[PATCH v2 0/3] pnfs/nfsd: have client and server support multiple layout types

[PATCH v2 0/3] pnfs/nfsd: have client and server support multiple layout types

[Jeff Layton]

v2:
- rework Tigran's patch to preserve existing selection behaviour
- simplify layout driver selection by sorting the list

This is v2 of the patchset. Most of the changes are to incorporate
Bruce's suggestions on the client code. Original cover letter follows:

Only lightly tested by mounting a server that sends both flexfiles and
block layouts. The client successfully selected the block layout in most
cases, but if I blacklist blocklayoutdriver then it selects flexfiles
instead.

I'm sending these together, but I'd expect Bruce to pick up the nfsd
patches and Trond or Anna to pick up the client-side ones.

The nfsd patch is based on top of Tom's nfsd flexfile layout patches.

Jeff Layton (3):
  nfsd: allow nfsd to advertise multiple layout types
  pnfs: track multiple layout types in fsinfo structure
  pnfs: add a new mechanism to select a layout driver according to an
    ordered list

 fs/nfs/client.c         |  2 +-
 fs/nfs/nfs4xdr.c        | 23 +++++++---------
 fs/nfs/pnfs.c           | 72 ++++++++++++++++++++++++++++++++++++++++---------
 fs/nfs/pnfs.h           |  4 +--
 fs/nfsd/export.c        |  4 +--
 fs/nfsd/export.h        |  2 +-
 fs/nfsd/nfs4layouts.c   |  6 ++---
 fs/nfsd/nfs4proc.c      |  4 +--
 fs/nfsd/nfs4xdr.c       | 30 ++++++++++-----------
 include/linux/nfs_xdr.h |  7 ++++-
 10 files changed, 101 insertions(+), 53 deletions(-)

-- 
2.5.5

[PATCH v2 1/3] nfsd: allow nfsd to advertise multiple layout types

[Jeff Layton]

If the underlying filesystem supports multiple layout types, then there
is little reason not to advertise that fact to clients and let them
choose what type to use.

Turn the ex_layout_type field into a bitfield. For each supported
layout type, we set a bit in that field. When the client requests a
layout, ensure that the bit for that layout type is set. When the
client requests attributes, send back a list of supported types.

Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
Reviewed-by: Weston Andros Adamson <dros@primarydata.com>
---
 fs/nfsd/export.c      |  4 ++--
 fs/nfsd/export.h      |  2 +-
 fs/nfsd/nfs4layouts.c |  6 +++---
 fs/nfsd/nfs4proc.c    |  4 ++--
 fs/nfsd/nfs4xdr.c     | 30 ++++++++++++++----------------
 5 files changed, 22 insertions(+), 24 deletions(-)

diff --git a/fs/nfsd/export.c b/fs/nfsd/export.c
index b4d84b579f20..f97ba49d5e66 100644
--- a/fs/nfsd/export.c
+++ b/fs/nfsd/export.c
@@ -706,7 +706,7 @@ static void svc_export_init(struct cache_head *cnew, struct cache_head *citem)
 	new->ex_fslocs.locations = NULL;
 	new->ex_fslocs.locations_count = 0;
 	new->ex_fslocs.migrated = 0;
-	new->ex_layout_type = 0;
+	new->ex_layout_types = 0;
 	new->ex_uuid = NULL;
 	new->cd = item->cd;
 }
@@ -731,7 +731,7 @@ static void export_update(struct cache_head *cnew, struct cache_head *citem)
 	item->ex_fslocs.locations_count = 0;
 	new->ex_fslocs.migrated = item->ex_fslocs.migrated;
 	item->ex_fslocs.migrated = 0;
-	new->ex_layout_type = item->ex_layout_type;
+	new->ex_layout_types = item->ex_layout_types;
 	new->ex_nflavors = item->ex_nflavors;
 	for (i = 0; i < MAX_SECINFO_LIST; i++) {
 		new->ex_flavors[i] = item->ex_flavors[i];
diff --git a/fs/nfsd/export.h b/fs/nfsd/export.h
index 2e315072bf3f..730f15eeb7ed 100644
--- a/fs/nfsd/export.h
+++ b/fs/nfsd/export.h
@@ -57,7 +57,7 @@ struct svc_export {
 	struct nfsd4_fs_locations ex_fslocs;
 	uint32_t		ex_nflavors;
 	struct exp_flavor_info	ex_flavors[MAX_SECINFO_LIST];
-	enum pnfs_layouttype	ex_layout_type;
+	u32			ex_layout_types;
 	struct nfsd4_deviceid_map *ex_devid_map;
 	struct cache_detail	*cd;
 };
diff --git a/fs/nfsd/nfs4layouts.c b/fs/nfsd/nfs4layouts.c
index 6d98d16b3354..2be9602b0221 100644
--- a/fs/nfsd/nfs4layouts.c
+++ b/fs/nfsd/nfs4layouts.c
@@ -139,21 +139,21 @@ void nfsd4_setup_layout_type(struct svc_export *exp)
 	 * otherwise advertise the block layout.
 	 */
 #ifdef CONFIG_NFSD_FLEXFILELAYOUT
-	exp->ex_layout_type = LAYOUT_FLEX_FILES;
+	exp->ex_layout_types |= 1 << LAYOUT_FLEX_FILES;
 #endif
 #ifdef CONFIG_NFSD_BLOCKLAYOUT
 	/* overwrite flex file layout selection if needed */
 	if (sb->s_export_op->get_uuid &&
 	    sb->s_export_op->map_blocks &&
 	    sb->s_export_op->commit_blocks)
-		exp->ex_layout_type = LAYOUT_BLOCK_VOLUME;
+		exp->ex_layout_types |= 1 << LAYOUT_BLOCK_VOLUME;
 #endif
 #ifdef CONFIG_NFSD_SCSILAYOUT
 	/* overwrite block layout selection if needed */
 	if (sb->s_export_op->map_blocks &&
 	    sb->s_export_op->commit_blocks &&
 	    sb->s_bdev && sb->s_bdev->bd_disk->fops->pr_ops)
-		exp->ex_layout_type = LAYOUT_SCSI;
+		exp->ex_layout_types |= 1 << LAYOUT_SCSI;
 #endif
 }
 
diff --git a/fs/nfsd/nfs4proc.c b/fs/nfsd/nfs4proc.c
index 2ee2dc170327..719c620753e2 100644
--- a/fs/nfsd/nfs4proc.c
+++ b/fs/nfsd/nfs4proc.c
@@ -1219,12 +1219,12 @@ nfsd4_verify(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
 static const struct nfsd4_layout_ops *
 nfsd4_layout_verify(struct svc_export *exp, unsigned int layout_type)
 {
-	if (!exp->ex_layout_type) {
+	if (!exp->ex_layout_types) {
 		dprintk("%s: export does not support pNFS\n", __func__);
 		return NULL;
 	}
 
-	if (exp->ex_layout_type != layout_type) {
+	if (!(exp->ex_layout_types & (1 << layout_type))) {
 		dprintk("%s: layout type %d not supported\n",
 			__func__, layout_type);
 		return NULL;
diff --git a/fs/nfsd/nfs4xdr.c b/fs/nfsd/nfs4xdr.c
index 9df898ba648f..4d3ae75ad4c8 100644
--- a/fs/nfsd/nfs4xdr.c
+++ b/fs/nfsd/nfs4xdr.c
@@ -2164,22 +2164,20 @@ nfsd4_encode_aclname(struct xdr_stream *xdr, struct svc_rqst *rqstp,
 }
 
 static inline __be32
-nfsd4_encode_layout_type(struct xdr_stream *xdr, enum pnfs_layouttype layout_type)
+nfsd4_encode_layout_types(struct xdr_stream *xdr, u32 layout_types)
 {
-	__be32 *p;
+	__be32		*p;
+	unsigned long	i = hweight_long(layout_types);
 
-	if (layout_type) {
-		p = xdr_reserve_space(xdr, 8);
-		if (!p)
-			return nfserr_resource;
-		*p++ = cpu_to_be32(1);
-		*p++ = cpu_to_be32(layout_type);
-	} else {
-		p = xdr_reserve_space(xdr, 4);
-		if (!p)
-			return nfserr_resource;
-		*p++ = cpu_to_be32(0);
-	}
+	p = xdr_reserve_space(xdr, 4 + 4 * i);
+	if (!p)
+		return nfserr_resource;
+
+	*p++ = cpu_to_be32(i);
+
+	for (i = LAYOUT_NFSV4_1_FILES; i < LAYOUT_TYPE_MAX; ++i)
+		if (layout_types & (1 << i))
+			*p++ = cpu_to_be32(i);
 
 	return 0;
 }
@@ -2754,13 +2752,13 @@ out_acl:
 	}
 #ifdef CONFIG_NFSD_PNFS
 	if (bmval1 & FATTR4_WORD1_FS_LAYOUT_TYPES) {
-		status = nfsd4_encode_layout_type(xdr, exp->ex_layout_type);
+		status = nfsd4_encode_layout_types(xdr, exp->ex_layout_types);
 		if (status)
 			goto out;
 	}
 
 	if (bmval2 & FATTR4_WORD2_LAYOUT_TYPES) {
-		status = nfsd4_encode_layout_type(xdr, exp->ex_layout_type);
+		status = nfsd4_encode_layout_types(xdr, exp->ex_layout_types);
 		if (status)
 			goto out;
 	}
-- 
2.5.5

[PATCH v2 2/3] pnfs: track multiple layout types in fsinfo structure

[Jeff Layton]

From: Jeff Layton <jeff.layton@primarydata.com>

Current NFSv4.1/pNFS client assumes that MDS supports only one layout
type. While it's true for most existing servers, nevertheless, this can
be change in the near future.

For now, this patch just plumbs in the ability to track a list of
layouts in the fsinfo structure. The existing behavior of the client
is preserved, by having it just select the first entry in the list.

Signed-off-by: Tigran Mkrtchyan <tigran.mkrtchyan@desy.de>
Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
---
 fs/nfs/client.c         |  2 +-
 fs/nfs/nfs4xdr.c        | 23 ++++++++++-------------
 fs/nfs/pnfs.c           | 27 ++++++++++++++++-----------
 fs/nfs/pnfs.h           |  4 ++--
 include/linux/nfs_xdr.h |  7 ++++++-
 5 files changed, 35 insertions(+), 28 deletions(-)

diff --git a/fs/nfs/client.c b/fs/nfs/client.c
index 0c96528db94a..067f489aab3f 100644
--- a/fs/nfs/client.c
+++ b/fs/nfs/client.c
@@ -787,7 +787,7 @@ int nfs_probe_fsinfo(struct nfs_server *server, struct nfs_fh *mntfh, struct nfs
 	}
 
 	fsinfo.fattr = fattr;
-	fsinfo.layouttype = 0;
+	memset(fsinfo.layouttype, 0, sizeof(fsinfo.layouttype));
 	error = clp->rpc_ops->fsinfo(server, mntfh, &fsinfo);
 	if (error < 0)
 		goto out_error;
diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index 661e753fe1c9..b2c698499ad9 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -4720,14 +4720,13 @@ static int decode_getfattr(struct xdr_stream *xdr, struct nfs_fattr *fattr,
 }
 
 /*
- * Decode potentially multiple layout types. Currently we only support
- * one layout driver per file system.
+ * Decode potentially multiple layout types.
  */
-static int decode_first_pnfs_layout_type(struct xdr_stream *xdr,
+static int decode_pnfs_layout_types(struct xdr_stream *xdr,
 					 uint32_t *layouttype)
 {
 	__be32 *p;
-	int num;
+	uint32_t num, i;
 
 	p = xdr_inline_decode(xdr, 4);
 	if (unlikely(!p))
@@ -4736,18 +4735,17 @@ static int decode_first_pnfs_layout_type(struct xdr_stream *xdr,
 
 	/* pNFS is not supported by the underlying file system */
 	if (num == 0) {
-		*layouttype = 0;
 		return 0;
 	}
-	if (num > 1)
-		printk(KERN_INFO "NFS: %s: Warning: Multiple pNFS layout "
-			"drivers per filesystem not supported\n", __func__);
+	if (num > NFS_MAX_LAYOUT_TYPES)
+		printk(KERN_INFO "NFS: %s: Warning: Too many (%d) pNFS layout types\n", __func__, num);
 
 	/* Decode and set first layout type, move xdr->p past unused types */
 	p = xdr_inline_decode(xdr, num * 4);
 	if (unlikely(!p))
 		goto out_overflow;
-	*layouttype = be32_to_cpup(p);
+	for(i = 0; i < num && i < NFS_MAX_LAYOUT_TYPES; i++)
+		layouttype[i] = be32_to_cpup(p++);
 	return 0;
 out_overflow:
 	print_overflow_msg(__func__, xdr);
@@ -4767,10 +4765,9 @@ static int decode_attr_pnfstype(struct xdr_stream *xdr, uint32_t *bitmap,
 	if (unlikely(bitmap[1] & (FATTR4_WORD1_FS_LAYOUT_TYPES - 1U)))
 		return -EIO;
 	if (bitmap[1] & FATTR4_WORD1_FS_LAYOUT_TYPES) {
-		status = decode_first_pnfs_layout_type(xdr, layouttype);
+		status = decode_pnfs_layout_types(xdr, layouttype);
 		bitmap[1] &= ~FATTR4_WORD1_FS_LAYOUT_TYPES;
-	} else
-		*layouttype = 0;
+	}
 	return status;
 }
 
@@ -4851,7 +4848,7 @@ static int decode_fsinfo(struct xdr_stream *xdr, struct nfs_fsinfo *fsinfo)
 	status = decode_attr_time_delta(xdr, bitmap, &fsinfo->time_delta);
 	if (status != 0)
 		goto xdr_error;
-	status = decode_attr_pnfstype(xdr, bitmap, &fsinfo->layouttype);
+	status = decode_attr_pnfstype(xdr, bitmap, fsinfo->layouttype);
 	if (status != 0)
 		goto xdr_error;
 
diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index 0c7e0d45a4de..2fc1b9354345 100644
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -102,32 +102,37 @@ unset_pnfs_layoutdriver(struct nfs_server *nfss)
  * Try to set the server's pnfs module to the pnfs layout type specified by id.
  * Currently only one pNFS layout driver per filesystem is supported.
  *
- * @id layout type. Zero (illegal layout type) indicates pNFS not in use.
+ * @ids array of layout types supported by MDS.
  */
 void
 set_pnfs_layoutdriver(struct nfs_server *server, const struct nfs_fh *mntfh,
-		      u32 id)
+		      u32 *ids)
 {
 	struct pnfs_layoutdriver_type *ld_type = NULL;
+	u32 id;
 
-	if (id == 0)
-		goto out_no_driver;
 	if (!(server->nfs_client->cl_exchange_flags &
 		 (EXCHGID4_FLAG_USE_NON_PNFS | EXCHGID4_FLAG_USE_PNFS_MDS))) {
-		printk(KERN_ERR "NFS: %s: id %u cl_exchange_flags 0x%x\n",
-			__func__, id, server->nfs_client->cl_exchange_flags);
+		printk(KERN_ERR "NFS: %s: cl_exchange_flags 0x%x\n",
+			__func__, server->nfs_client->cl_exchange_flags);
 		goto out_no_driver;
 	}
+
+	id = ids[0];
+	if (!id)
+		goto out_no_driver;
+
 	ld_type = find_pnfs_driver(id);
 	if (!ld_type) {
 		request_module("%s-%u", LAYOUT_NFSV4_1_MODULE_PREFIX, id);
 		ld_type = find_pnfs_driver(id);
-		if (!ld_type) {
-			dprintk("%s: No pNFS module found for %u.\n",
-				__func__, id);
-			goto out_no_driver;
-		}
 	}
+
+	if (!ld_type) {
+		dprintk("%s: No pNFS module found for %u.\n", __func__, id);
+		goto out_no_driver;
+	}
+
 	server->pnfs_curr_ld = ld_type;
 	if (ld_type->set_layoutdriver
 	    && ld_type->set_layoutdriver(server, mntfh)) {
diff --git a/fs/nfs/pnfs.h b/fs/nfs/pnfs.h
index b21bd0bee784..500473c87e82 100644
--- a/fs/nfs/pnfs.h
+++ b/fs/nfs/pnfs.h
@@ -236,7 +236,7 @@ void pnfs_get_layout_hdr(struct pnfs_layout_hdr *lo);
 void pnfs_put_lseg(struct pnfs_layout_segment *lseg);
 void pnfs_put_lseg_locked(struct pnfs_layout_segment *lseg);
 
-void set_pnfs_layoutdriver(struct nfs_server *, const struct nfs_fh *, u32);
+void set_pnfs_layoutdriver(struct nfs_server *, const struct nfs_fh *, u32 *);
 void unset_pnfs_layoutdriver(struct nfs_server *);
 void pnfs_generic_pg_init_read(struct nfs_pageio_descriptor *, struct nfs_page *);
 int pnfs_generic_pg_readpages(struct nfs_pageio_descriptor *desc);
@@ -656,7 +656,7 @@ pnfs_wait_on_layoutreturn(struct inode *ino, struct rpc_task *task)
 }
 
 static inline void set_pnfs_layoutdriver(struct nfs_server *s,
-					 const struct nfs_fh *mntfh, u32 id)
+					 const struct nfs_fh *mntfh, u32 *ids)
 {
 }
 
diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
index c304a11b5b1a..4eef590200c3 100644
--- a/include/linux/nfs_xdr.h
+++ b/include/linux/nfs_xdr.h
@@ -125,6 +125,11 @@ struct nfs_fattr {
 		| NFS_ATTR_FATTR_V4_SECURITY_LABEL)
 
 /*
+ * Maximal number of supported layout drivers.
+ */
+#define NFS_MAX_LAYOUT_TYPES 8
+
+/*
  * Info on the file system
  */
 struct nfs_fsinfo {
@@ -139,7 +144,7 @@ struct nfs_fsinfo {
 	__u64			maxfilesize;
 	struct timespec		time_delta; /* server time granularity */
 	__u32			lease_time; /* in seconds */
-	__u32			layouttype; /* supported pnfs layout driver */
+	__u32			layouttype[NFS_MAX_LAYOUT_TYPES]; /* supported pnfs layout driver */
 	__u32			blksize; /* preferred pnfs io block size */
 	__u32			clone_blksize; /* granularity of a CLONE operation */
 };
-- 
2.5.5

[PATCH v2 3/3] pnfs: add a new mechanism to select a layout driver according to an ordered list

[Jeff Layton]

Currently, the layout driver selection code always chooses the first one
from the list. That's not really ideal however, as the server can send
the list of layout types in any order that it likes. It's up to the
client to select the best one for its needs.

This patch adds an ordered list of preferred driver types and has the
selection code sort the list of avaiable layout drivers according to it.
Any unrecognized layout type is sorted to the end of the list.

For now, the order of preference is hardcoded, but it should be possible
to make this configurable in the future.

Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
---
 fs/nfs/pnfs.c | 57 ++++++++++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 50 insertions(+), 7 deletions(-)

diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
index 2fc1b9354345..c31d30f1e5f2 100644
--- a/fs/nfs/pnfs.c
+++ b/fs/nfs/pnfs.c
@@ -99,6 +99,21 @@ unset_pnfs_layoutdriver(struct nfs_server *nfss)
 }
 
 /*
+ * When the server sends a list of layout types, we choose one in the order
+ * given in the list below.
+ *
+ * FIXME: should this list be configurable via module_param or mount option?
+ */
+static const u32 ld_prefs[] = {
+	LAYOUT_SCSI,
+	LAYOUT_BLOCK_VOLUME,
+	LAYOUT_OSD2_OBJECTS,
+	LAYOUT_FLEX_FILES,
+	LAYOUT_NFSV4_1_FILES,
+	0
+};
+
+/*
  * Try to set the server's pnfs module to the pnfs layout type specified by id.
  * Currently only one pNFS layout driver per filesystem is supported.
  *
@@ -110,6 +125,8 @@ set_pnfs_layoutdriver(struct nfs_server *server, const struct nfs_fh *mntfh,
 {
 	struct pnfs_layoutdriver_type *ld_type = NULL;
 	u32 id;
+	int i, j;
+	bool swapped;
 
 	if (!(server->nfs_client->cl_exchange_flags &
 		 (EXCHGID4_FLAG_USE_NON_PNFS | EXCHGID4_FLAG_USE_PNFS_MDS))) {
@@ -118,18 +135,44 @@ set_pnfs_layoutdriver(struct nfs_server *server, const struct nfs_fh *mntfh,
 		goto out_no_driver;
 	}
 
-	id = ids[0];
-	if (!id)
-		goto out_no_driver;
+	/* bubble sort into ld_prefs order */
+	do {
+		swapped = false;
+		for (i = 0; i < (NFS_MAX_LAYOUT_TYPES - 1); i++) {
 
-	ld_type = find_pnfs_driver(id);
-	if (!ld_type) {
-		request_module("%s-%u", LAYOUT_NFSV4_1_MODULE_PREFIX, id);
+			/* If either is zero then we're done with this pass */
+			if (ids[i] == 0 || ids[i + 1] == 0)
+				break;
+
+			for (j = 0; ld_prefs[j] != 0; j++) {
+				/* If we match left entry first, no swap */
+				if (ids[i] == ld_prefs[j])
+					break;
+
+				/* if we match the right, we need to swap */
+				if (ids[i + 1] == ld_prefs[j]) {
+					swap(ids[i], ids[i + 1]);
+					swapped = true;
+					break;
+				}
+			}
+		}
+	} while (swapped);
+
+	for (i = 0; i < NFS_MAX_LAYOUT_TYPES && ids[i] != 0; i++) {
+		id = ids[i];
 		ld_type = find_pnfs_driver(id);
+		if (!ld_type) {
+			request_module("%s-%u", LAYOUT_NFSV4_1_MODULE_PREFIX,
+					id);
+			ld_type = find_pnfs_driver(id);
+		}
+		if (ld_type)
+			break;
 	}
 
 	if (!ld_type) {
-		dprintk("%s: No pNFS module found for %u.\n", __func__, id);
+		dprintk("%s: No pNFS module found!\n", __func__);
 		goto out_no_driver;
 	}
 
-- 
2.5.5

Re: [PATCH v2 3/3] pnfs: add a new mechanism to select a layout driver according to an ordered list

[J. Bruce Fields]

On Thu, Jun 09, 2016 at 08:21:05AM -0400, Jeff Layton wrote:
> Currently, the layout driver selection code always chooses the first one
> from the list. That's not really ideal however, as the server can send
> the list of layout types in any order that it likes. It's up to the
> client to select the best one for its needs.
> 
> This patch adds an ordered list of preferred driver types and has the
> selection code sort the list of avaiable layout drivers according to it.
> Any unrecognized layout type is sorted to the end of the list.
> 
> For now, the order of preference is hardcoded, but it should be possible
> to make this configurable in the future.
> 
> Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
> ---
>  fs/nfs/pnfs.c | 57 ++++++++++++++++++++++++++++++++++++++++++++++++++-------
>  1 file changed, 50 insertions(+), 7 deletions(-)
> 
> diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
> index 2fc1b9354345..c31d30f1e5f2 100644
> --- a/fs/nfs/pnfs.c
> +++ b/fs/nfs/pnfs.c
> @@ -99,6 +99,21 @@ unset_pnfs_layoutdriver(struct nfs_server *nfss)
>  }
>  
>  /*
> + * When the server sends a list of layout types, we choose one in the order
> + * given in the list below.
> + *
> + * FIXME: should this list be configurable via module_param or mount option?
> + */
> +static const u32 ld_prefs[] = {
> +	LAYOUT_SCSI,
> +	LAYOUT_BLOCK_VOLUME,
> +	LAYOUT_OSD2_OBJECTS,
> +	LAYOUT_FLEX_FILES,
> +	LAYOUT_NFSV4_1_FILES,
> +	0
> +};
> +
> +/*
>   * Try to set the server's pnfs module to the pnfs layout type specified by id.
>   * Currently only one pNFS layout driver per filesystem is supported.
>   *
> @@ -110,6 +125,8 @@ set_pnfs_layoutdriver(struct nfs_server *server, const struct nfs_fh *mntfh,
>  {
>  	struct pnfs_layoutdriver_type *ld_type = NULL;
>  	u32 id;
> +	int i, j;
> +	bool swapped;
>  
>  	if (!(server->nfs_client->cl_exchange_flags &
>  		 (EXCHGID4_FLAG_USE_NON_PNFS | EXCHGID4_FLAG_USE_PNFS_MDS))) {
> @@ -118,18 +135,44 @@ set_pnfs_layoutdriver(struct nfs_server *server, const struct nfs_fh *mntfh,
>  		goto out_no_driver;
>  	}
>  
> -	id = ids[0];
> -	if (!id)
> -		goto out_no_driver;
> +	/* bubble sort into ld_prefs order */
> +	do {
> +		swapped = false;
> +		for (i = 0; i < (NFS_MAX_LAYOUT_TYPES - 1); i++) {
>  
> -	ld_type = find_pnfs_driver(id);
> -	if (!ld_type) {
> -		request_module("%s-%u", LAYOUT_NFSV4_1_MODULE_PREFIX, id);
> +			/* If either is zero then we're done with this pass */
> +			if (ids[i] == 0 || ids[i + 1] == 0)
> +				break;
> +
> +			for (j = 0; ld_prefs[j] != 0; j++) {
> +				/* If we match left entry first, no swap */
> +				if (ids[i] == ld_prefs[j])
> +					break;
> +
> +				/* if we match the right, we need to swap */
> +				if (ids[i + 1] == ld_prefs[j]) {
> +					swap(ids[i], ids[i + 1]);
> +					swapped = true;
> +					break;
> +				}
> +			}
> +		}
> +	} while (swapped);

Maybe I'm strange, but, yes, to me this is easier to read as on a first
pass I can just take your word that the above is doing a sort and see
much more quickly what's happening....

Anyway, ACK to the series from me.

--b.

> +
> +	for (i = 0; i < NFS_MAX_LAYOUT_TYPES && ids[i] != 0; i++) {
> +		id = ids[i];
>  		ld_type = find_pnfs_driver(id);
> +		if (!ld_type) {
> +			request_module("%s-%u", LAYOUT_NFSV4_1_MODULE_PREFIX,
> +					id);
> +			ld_type = find_pnfs_driver(id);
> +		}
> +		if (ld_type)
> +			break;
>  	}
>  
>  	if (!ld_type) {
> -		dprintk("%s: No pNFS module found for %u.\n", __func__, id);
> +		dprintk("%s: No pNFS module found!\n", __func__);
>  		goto out_no_driver;
>  	}
>  
> -- 
> 2.5.5

Re: [PATCH v2 3/3] pnfs: add a new mechanism to select a layout driver according to an ordered list

[Jeff Layton]

On Mon, 2016-06-13 at 16:05 -0400, J. Bruce Fields wrote:
> On Thu, Jun 09, 2016 at 08:21:05AM -0400, Jeff Layton wrote:
> > Currently, the layout driver selection code always chooses the first one
> > from the list. That's not really ideal however, as the server can send
> > the list of layout types in any order that it likes. It's up to the
> > client to select the best one for its needs.
> > 
> > This patch adds an ordered list of preferred driver types and has the
> > selection code sort the list of avaiable layout drivers according to it.
> > Any unrecognized layout type is sorted to the end of the list.
> > 
> > For now, the order of preference is hardcoded, but it should be possible
> > to make this configurable in the future.
> > 
> > Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
> > ---
> >  fs/nfs/pnfs.c | 57 ++++++++++++++++++++++++++++++++++++++++++++++++++-------
> >  1 file changed, 50 insertions(+), 7 deletions(-)
> > 
> > diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
> > index 2fc1b9354345..c31d30f1e5f2 100644
> > --- a/fs/nfs/pnfs.c
> > +++ b/fs/nfs/pnfs.c
> > @@ -99,6 +99,21 @@ unset_pnfs_layoutdriver(struct nfs_server *nfss)
> >  }
> >  
> >  /*
> > + * When the server sends a list of layout types, we choose one in the order
> > + * given in the list below.
> > + *
> > + * FIXME: should this list be configurable via module_param or mount option?
> > + */
> > +static const u32 ld_prefs[] = {
> > +	LAYOUT_SCSI,
> > +	LAYOUT_BLOCK_VOLUME,
> > +	LAYOUT_OSD2_OBJECTS,
> > +	LAYOUT_FLEX_FILES,
> > +	LAYOUT_NFSV4_1_FILES,
> > +	0
> > +};
> > +
> > +/*
> >   * Try to set the server's pnfs module to the pnfs layout type specified by id.
> >   * Currently only one pNFS layout driver per filesystem is supported.
> >   *
> > @@ -110,6 +125,8 @@ set_pnfs_layoutdriver(struct nfs_server *server, const struct nfs_fh *mntfh,
> >  {
> >  	struct pnfs_layoutdriver_type *ld_type = NULL;
> >  	u32 id;
> > +	int i, j;
> > +	bool swapped;
> >  
> >  	if (!(server->nfs_client->cl_exchange_flags &
> >  		 (EXCHGID4_FLAG_USE_NON_PNFS | EXCHGID4_FLAG_USE_PNFS_MDS))) {
> > @@ -118,18 +135,44 @@ set_pnfs_layoutdriver(struct nfs_server *server, const struct nfs_fh *mntfh,
> >  		goto out_no_driver;
> >  	}
> >  
> > -	id = ids[0];
> > -	if (!id)
> > -		goto out_no_driver;
> > +	/* bubble sort into ld_prefs order */
> > +	do {
> > +		swapped = false;
> > +		for (i = 0; i < (NFS_MAX_LAYOUT_TYPES - 1); i++) {
> >  
> > -	ld_type = find_pnfs_driver(id);
> > -	if (!ld_type) {
> > -		request_module("%s-%u", LAYOUT_NFSV4_1_MODULE_PREFIX, id);
> > +			/* If either is zero then we're done with this pass */
> > +			if (ids[i] == 0 || ids[i + 1] == 0)
> > +				break;
> > +
> > +			for (j = 0; ld_prefs[j] != 0; j++) {
> > +				/* If we match left entry first, no swap */
> > +				if (ids[i] == ld_prefs[j])
> > +					break;
> > +
> > +				/* if we match the right, we need to swap */
> > +				if (ids[i + 1] == ld_prefs[j]) {
> > +					swap(ids[i], ids[i + 1]);
> > +					swapped = true;
> > +					break;
> > +				}
> > +			}
> > +		}
> > +	} while (swapped);
> 
> Maybe I'm strange, but, yes, to me this is easier to read as on a first
> pass I can just take your word that the above is doing a sort and see
> much more quickly what's happening....
> 

Yeah, it is for me too, actually. Good call on asking for it. ;)

That said, I did notice the code in lib/sort.c after I sent this
series. It might be better to use that instead of this hand-rolled
bubble sort (if only for conciseness -- I doubt it matters for
efficiency).

> Anyway, ACK to the series from me.
> 

Thanks!

> --b.
> 
> > +
> > +	for (i = 0; i < NFS_MAX_LAYOUT_TYPES && ids[i] != 0; i++) {
> > +		id = ids[i];
> >  		ld_type = find_pnfs_driver(id);
> > +		if (!ld_type) {
> > +			request_module("%s-%u", LAYOUT_NFSV4_1_MODULE_PREFIX,
> > +					id);
> > +			ld_type = find_pnfs_driver(id);
> > +		}
> > +		if (ld_type)
> > +			break;
> >  	}
> >  
> >  	if (!ld_type) {
> > -		dprintk("%s: No pNFS module found for %u.\n", __func__, id);
> > +		dprintk("%s: No pNFS module found!\n", __func__);
> >  		goto out_no_driver;
> >  	}
> >  
> > -- 
> > 2.5.5
-- 
Jeff Layton <jlayton@poochiereds.net>

Re: [PATCH v2 3/3] pnfs: add a new mechanism to select a layout driver according to an ordered list

[J. Bruce Fields]

On Mon, Jun 13, 2016 at 09:46:47PM -0400, Jeff Layton wrote:
> On Mon, 2016-06-13 at 16:05 -0400, J. Bruce Fields wrote:
> > On Thu, Jun 09, 2016 at 08:21:05AM -0400, Jeff Layton wrote:
> > > Currently, the layout driver selection code always chooses the first one
> > > from the list. That's not really ideal however, as the server can send
> > > the list of layout types in any order that it likes. It's up to the
> > > client to select the best one for its needs.
> > > 
> > > This patch adds an ordered list of preferred driver types and has the
> > > selection code sort the list of avaiable layout drivers according to it.
> > > Any unrecognized layout type is sorted to the end of the list.
> > > 
> > > For now, the order of preference is hardcoded, but it should be possible
> > > to make this configurable in the future.
> > > 
> > > Signed-off-by: Jeff Layton <jeff.layton@primarydata.com>
> > > ---
> > >  fs/nfs/pnfs.c | 57 ++++++++++++++++++++++++++++++++++++++++++++++++++-------
> > >  1 file changed, 50 insertions(+), 7 deletions(-)
> > > 
> > > diff --git a/fs/nfs/pnfs.c b/fs/nfs/pnfs.c
> > > index 2fc1b9354345..c31d30f1e5f2 100644
> > > --- a/fs/nfs/pnfs.c
> > > +++ b/fs/nfs/pnfs.c
> > > @@ -99,6 +99,21 @@ unset_pnfs_layoutdriver(struct nfs_server *nfss)
> > >  }
> > >  
> > >  /*
> > > + * When the server sends a list of layout types, we choose one in the order
> > > + * given in the list below.
> > > + *
> > > + * FIXME: should this list be configurable via module_param or mount option?
> > > + */
> > > +static const u32 ld_prefs[] = {
> > > +	LAYOUT_SCSI,
> > > +	LAYOUT_BLOCK_VOLUME,
> > > +	LAYOUT_OSD2_OBJECTS,
> > > +	LAYOUT_FLEX_FILES,
> > > +	LAYOUT_NFSV4_1_FILES,
> > > +	0
> > > +};
> > > +
> > > +/*
> > >   * Try to set the server's pnfs module to the pnfs layout type specified by id.
> > >   * Currently only one pNFS layout driver per filesystem is supported.
> > >   *
> > > @@ -110,6 +125,8 @@ set_pnfs_layoutdriver(struct nfs_server *server, const struct nfs_fh *mntfh,
> > >  {
> > >  	struct pnfs_layoutdriver_type *ld_type = NULL;
> > >  	u32 id;
> > > +	int i, j;
> > > +	bool swapped;
> > >  
> > >  	if (!(server->nfs_client->cl_exchange_flags &
> > >  		 (EXCHGID4_FLAG_USE_NON_PNFS | EXCHGID4_FLAG_USE_PNFS_MDS))) {
> > > @@ -118,18 +135,44 @@ set_pnfs_layoutdriver(struct nfs_server *server, const struct nfs_fh *mntfh,
> > >  		goto out_no_driver;
> > >  	}
> > >  
> > > -	id = ids[0];
> > > -	if (!id)
> > > -		goto out_no_driver;
> > > +	/* bubble sort into ld_prefs order */
> > > +	do {
> > > +		swapped = false;
> > > +		for (i = 0; i < (NFS_MAX_LAYOUT_TYPES - 1); i++) {
> > >  
> > > -	ld_type = find_pnfs_driver(id);
> > > -	if (!ld_type) {
> > > -		request_module("%s-%u", LAYOUT_NFSV4_1_MODULE_PREFIX, id);
> > > +			/* If either is zero then we're done with this pass */
> > > +			if (ids[i] == 0 || ids[i + 1] == 0)
> > > +				break;
> > > +
> > > +			for (j = 0; ld_prefs[j] != 0; j++) {
> > > +				/* If we match left entry first, no swap */
> > > +				if (ids[i] == ld_prefs[j])
> > > +					break;
> > > +
> > > +				/* if we match the right, we need to swap */
> > > +				if (ids[i + 1] == ld_prefs[j]) {
> > > +					swap(ids[i], ids[i + 1]);
> > > +					swapped = true;
> > > +					break;
> > > +				}
> > > +			}
> > > +		}
> > > +	} while (swapped);
> > 
> > Maybe I'm strange, but, yes, to me this is easier to read as on a first
> > pass I can just take your word that the above is doing a sort and see
> > much more quickly what's happening....
> > 
> 
> Yeah, it is for me too, actually. Good call on asking for it. ;)
> 
> That said, I did notice the code in lib/sort.c after I sent this
> series. It might be better to use that instead of this hand-rolled
> bubble sort (if only for conciseness -- I doubt it matters for
> efficiency).

Makes sense.  I'll expect a resend of these some day either way, then
I'll probably take the nfsd part if there's no objections....

--b.