diff mbox series

[02/14] lustre: llite: change how "dump_page_cache" walks a hash table

Message ID 1546810607-6348-3-git-send-email-jsimmons@infradead.org (mailing list archive)
State New, archived
Headers show
Series lustre: fixes for many test failures | expand

Commit Message

James Simmons Jan. 6, 2019, 9:36 p.m. UTC 
From: NeilBrown <neilb@suse.com>

The "dump_page_cache" seq_file currently tries to encode
a location in the hash table into a 64bit file index so that
the seq_file can seek to any location.

This is not necessary with the current implementation of seq_file.
seq_file performs any seeks needed itself by rewinding and calling
->next and ->show until the required index is reached.

The required behaviour of ->next is that it always returns the next
object after the last one returned by either ->start or ->next.
It can ignore the ppos, but should increment it.

The required behaviour of ->start is one of:
1/ if *ppos is 0, then return the first object
2/ if *ppos is the same value that was passed to the most recent call
   to either ->start or ->next, then return the same object again
3/ if *ppos is anything else, return the next object after the most
   recently returned one.

To implement this we store a vvp_pgcache_id (index into hash table)
in the seq_private data structure, and also store 'prev_pos' as the
last value passed to either ->start or ->next.

We remove all converstion of an id to a pos, and any limits on the
size of the vpi_depth.

vvp_pgcache_obj_get() is changed to ignore dying objects so that
vvp_pgcache_obj only returns NULL when it reaches the end of a hash
chain, and so vpi_bucket needs to be incremented.

A reference to the current ->clob pointer is now kept as long as we
are iterating over the pages in a given object, so we don't have to
try to find it again (and possibly fail) for each page.

And the ->start and ->next functions are changed as described above.

Signed-off-by: NeilBrown <neilb@suse.com>
Signed-off-by: James Simmons <uja.ornl@yahoo.com>
WC-bug-id: https://jira.whamcloud.com/browse/LU-8066
Reviewed-on: https://review.whamcloud.com/33011
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
---
 drivers/staging/lustre/lustre/llite/vvp_dev.c | 173 ++++++++++++--------------
 1 file changed, 78 insertions(+), 95 deletions(-)
diff mbox series

Patch

diff --git a/drivers/staging/lustre/lustre/llite/vvp_dev.c b/drivers/staging/lustre/lustre/llite/vvp_dev.c
index 8cc981b..4e55599 100644
--- a/drivers/staging/lustre/lustre/llite/vvp_dev.c
+++ b/drivers/staging/lustre/lustre/llite/vvp_dev.c
@@ -366,22 +366,6 @@  int cl_sb_fini(struct super_block *sb)
  *
  ****************************************************************************/
 
-/*
- * To represent contents of a page cache as a byte stream, following
- * information if encoded in 64bit offset:
- *
- *       - file hash bucket in lu_site::ls_hash[]       28bits
- *
- *       - how far file is from bucket head	      4bits
- *
- *       - page index				   32bits
- *
- * First two data identify a file in the cache uniquely.
- */
-
-#define PGC_OBJ_SHIFT (32 + 4)
-#define PGC_DEPTH_SHIFT (32)
-
 struct vvp_pgcache_id {
 	unsigned int		 vpi_bucket;
 	unsigned int		 vpi_depth;
@@ -396,37 +380,26 @@  struct vvp_seq_private {
 	struct lu_env		*vsp_env;
 	u16			vsp_refcheck;
 	struct cl_object	*vsp_clob;
+	struct vvp_pgcache_id	vsp_id;
+	/*
+	 * prev_pos is the 'pos' of the last object returned
+	 * by ->start of ->next.
+	 */
+	loff_t			vsp_prev_pos;
 };
 
-static void vvp_pgcache_id_unpack(loff_t pos, struct vvp_pgcache_id *id)
-{
-	BUILD_BUG_ON(sizeof(pos) != sizeof(__u64));
-
-	id->vpi_index  = pos & 0xffffffff;
-	id->vpi_depth  = (pos >> PGC_DEPTH_SHIFT) & 0xf;
-	id->vpi_bucket = (unsigned long long)pos >> PGC_OBJ_SHIFT;
-}
-
-static loff_t vvp_pgcache_id_pack(struct vvp_pgcache_id *id)
-{
-	return
-		((__u64)id->vpi_index) |
-		((__u64)id->vpi_depth  << PGC_DEPTH_SHIFT) |
-		((__u64)id->vpi_bucket << PGC_OBJ_SHIFT);
-}
-
 static int vvp_pgcache_obj_get(struct cfs_hash *hs, struct cfs_hash_bd *bd,
 			       struct hlist_node *hnode, void *data)
 {
 	struct vvp_pgcache_id   *id  = data;
 	struct lu_object_header *hdr = cfs_hash_object(hs, hnode);
 
-	if (id->vpi_curdep-- > 0)
-		return 0; /* continue */
-
 	if (lu_object_is_dying(hdr))
 		return 1;
 
+	if (id->vpi_curdep-- > 0)
+		return 0; /* continue */
+
 	cfs_hash_get(hs, hnode);
 	id->vpi_obj = hdr;
 	return 1;
@@ -438,7 +411,6 @@  static struct cl_object *vvp_pgcache_obj(const struct lu_env *env,
 {
 	LASSERT(lu_device_is_cl(dev));
 
-	id->vpi_depth &= 0xf;
 	id->vpi_obj    = NULL;
 	id->vpi_curdep = id->vpi_depth;
 
@@ -453,55 +425,42 @@  static struct cl_object *vvp_pgcache_obj(const struct lu_env *env,
 			return lu2cl(lu_obj);
 		}
 		lu_object_put(env, lu_object_top(id->vpi_obj));
-
-	} else if (id->vpi_curdep > 0) {
-		id->vpi_depth = 0xf;
 	}
 	return NULL;
 }
 
-static struct page *vvp_pgcache_find(const struct lu_env *env,
-				     struct lu_device *dev,
-				     struct cl_object **clobp, loff_t *pos)
+static struct page *vvp_pgcache_current(struct vvp_seq_private *priv)
 {
-	struct cl_object     *clob;
-	struct lu_site       *site;
-	struct vvp_pgcache_id id;
-
-	site = dev->ld_site;
-	vvp_pgcache_id_unpack(*pos, &id);
+	struct lu_device *dev = &priv->vsp_sbi->ll_cl->cd_lu_dev;
 
 	while (1) {
-		if (id.vpi_bucket >= CFS_HASH_NHLIST(site->ls_obj_hash))
-			return NULL;
-		clob = vvp_pgcache_obj(env, dev, &id);
-		if (clob) {
-			struct inode *inode = vvp_object_inode(clob);
-			struct page *vmpage;
-			int nr;
-
-			nr = find_get_pages_contig(inode->i_mapping,
-						   id.vpi_index, 1, &vmpage);
-			if (nr > 0) {
-				id.vpi_index = vmpage->index;
-				/* Cant support over 16T file */
-				if (vmpage->index <= 0xffffffff) {
-					*clobp = clob;
-					*pos = vvp_pgcache_id_pack(&id);
-					return vmpage;
-				}
-				put_page(vmpage);
-			}
-
-			lu_object_ref_del(&clob->co_lu, "dump", current);
-			cl_object_put(env, clob);
+		struct inode *inode;
+		struct page *vmpage;
+		int nr;
+
+		if (!priv->vsp_clob) {
+			struct cl_object *clob;
+
+			while ((clob = vvp_pgcache_obj(priv->vsp_env, dev, &priv->vsp_id)) == NULL &&
+			       ++(priv->vsp_id.vpi_bucket) < CFS_HASH_NHLIST(dev->ld_site->ls_obj_hash))
+				priv->vsp_id.vpi_depth = 0;
+			if (!clob)
+				return NULL;
+			priv->vsp_clob = clob;
+			priv->vsp_id.vpi_index = 0;
+		}
+
+		inode = vvp_object_inode(priv->vsp_clob);
+		nr = find_get_pages_contig(inode->i_mapping, priv->vsp_id.vpi_index, 1, &vmpage);
+		if (nr > 0) {
+			priv->vsp_id.vpi_index = vmpage->index;
+			return vmpage;
 		}
-		/* to the next object. */
-		++id.vpi_depth;
-		id.vpi_depth &= 0xf;
-		if (id.vpi_depth == 0 && ++id.vpi_bucket == 0)
-			return NULL;
-		id.vpi_index = 0;
+		lu_object_ref_del(&priv->vsp_clob->co_lu, "dump", current);
+		cl_object_put(priv->vsp_env, priv->vsp_clob);
+		priv->vsp_clob = NULL;
+		priv->vsp_id.vpi_index = 0;
+		priv->vsp_id.vpi_depth++;
 	}
 }
 
@@ -559,38 +518,55 @@  static int vvp_pgcache_show(struct seq_file *f, void *v)
 	} else {
 		seq_puts(f, "missing\n");
 	}
-	lu_object_ref_del(&priv->vsp_clob->co_lu, "dump", current);
-	cl_object_put(priv->vsp_env, priv->vsp_clob);
 
 	return 0;
 }
 
+static void vvp_pgcache_rewind(struct vvp_seq_private *priv)
+{
+	if (priv->vsp_prev_pos) {
+		memset(&priv->vsp_id, 0, sizeof(priv->vsp_id));
+		priv->vsp_prev_pos = 0;
+		if (priv->vsp_clob) {
+			lu_object_ref_del(&priv->vsp_clob->co_lu, "dump",
+					  current);
+			cl_object_put(priv->vsp_env, priv->vsp_clob);
+		}
+		priv->vsp_clob = NULL;
+	}
+}
+
+static struct page *vvp_pgcache_next_page(struct vvp_seq_private *priv)
+{
+	priv->vsp_id.vpi_index += 1;
+	return vvp_pgcache_current(priv);
+}
+
 static void *vvp_pgcache_start(struct seq_file *f, loff_t *pos)
 {
 	struct vvp_seq_private *priv = f->private;
-	struct page *ret;
 
-	if (priv->vsp_sbi->ll_site->ls_obj_hash->hs_cur_bits >
-	    64 - PGC_OBJ_SHIFT)
-		ret = ERR_PTR(-EFBIG);
-	else
-		ret = vvp_pgcache_find(priv->vsp_env,
-				       &priv->vsp_sbi->ll_cl->cd_lu_dev,
-				       &priv->vsp_clob, pos);
+	if (*pos == 0) {
+		vvp_pgcache_rewind(priv);
+	} else if (*pos == priv->vsp_prev_pos) {
+		/* Return the current item */;
+	} else {
+		WARN_ON(*pos != priv->vsp_prev_pos + 1);
+		priv->vsp_id.vpi_index += 1;
+	}
 
-	return ret;
+	priv->vsp_prev_pos = *pos;
+	return vvp_pgcache_current(priv);
 }
 
 static void *vvp_pgcache_next(struct seq_file *f, void *v, loff_t *pos)
 {
 	struct vvp_seq_private *priv = f->private;
-	struct page *ret;
 
-	*pos += 1;
-	ret = vvp_pgcache_find(priv->vsp_env,
-			       &priv->vsp_sbi->ll_cl->cd_lu_dev,
-			       &priv->vsp_clob, pos);
-	return ret;
+	WARN_ON(*pos != priv->vsp_prev_pos);
+
+	priv->vsp_prev_pos = *pos;
+	return vvp_pgcache_next_page(priv);
 }
 
 static void vvp_pgcache_stop(struct seq_file *f, void *v)
@@ -615,6 +591,8 @@  static int vvp_dump_pgcache_seq_open(struct inode *inode, struct file *filp)
 
 	priv->vsp_sbi = inode->i_private;
 	priv->vsp_env = cl_env_get(&priv->vsp_refcheck);
+	priv->vsp_clob = NULL;
+	memset(&priv->vsp_id, 0, sizeof(priv->vsp_id));
 	if (IS_ERR(priv->vsp_env)) {
 		int err = PTR_ERR(priv->vsp_env);
 
@@ -629,6 +607,11 @@  static int vvp_dump_pgcache_seq_release(struct inode *inode, struct file *file)
 	struct seq_file *seq = file->private_data;
 	struct vvp_seq_private *priv = seq->private;
 
+	if (priv->vsp_clob) {
+		lu_object_ref_del(&priv->vsp_clob->co_lu, "dump", current);
+		cl_object_put(priv->vsp_env, priv->vsp_clob);
+	}
+
 	cl_env_put(priv->vsp_env, &priv->vsp_refcheck);
 	return seq_release_private(inode, file);
 }