[PATCH 1/3] NFSv4/flexfiles: report the intended opnum when DS connection setup fails

When nfs4_ff_layout_prepare_ds() cannot establish a connection to a
data server, it records a device error with opnum OP_ILLEGAL, since no
operation ever made it to the wire.  But servers can use the ff_ioerr4
opnum to distinguish failed read-class operations from write-class
operations when deciding how to recover the affected mirror -- a mirror
that may have missed writes needs to be brought back in sync, while one
that merely failed to serve a read does not.  OP_ILLEGAL gives the
server nothing to act on.

Every caller of nfs4_ff_layout_prepare_ds() knows which operation it
was preparing to send, and the existing fail_return argument already
divides the callers along the same boundary (false for READ, true for
WRITE and COMMIT).  Replace the boolean with the intended opnum, derive
the layout return decision from it, and report it in the tracked device
error instead of OP_ILLEGAL.

Assisted-by: Claude:claude-fable-5
Signed-off-by: Benjamin Coddington <bcodding-F/[email protected]>
---
 fs/nfs/flexfilelayout/flexfilelayout.c    | 10 +++++-----
 fs/nfs/flexfilelayout/flexfilelayout.h    |  2 +-
 fs/nfs/flexfilelayout/flexfilelayoutdev.c | 14 ++++++++------
 3 files changed, 14 insertions(+), 12 deletions(-)

diff --git a/fs/nfs/flexfilelayout/flexfilelayout.c b/fs/nfs/flexfilelayout/flexfilelayout.c
index 7fe8b91fa47c..2c30e62881a1 100644
--- a/fs/nfs/flexfilelayout/flexfilelayout.c
+++ b/fs/nfs/flexfilelayout/flexfilelayout.c
@@ -893,7 +893,7 @@ ff_layout_choose_ds_for_read(struct pnfs_layout_segment *lseg,
 			fls->stripe_unit,
 			fls->mirror_array[idx]->dss_count,
 			offset);
-		ds = nfs4_ff_layout_prepare_ds(lseg, mirror, *dss_id, false);
+		ds = nfs4_ff_layout_prepare_ds(lseg, mirror, *dss_id, OP_READ);
 		if (IS_ERR(ds))
 			continue;
 
@@ -1135,7 +1135,7 @@ ff_layout_pg_init_write(struct nfs_pageio_descriptor *pgio,
 			mirror->dss_count,
 			req_offset(req));
 		ds = nfs4_ff_layout_prepare_ds(pgio->pg_lseg, mirror,
-					       dss_id, true);
+					       dss_id, OP_WRITE);
 		if (IS_ERR(ds)) {
 			if (!ff_layout_no_fallback_to_mds(pgio->pg_lseg))
 				goto out_mds;
@@ -2184,7 +2184,7 @@ ff_layout_read_pagelist(struct nfs_pgio_header *hdr)
 		FF_LAYOUT_LSEG(lseg)->stripe_unit,
 		mirror->dss_count,
 		offset);
-	ds = nfs4_ff_layout_prepare_ds(lseg, mirror, dss_id, false);
+	ds = nfs4_ff_layout_prepare_ds(lseg, mirror, dss_id, OP_READ);
 	if (IS_ERR(ds)) {
 		ds_fatal_error = nfs_error_is_fatal(PTR_ERR(ds));
 		goto out_failed;
@@ -2275,7 +2275,7 @@ ff_layout_write_pagelist(struct nfs_pgio_header *hdr, int sync)
 		FF_LAYOUT_LSEG(lseg)->stripe_unit,
 		mirror->dss_count,
 		offset);
-	ds = nfs4_ff_layout_prepare_ds(lseg, mirror, dss_id, true);
+	ds = nfs4_ff_layout_prepare_ds(lseg, mirror, dss_id, OP_WRITE);
 	if (IS_ERR(ds)) {
 		ds_fatal_error = nfs_error_is_fatal(PTR_ERR(ds));
 		goto out_failed;
@@ -2376,7 +2376,7 @@ static int ff_layout_initiate_commit(struct nfs_commit_data *data, int how)
 	idx = calc_mirror_idx_from_commit(lseg, data->ds_commit_index);
 	mirror = FF_LAYOUT_COMP(lseg, idx);
 	dss_id = calc_dss_id_from_commit(lseg, data->ds_commit_index);
-	ds = nfs4_ff_layout_prepare_ds(lseg, mirror, dss_id, true);
+	ds = nfs4_ff_layout_prepare_ds(lseg, mirror, dss_id, OP_COMMIT);
 	if (IS_ERR(ds))
 		goto out_err;
 
diff --git a/fs/nfs/flexfilelayout/flexfilelayout.h b/fs/nfs/flexfilelayout/flexfilelayout.h
index a5bd00f69e82..8e3a1e45ea68 100644
--- a/fs/nfs/flexfilelayout/flexfilelayout.h
+++ b/fs/nfs/flexfilelayout/flexfilelayout.h
@@ -252,7 +252,7 @@ struct nfs4_pnfs_ds *
 nfs4_ff_layout_prepare_ds(struct pnfs_layout_segment *lseg,
 			  struct nfs4_ff_layout_mirror *mirror,
 			  u32 dss_id,
-			  bool fail_return);
+			  enum nfs_opnum4 opnum);
 
 struct rpc_clnt *
 nfs4_ff_find_or_create_ds_client(struct nfs4_ff_layout_mirror *mirror,
diff --git a/fs/nfs/flexfilelayout/flexfilelayoutdev.c b/fs/nfs/flexfilelayout/flexfilelayoutdev.c
index 8be5c730e101..5920ba529a0b 100644
--- a/fs/nfs/flexfilelayout/flexfilelayoutdev.c
+++ b/fs/nfs/flexfilelayout/flexfilelayoutdev.c
@@ -359,7 +359,7 @@ ff_layout_init_mirror_ds(struct pnfs_layout_hdr *lo,
  * @lseg: the layout segment we're operating on
  * @mirror: layout mirror describing the DS to use
  * @dss_id: DS stripe id to select stripe to use
- * @fail_return: return layout on connect failure?
+ * @opnum: operation this connection is being prepared for
  *
  * Try to prepare a DS connection to accept an RPC call. This involves
  * selecting a mirror to use and connecting the client to it if it's not
@@ -367,8 +367,10 @@ ff_layout_init_mirror_ds(struct pnfs_layout_hdr *lo,
  *
  * Since we only need a single functioning mirror to satisfy a read, we don't
  * want to return the layout if there is one. For writes though, any down
- * mirror should result in a LAYOUTRETURN. @fail_return is how we distinguish
- * between the two cases.
+ * mirror should result in a LAYOUTRETURN. @opnum is how we distinguish
+ * between the two cases. On failure, @opnum is also reported in the tracked
+ * device error so that the server can tell which class of I/O the client
+ * was unable to send to the mirror.
  *
  * Returns a pointer to a connected DS object on success or NULL on failure.
  */
@@ -376,7 +378,7 @@ struct nfs4_pnfs_ds *
 nfs4_ff_layout_prepare_ds(struct pnfs_layout_segment *lseg,
 			  struct nfs4_ff_layout_mirror *mirror,
 			  u32 dss_id,
-			  bool fail_return)
+			  enum nfs_opnum4 opnum)
 {
 	struct nfs4_pnfs_ds *ds;
 	struct inode *ino = lseg->pls_layout->plh_inode;
@@ -423,9 +425,9 @@ nfs4_ff_layout_prepare_ds(struct pnfs_layout_segment *lseg,
 	ff_layout_track_ds_error(FF_LAYOUT_FROM_HDR(lseg->pls_layout),
 				 mirror, dss_id, lseg->pls_range.offset,
 				 lseg->pls_range.length, NFS4ERR_NXIO,
-				 OP_ILLEGAL, GFP_NOIO);
+				 opnum, GFP_NOIO);
 	ff_layout_send_layouterror(lseg);
-	if (fail_return || !ff_layout_has_available_ds(lseg))
+	if (opnum != OP_READ || !ff_layout_has_available_ds(lseg))
 		pnfs_error_mark_layout_for_return(ino, lseg);
 	ds = ERR_PTR(status);
 out:
-- 
2.53.0