page groups are never rejoined after being split. If the read/write
request fails and the client falls back to another path (ie revert
to MDS in PNFS case), the already split requests are pushed through
the recoalescing code again, which may split them further and then
coalesce them into properly sized requests on the wire. Fragmentation
shouldn't be a problem with the current design, because we flush all
requests in page group when a non-contiguous request is added, so
the only time resplitting should occur is on a resend of a read or
write.
This patch lays the groundwork for sub-page splitting, but does not
actually do any splitting. For now all page groups have one request
as pg_test functions don't yet split pages. There are several related
patches that are needed support multiple requests per page group.
Signed-off-by: Weston Andros Adamson <dros@primarydata.com>
Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com>
diff --git a/fs/nfs/write.c b/fs/nfs/write.c
index e773df2..d0f30f1 100644
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -367,6 +367,8 @@
{
struct nfs_inode *nfsi = NFS_I(inode);
+ WARN_ON_ONCE(req->wb_this_page != req);
+
/* Lock the request! */
nfs_lock_request(req);
@@ -383,6 +385,7 @@
set_page_private(req->wb_page, (unsigned long)req);
}
nfsi->npages++;
+ set_bit(PG_INODE_REF, &req->wb_flags);
kref_get(&req->wb_kref);
spin_unlock(&inode->i_lock);
}
@@ -567,6 +570,7 @@
{
struct nfs_commit_info cinfo;
unsigned long bytes = 0;
+ bool do_destroy;
if (test_bit(NFS_IOHDR_REDO, &hdr->flags))
goto out;
@@ -596,6 +600,7 @@
next:
nfs_unlock_request(req);
nfs_end_page_writeback(req->wb_page);
+ do_destroy = !test_bit(NFS_IOHDR_NEED_COMMIT, &hdr->flags);
nfs_release_request(req);
}
out:
@@ -700,6 +705,10 @@
if (req == NULL)
goto out_unlock;
+ /* should be handled by nfs_flush_incompatible */
+ WARN_ON_ONCE(req->wb_head != req);
+ WARN_ON_ONCE(req->wb_this_page != req);
+
rqend = req->wb_offset + req->wb_bytes;
/*
* Tell the caller to flush out the request if
@@ -761,7 +770,7 @@
req = nfs_try_to_update_request(inode, page, offset, bytes);
if (req != NULL)
goto out;
- req = nfs_create_request(ctx, page, offset, bytes);
+ req = nfs_create_request(ctx, page, NULL, offset, bytes);
if (IS_ERR(req))
goto out;
nfs_inode_add_request(inode, req);
@@ -805,6 +814,8 @@
return 0;
l_ctx = req->wb_lock_context;
do_flush = req->wb_page != page || req->wb_context != ctx;
+ /* for now, flush if more than 1 request in page_group */
+ do_flush |= req->wb_this_page != req;
if (l_ctx && ctx->dentry->d_inode->i_flock != NULL) {
do_flush |= l_ctx->lockowner.l_owner != current->files
|| l_ctx->lockowner.l_pid != current->tgid;