staging: lustre: linkea: linkEA size limitation

Under DNE mode, if we do not restrict the linkEA size, and if there
are too many cross-MDTs hard links to the same object, then it will
cause the llog overflow. On the other hand, too many linkEA entries
in the linkEA will serious affect the linkEA performance because we
only support to locate linkEA entry consecutively.

So we need to restrict the linkEA size. Currently, it is 4096 bytes,
that is independent from the backend. If too many hard links caused
the linkEA overflowed, we will add overflow timestamp in the linkEA
header.
Signed-off-by: Fan Yong <fan.yong@intel.com>
Intel-bug-id: https://jira.hpdd.intel.com/browse/LU-8569
Reviewed-on: https://review.whamcloud.com/23500Reviewed-by: Andreas Dilger <andreas.dilger@intel.com>
Reviewed-by: wangdi <di.wang@intel.com>
Reviewed-by: Lai Siyao <lai.siyao@intel.com>
Reviewed-by: Oleg Drokin <oleg.drokin@intel.com>
Signed-off-by: James Simmons <jsimmons@infradead.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/lustre/lustre/include/lustre/lustre_idl.h

@@ -3217,9 +3217,8 @@ struct link_ea_header {
 	__u32 leh_magic;
 	__u32 leh_reccount;
 	__u64 leh_len;      /* total size */
-	/* future use */
-	__u32 padding1;
-	__u32 padding2;
+	__u32 leh_overflow_time;
+	__u32 leh_padding;
 };
 
 /** Hardlink data is name and parent fid.

drivers/staging/lustre/lustre/include/lustre_linkea.h

@@ -26,7 +26,19 @@
  * Author: di wang <di.wang@intel.com>
  */
 
-#define DEFAULT_LINKEA_SIZE	4096
+/* There are several reasons to restrict the linkEA size:
+ *
+ * 1. Under DNE mode, if we do not restrict the linkEA size, and if there
+ *    are too many cross-MDTs hard links to the same object, then it will
+ *    casue the llog overflow.
+ *
+ * 2. Some backend has limited size for EA. For example, if without large
+ *    EA enabled, the ldiskfs will make all EAs to share one (4K) EA block.
+ *
+ * 3. Too many entries in linkEA will seriously affect linkEA performance
+ *    because we only support to locate linkEA entry consecutively.
+ */
+#define MAX_LINKEA_SIZE		4096
 
 struct linkea_data {
 	/**
@@ -43,6 +55,7 @@ struct linkea_data {
 
 int linkea_data_new(struct linkea_data *ldata, struct lu_buf *buf);
 int linkea_init(struct linkea_data *ldata);
+int linkea_init_with_rec(struct linkea_data *ldata);
 void linkea_entry_unpack(const struct link_ea_entry *lee, int *reclen,
 			 struct lu_name *lname, struct lu_fid *pfid);
 int linkea_entry_pack(struct link_ea_entry *lee, const struct lu_name *lname,

drivers/staging/lustre/lustre/llite/llite_lib.c

@@ -2540,7 +2540,7 @@ static int ll_linkea_decode(struct linkea_data *ldata, unsigned int linkno,
 	unsigned int idx;
 	int rc;
 
-	rc = linkea_init(ldata);
+	rc = linkea_init_with_rec(ldata);
 	if (rc < 0)
 		return rc;
 

drivers/staging/lustre/lustre/obdclass/linkea.c

@@ -39,6 +39,8 @@ int linkea_data_new(struct linkea_data *ldata, struct lu_buf *buf)
 	ldata->ld_leh->leh_magic = LINK_EA_MAGIC;
 	ldata->ld_leh->leh_len = sizeof(struct link_ea_header);
 	ldata->ld_leh->leh_reccount = 0;
+	ldata->ld_leh->leh_overflow_time = 0;
+	ldata->ld_leh->leh_padding = 0;
 	return 0;
 }
 EXPORT_SYMBOL(linkea_data_new);
@@ -53,11 +55,15 @@ int linkea_init(struct linkea_data *ldata)
 		leh->leh_magic = LINK_EA_MAGIC;
 		leh->leh_reccount = __swab32(leh->leh_reccount);
 		leh->leh_len = __swab64(leh->leh_len);
-		/* entries are swabbed by linkea_entry_unpack */
+		leh->leh_overflow_time = __swab32(leh->leh_overflow_time);
+		leh->leh_padding = __swab32(leh->leh_padding);
+		/* individual entries are swabbed by linkea_entry_unpack() */
 	}
+
 	if (leh->leh_magic != LINK_EA_MAGIC)
 		return -EINVAL;
-	if (leh->leh_reccount == 0)
+
+	if (leh->leh_reccount == 0 && leh->leh_overflow_time == 0)
 		return -ENODATA;
 
 	ldata->ld_leh = leh;
@@ -65,6 +71,18 @@ int linkea_init(struct linkea_data *ldata)
 }
 EXPORT_SYMBOL(linkea_init);
 
+int linkea_init_with_rec(struct linkea_data *ldata)
+{
+	int rc;
+
+	rc = linkea_init(ldata);
+	if (!rc && ldata->ld_leh->leh_reccount == 0)
+		rc = -ENODATA;
+
+	return rc;
+}
+EXPORT_SYMBOL(linkea_init_with_rec);
+
 /**
  * Pack a link_ea_entry.
  * All elements are stored as chars to avoid alignment issues.
@@ -94,6 +112,8 @@ EXPORT_SYMBOL(linkea_entry_pack);
 void linkea_entry_unpack(const struct link_ea_entry *lee, int *reclen,
 			 struct lu_name *lname, struct lu_fid *pfid)
 {
+	LASSERT(lee);
+
 	*reclen = (lee->lee_reclen[0] << 8) | lee->lee_reclen[1];
 	memcpy(pfid, &lee->lee_parent_fid, sizeof(*pfid));
 	fid_be_to_cpu(pfid, pfid);
@@ -110,25 +130,44 @@ EXPORT_SYMBOL(linkea_entry_unpack);
 int linkea_add_buf(struct linkea_data *ldata, const struct lu_name *lname,
 		   const struct lu_fid *pfid)
 {
-	LASSERT(ldata->ld_leh);
+	struct link_ea_header *leh = ldata->ld_leh;
+	int reclen;
+
+	LASSERT(leh);
 
 	if (!lname || !pfid)
 		return -EINVAL;
 
-	ldata->ld_reclen = lname->ln_namelen + sizeof(struct link_ea_entry);
-	if (ldata->ld_leh->leh_len + ldata->ld_reclen >
-	    ldata->ld_buf->lb_len) {
+	reclen = lname->ln_namelen + sizeof(struct link_ea_entry);
+	if (unlikely(leh->leh_len + reclen > MAX_LINKEA_SIZE)) {
+		/*
+		 * Use 32-bits to save the overflow time, although it will
+		 * shrink the ktime_get_real_seconds() returned 64-bits value
+		 * to 32-bits value, it is still quite large and can be used
+		 * for about 140 years. That is enough.
+		 */
+		leh->leh_overflow_time = ktime_get_real_seconds();
+		if (unlikely(leh->leh_overflow_time == 0))
+			leh->leh_overflow_time++;
+
+		CDEBUG(D_INODE, "No enough space to hold linkea entry '" DFID ": %.*s' at %u\n",
+		       PFID(pfid), lname->ln_namelen,
+		       lname->ln_name, leh->leh_overflow_time);
+		return 0;
+	}
+
+	if (leh->leh_len + reclen > ldata->ld_buf->lb_len) {
 		if (lu_buf_check_and_grow(ldata->ld_buf,
-					  ldata->ld_leh->leh_len +
-					  ldata->ld_reclen) < 0)
+					  leh->leh_len + reclen) < 0)
 			return -ENOMEM;
+
+		leh = ldata->ld_leh = ldata->ld_buf->lb_buf;
 	}
 
-	ldata->ld_leh = ldata->ld_buf->lb_buf;
-	ldata->ld_lee = ldata->ld_buf->lb_buf + ldata->ld_leh->leh_len;
+	ldata->ld_lee = ldata->ld_buf->lb_buf + leh->leh_len;
 	ldata->ld_reclen = linkea_entry_pack(ldata->ld_lee, lname, pfid);
-	ldata->ld_leh->leh_len += ldata->ld_reclen;
-	ldata->ld_leh->leh_reccount++;
+	leh->leh_len += ldata->ld_reclen;
+	leh->leh_reccount++;
 	CDEBUG(D_INODE, "New link_ea name '" DFID ":%.*s' is added\n",
 	       PFID(pfid), lname->ln_namelen, lname->ln_name);
 	return 0;
@@ -139,6 +178,7 @@ EXPORT_SYMBOL(linkea_add_buf);
 void linkea_del_buf(struct linkea_data *ldata, const struct lu_name *lname)
 {
 	LASSERT(ldata->ld_leh && ldata->ld_lee);
+	LASSERT(ldata->ld_leh->leh_reccount > 0);
 
 	ldata->ld_leh->leh_reccount--;
 	ldata->ld_leh->leh_len -= ldata->ld_reclen;
@@ -174,7 +214,8 @@ int linkea_links_find(struct linkea_data *ldata, const struct lu_name *lname,
 
 	LASSERT(ldata->ld_leh);
 
-	/* link #0 */
+	/* link #0, if leh_reccount == 0 we skip the loop and return -ENOENT */
+	if (likely(ldata->ld_leh->leh_reccount > 0))
 		ldata->ld_lee = (struct link_ea_entry *)(ldata->ld_leh + 1);
 
 	for (count = 0; count < ldata->ld_leh->leh_reccount; count++) {

drivers/staging/lustre/lustre/ptlrpc/wiretest.c

@@ -3820,14 +3820,14 @@ void lustre_assert_wire_constants(void)
 		 (long long)(int)offsetof(struct link_ea_header, leh_len));
 	LASSERTF((int)sizeof(((struct link_ea_header *)0)->leh_len) == 8, "found %lld\n",
 		 (long long)(int)sizeof(((struct link_ea_header *)0)->leh_len));
-	LASSERTF((int)offsetof(struct link_ea_header, padding1) == 16, "found %lld\n",
-		 (long long)(int)offsetof(struct link_ea_header, padding1));
-	LASSERTF((int)sizeof(((struct link_ea_header *)0)->padding1) == 4, "found %lld\n",
-		 (long long)(int)sizeof(((struct link_ea_header *)0)->padding1));
-	LASSERTF((int)offsetof(struct link_ea_header, padding2) == 20, "found %lld\n",
-		 (long long)(int)offsetof(struct link_ea_header, padding2));
-	LASSERTF((int)sizeof(((struct link_ea_header *)0)->padding2) == 4, "found %lld\n",
-		 (long long)(int)sizeof(((struct link_ea_header *)0)->padding2));
+	LASSERTF((int)offsetof(struct link_ea_header, leh_overflow_time) == 16, "found %lld\n",
+		 (long long)(int)offsetof(struct link_ea_header, leh_overflow_time));
+	LASSERTF((int)sizeof(((struct link_ea_header *)0)->leh_overflow_time) == 4, "found %lld\n",
+		 (long long)(int)sizeof(((struct link_ea_header *)0)->leh_overflow_time));
+	LASSERTF((int)offsetof(struct link_ea_header, leh_padding) == 20, "found %lld\n",
+		 (long long)(int)offsetof(struct link_ea_header, leh_padding));
+	LASSERTF((int)sizeof(((struct link_ea_header *)0)->leh_padding) == 4, "found %lld\n",
+		 (long long)(int)sizeof(((struct link_ea_header *)0)->leh_padding));
 	BUILD_BUG_ON(LINK_EA_MAGIC != 0x11EAF1DFUL);
 
 	/* Checks for struct link_ea_entry */