fs/jfs: TRIM support for JFS Filesystem

This patch adds support for the two linux interfaces of the discard/TRIM
command for SSD devices and sparse/thinly-provisioned LUNs.

JFS will support batched discard via FITRIM ioctl and online discard
with the discard mount option.

Signed-off-by: Tino Reichardt <list-jfs@mcmilk.de>
Signed-off-by: Dave Kleikamp <dave.kleikamp@oracle.com>

9 files changed, 369 insertions, 21 deletions

diff --git a/fs/jfs/Makefile b/fs/jfs/Makefile
index a58fa72..d20d473 100644
--- a/fs/jfs/Makefile
+++ b/fs/jfs/Makefile
@@ -6,7 +6,7 @@ obj-$(CONFIG_JFS_FS) += jfs.o
 
 jfs-y    := super.o file.o inode.o namei.o jfs_mount.o jfs_umount.o \
 	    jfs_xtree.o jfs_imap.o jfs_debug.o jfs_dmap.o \
-	    jfs_unicode.o jfs_dtree.o jfs_inode.o \
+	    jfs_unicode.o jfs_dtree.o jfs_inode.o jfs_discard.o \
 	    jfs_extent.o symlink.o jfs_metapage.o \
 	    jfs_logmgr.o jfs_txnmgr.o jfs_uniupr.o \
 	    resize.o xattr.o ioctl.o
diff --git a/fs/jfs/ioctl.c b/fs/jfs/ioctl.c
index f19d1e0..bc555ff 100644
--- a/fs/jfs/ioctl.c
+++ b/fs/jfs/ioctl.c
@@ -11,13 +11,17 @@
 #include <linux/mount.h>
 #include <linux/time.h>
 #include <linux/sched.h>
+#include <linux/blkdev.h>
 #include <asm/current.h>
 #include <asm/uaccess.h>
 
+#include "jfs_filsys.h"
+#include "jfs_debug.h"
 #include "jfs_incore.h"
 #include "jfs_dinode.h"
 #include "jfs_inode.h"
-
+#include "jfs_dmap.h"
+#include "jfs_discard.h"
 
 static struct {
 	long jfs_flag;
@@ -123,6 +127,40 @@ setflags_out:
 		mnt_drop_write_file(filp);
 		return err;
 	}
+
+	case FITRIM:
+	{
+		struct super_block *sb = inode->i_sb;
+		struct request_queue *q = bdev_get_queue(sb->s_bdev);
+		struct fstrim_range range;
+		s64 ret = 0;
+
+		if (!capable(CAP_SYS_ADMIN))
+			return -EPERM;
+
+		if (!blk_queue_discard(q)) {
+			jfs_warn("FITRIM not supported on device");
+			return -EOPNOTSUPP;
+		}
+
+		if (copy_from_user(&range, (struct fstrim_range __user *)arg,
+		    sizeof(range)))
+			return -EFAULT;
+
+		range.minlen = max_t(unsigned int, range.minlen,
+			q->limits.discard_granularity);
+
+		ret = jfs_ioc_trim(inode, &range);
+		if (ret < 0)
+			return ret;
+
+		if (copy_to_user((struct fstrim_range __user *)arg, &range,
+		    sizeof(range)))
+			return -EFAULT;
+
+		return 0;
+	}
+
 	default:
 		return -ENOTTY;
 	}
@@ -142,6 +180,9 @@ long jfs_compat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 	case JFS_IOC_SETFLAGS32:
 		cmd = JFS_IOC_SETFLAGS;
 		break;
+	case FITRIM:
+		cmd = FITRIM;
+		break;
 	}
 	return jfs_ioctl(filp, cmd, arg);
 }
diff --git a/fs/jfs/jfs_discard.c b/fs/jfs/jfs_discard.c
new file mode 100644
index 0000000..9947563
--- /dev/null
+++ b/fs/jfs/jfs_discard.c
@@ -0,0 +1,117 @@
+/*
+ *   Copyright (C) Tino Reichardt, 2012
+ *
+ *   This program is free software;  you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation; either version 2 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY;  without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
+ *   the GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program;  if not, write to the Free Software
+ *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#include <linux/fs.h>
+#include <linux/slab.h>
+#include <linux/blkdev.h>
+
+#include "jfs_incore.h"
+#include "jfs_superblock.h"
+#include "jfs_discard.h"
+#include "jfs_dmap.h"
+#include "jfs_debug.h"
+
+
+/*
+ * NAME:	jfs_issue_discard()
+ *
+ * FUNCTION:	TRIM the specified block range on device, if supported
+ *
+ * PARAMETERS:
+ *	ip	- pointer to in-core inode
+ *	blkno	- starting block number to be trimmed (0..N)
+ *	nblocks	- number of blocks to be trimmed
+ *
+ * RETURN VALUES:
+ *	none
+ *
+ * serialization: IREAD_LOCK(ipbmap) held on entry/exit;
+ */
+void jfs_issue_discard(struct inode *ip, u64 blkno, u64 nblocks)
+{
+	struct super_block *sb = ip->i_sb;
+	int r = 0;
+
+	r = sb_issue_discard(sb, blkno, nblocks, GFP_NOFS, 0);
+	if (unlikely(r != 0)) {
+		jfs_err("JFS: sb_issue_discard" \
+			"(%p, %llu, %llu, GFP_NOFS, 0) = %d => failed!\n",
+			sb, (unsigned long long)blkno,
+			(unsigned long long)nblocks, r);
+	}
+
+	jfs_info("JFS: sb_issue_discard" \
+		"(%p, %llu, %llu, GFP_NOFS, 0) = %d\n",
+		sb, (unsigned long long)blkno,
+		(unsigned long long)nblocks, r);
+
+	return;
+}
+
+/*
+ * NAME:	jfs_ioc_trim()
+ *
+ * FUNCTION:	attempt to discard (TRIM) all free blocks from the
+ *              filesystem.
+ *
+ * PARAMETERS:
+ *	ip	- pointer to in-core inode;
+ *	range	- the range, given by user space
+ *
+ * RETURN VALUES:
+ *	0	- success
+ *	-EIO	- i/o error
+ */
+int jfs_ioc_trim(struct inode *ip, struct fstrim_range *range)
+{
+	struct inode *ipbmap = JFS_SBI(ip->i_sb)->ipbmap;
+	struct bmap *bmp = JFS_SBI(ip->i_sb)->bmap;
+	struct super_block *sb = ipbmap->i_sb;
+	int agno, agno_end;
+	s64 start, end, minlen;
+	u64 trimmed = 0;
+
+	/**
+	 * convert byte values to block size of filesystem:
+	 * start:	First Byte to trim
+	 * len:		number of Bytes to trim from start
+	 * minlen:	minimum extent length in Bytes
+	 */
+	start = range->start >> sb->s_blocksize_bits;
+	if (start < 0)
+		start = 0;
+	end = start + (range->len >> sb->s_blocksize_bits) - 1;
+	if (end >= bmp->db_mapsize)
+		end = bmp->db_mapsize - 1;
+	minlen = range->minlen >> sb->s_blocksize_bits;
+	if (minlen <= 0)
+		minlen = 1;
+
+	/**
+	 * we trim all ag's within the range
+	 */
+	agno = BLKTOAG(start, JFS_SBI(ip->i_sb));
+	agno_end = BLKTOAG(end, JFS_SBI(ip->i_sb));
+	while (agno <= agno_end) {
+		trimmed += dbDiscardAG(ip, agno, minlen);
+		agno++;
+	}
+	range->len = trimmed << sb->s_blocksize_bits;
+
+	return 0;
+}
diff --git a/fs/jfs/jfs_discard.h b/fs/jfs/jfs_discard.h
new file mode 100644
index 0000000..40d1ee6
--- /dev/null
+++ b/fs/jfs/jfs_discard.h
@@ -0,0 +1,26 @@
+/*
+ *   Copyright (C) Tino Reichardt, 2012
+ *
+ *   This program is free software;  you can redistribute it and/or modify
+ *   it under the terms of the GNU General Public License as published by
+ *   the Free Software Foundation; either version 2 of the License, or
+ *   (at your option) any later version.
+ *
+ *   This program is distributed in the hope that it will be useful,
+ *   but WITHOUT ANY WARRANTY;  without even the implied warranty of
+ *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See
+ *   the GNU General Public License for more details.
+ *
+ *   You should have received a copy of the GNU General Public License
+ *   along with this program;  if not, write to the Free Software
+ *   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+#ifndef _H_JFS_DISCARD
+#define _H_JFS_DISCARD
+
+struct fstrim_range;
+
+extern void jfs_issue_discard(struct inode *ip, u64 blkno, u64 nblocks);
+extern int jfs_ioc_trim(struct inode *ip, struct fstrim_range *range);
+
+#endif /* _H_JFS_DISCARD */
diff --git a/fs/jfs/jfs_dmap.c b/fs/jfs/jfs_dmap.c
index 9cbd11a..174feb6 100644
--- a/fs/jfs/jfs_dmap.c
+++ b/fs/jfs/jfs_dmap.c
@@ -1,5 +1,6 @@
 /*
  *   Copyright (C) International Business Machines Corp., 2000-2004
+ *   Portions Copyright (C) Tino Reichardt, 2012
  *
  *   This program is free software;  you can redistribute it and/or modify
  *   it under the terms of the GNU General Public License as published by
@@ -25,6 +26,7 @@
 #include "jfs_lock.h"
 #include "jfs_metapage.h"
 #include "jfs_debug.h"
+#include "jfs_discard.h"
 
 /*
  *	SERIALIZATION of the Block Allocation Map.
@@ -104,7 +106,6 @@ static int dbFreeBits(struct bmap * bmp, struct dmap * dp, s64 blkno,
 static int dbFreeDmap(struct bmap * bmp, struct dmap * dp, s64 blkno,
 		      int nblocks);
 static int dbMaxBud(u8 * cp);
-s64 dbMapFileSizeToMapSize(struct inode *ipbmap);
 static int blkstol2(s64 nb);
 
 static int cntlz(u32 value);
@@ -145,7 +146,6 @@ static const s8 budtab[256] = {
 	2, 1, 1, 1, 1, 0, 0, 0, 1, 0, 0, 0, 1, 0, 0, -1
 };
 
-
 /*
  * NAME:	dbMount()
  *
@@ -310,7 +310,6 @@ int dbSync(struct inode *ipbmap)
 	return (0);
 }
 
-
 /*
  * NAME:	dbFree()
  *
@@ -337,6 +336,7 @@ int dbFree(struct inode *ip, s64 blkno, s64 nblocks)
 	s64 lblkno, rem;
 	struct inode *ipbmap = JFS_SBI(ip->i_sb)->ipbmap;
 	struct bmap *bmp = JFS_SBI(ip->i_sb)->bmap;
+	struct super_block *sb = ipbmap->i_sb;
 
 	IREAD_LOCK(ipbmap, RDWRLOCK_DMAP);
 
@@ -351,6 +351,13 @@ int dbFree(struct inode *ip, s64 blkno, s64 nblocks)
 		return -EIO;
 	}
 
+	/**
+	 * TRIM the blocks, when mounted with discard option
+	 */
+	if (JFS_SBI(sb)->flag & JFS_DISCARD)
+		if (JFS_SBI(sb)->minblks_trim <= nblocks)
+			jfs_issue_discard(ipbmap, blkno, nblocks);
+
 	/*
 	 * free the blocks a dmap at a time.
 	 */
@@ -1095,7 +1102,6 @@ static int dbExtend(struct inode *ip, s64 blkno, s64 nblocks, s64 addnblocks)
 		/* we were not successful */
 		release_metapage(mp);
 
-
 	return (rc);
 }
 
@@ -1590,6 +1596,117 @@ static int dbAllocAny(struct bmap * bmp, s64 nblocks, int l2nb, s64 * results)
 
 
 /*
+ * NAME:	dbDiscardAG()
+ *
+ * FUNCTION:	attempt to discard (TRIM) all free blocks of specific AG
+ *
+ *		algorithm:
+ *		1) allocate blocks, as large as possible and save them
+ *		   while holding IWRITE_LOCK on ipbmap
+ *		2) trim all these saved block/length values
+ *		3) mark the blocks free again
+ *
+ *		benefit:
+ *		- we work only on one ag at some time, minimizing how long we
+ *		  need to lock ipbmap
+ *		- reading / writing the fs is possible most time, even on
+ *		  trimming
+ *
+ *		downside:
+ *		- we write two times to the dmapctl and dmap pages
+ *		- but for me, this seems the best way, better ideas?
+ *		/TR 2012
+ *
+ * PARAMETERS:
+ *	ip	- pointer to in-core inode
+ *	agno	- ag to trim
+ *	minlen	- minimum value of contiguous blocks
+ *
+ * RETURN VALUES:
+ *	s64	- actual number of blocks trimmed
+ */
+s64 dbDiscardAG(struct inode *ip, int agno, s64 minlen)
+{
+	struct inode *ipbmap = JFS_SBI(ip->i_sb)->ipbmap;
+	struct bmap *bmp = JFS_SBI(ip->i_sb)->bmap;
+	s64 nblocks, blkno;
+	u64 trimmed = 0;
+	int rc, l2nb;
+	struct super_block *sb = ipbmap->i_sb;
+
+	struct range2trim {
+		u64 blkno;
+		u64 nblocks;
+	} *totrim, *tt;
+
+	/* max blkno / nblocks pairs to trim */
+	int count = 0, range_cnt;
+
+	/* prevent others from writing new stuff here, while trimming */
+	IWRITE_LOCK(ipbmap, RDWRLOCK_DMAP);
+
+	nblocks = bmp->db_agfree[agno];
+	range_cnt = nblocks;
+	do_div(range_cnt, (int)minlen);
+	range_cnt = min(range_cnt + 1, 32 * 1024);
+	totrim = kmalloc(sizeof(struct range2trim) * range_cnt, GFP_NOFS);
+	if (totrim == NULL) {
+		jfs_error(bmp->db_ipbmap->i_sb,
+			  "dbDiscardAG: no memory for trim array");
+		IWRITE_UNLOCK(ipbmap);
+		return 0;
+	}
+
+	tt = totrim;
+	while (nblocks >= minlen) {
+		l2nb = BLKSTOL2(nblocks);
+
+		/* 0 = okay, -EIO = fatal, -ENOSPC -> try smaller block */
+		rc = dbAllocAG(bmp, agno, nblocks, l2nb, &blkno);
+		if (rc == 0) {
+			tt->blkno = blkno;
+			tt->nblocks = nblocks;
+			tt++; count++;
+
+			/* the whole ag is free, trim now */
+			if (bmp->db_agfree[agno] == 0)
+				break;
+
+			/* give a hint for the next while */
+			nblocks = bmp->db_agfree[agno];
+			continue;
+		} else if (rc == -ENOSPC) {
+			/* search for next smaller log2 block */
+			l2nb = BLKSTOL2(nblocks) - 1;
+			nblocks = 1 << l2nb;
+		} else {
+			/* Trim any already allocated blocks */
+			jfs_error(bmp->db_ipbmap->i_sb,
+				"dbDiscardAG: -EIO");
+			break;
+		}
+
+		/* check, if our trim array is full */
+		if (unlikely(count >= range_cnt - 1))
+			break;
+	}
+	IWRITE_UNLOCK(ipbmap);
+
+	tt->nblocks = 0; /* mark the current end */
+	for (tt = totrim; tt->nblocks != 0; tt++) {
+		/* when mounted with online discard, dbFree() will
+		 * call jfs_issue_discard() itself */
+		if (!(JFS_SBI(sb)->flag & JFS_DISCARD))
+			jfs_issue_discard(ip, tt->blkno, tt->nblocks);
+		dbFree(ip, tt->blkno, tt->nblocks);
+		trimmed += tt->nblocks;
+	}
+	kfree(totrim);
+
+	return trimmed;
+}
+
+/*
  * NAME:	dbFindCtl()
  *
  * FUNCTION:	starting at a specified dmap control page level and block
diff --git a/fs/jfs/jfs_dmap.h b/fs/jfs/jfs_dmap.h
index 6dcb906..562b9a7e 100644
--- a/fs/jfs/jfs_dmap.h
+++ b/fs/jfs/jfs_dmap.h
@@ -311,4 +311,6 @@ extern int dbAllocBottomUp(struct inode *ip, s64 blkno, s64 nblocks);
 extern int dbExtendFS(struct inode *ipbmap, s64 blkno, s64 nblocks);
 extern void dbFinalizeBmap(struct inode *ipbmap);
 extern s64 dbMapFileSizeToMapSize(struct inode *ipbmap);
+extern s64 dbDiscardAG(struct inode *ip, int agno, s64 minlen);
+
 #endif				/* _H_JFS_DMAP */
diff --git a/fs/jfs/jfs_filsys.h b/fs/jfs/jfs_filsys.h
index b3f5463..b67d646 100644
--- a/fs/jfs/jfs_filsys.h
+++ b/fs/jfs/jfs_filsys.h
@@ -45,6 +45,9 @@
 /* mount time flag to disable journaling to disk */
 #define JFS_NOINTEGRITY 0x00000040
 
+/* mount time flag to enable TRIM to ssd disks */
+#define JFS_DISCARD     0x00000080
+
 /* commit option */
 #define	JFS_COMMIT	0x00000f00	/* commit option mask */
 #define	JFS_GROUPCOMMIT	0x00000100	/* group (of 1) commit */
diff --git a/fs/jfs/jfs_incore.h b/fs/jfs/jfs_incore.h
index 584a4a1..4fa958a 100644
--- a/fs/jfs/jfs_incore.h
+++ b/fs/jfs/jfs_incore.h
@@ -195,6 +195,7 @@ struct jfs_sb_info {
 	uint		uid;		/* uid to override on-disk uid */
 	uint		gid;		/* gid to override on-disk gid */
 	uint		umask;		/* umask to override on-disk umask */
+	uint		minblks_trim;	/* minimum blocks, for online trim */
 };
 
 /* jfs_sb_info commit_state */
diff --git a/fs/jfs/super.c b/fs/jfs/super.c
index c55c745..6f4ac1c 100644
--- a/fs/jfs/super.c
+++ b/fs/jfs/super.c
@@ -33,6 +33,7 @@
 #include <linux/slab.h>
 #include <asm/uaccess.h>
 #include <linux/seq_file.h>
+#include <linux/blkdev.h>
 
 #include "jfs_incore.h"
 #include "jfs_filsys.h"
@@ -100,7 +101,7 @@ void jfs_error(struct super_block *sb, const char * function, ...)
 	vsnprintf(error_buf, sizeof(error_buf), function, args);
 	va_end(args);
 
-	printk(KERN_ERR "ERROR: (device %s): %s\n", sb->s_id, error_buf);
+	pr_err("ERROR: (device %s): %s\n", sb->s_id, error_buf);
 
 	jfs_handle_error(sb);
 }
@@ -197,7 +198,8 @@ static void jfs_put_super(struct super_block *sb)
 enum {
 	Opt_integrity, Opt_nointegrity, Opt_iocharset, Opt_resize,
 	Opt_resize_nosize, Opt_errors, Opt_ignore, Opt_err, Opt_quota,
-	Opt_usrquota, Opt_grpquota, Opt_uid, Opt_gid, Opt_umask
+	Opt_usrquota, Opt_grpquota, Opt_uid, Opt_gid, Opt_umask,
+	Opt_discard, Opt_nodiscard, Opt_discard_minblk
 };
 
 static const match_table_t tokens = {
@@ -214,6 +216,9 @@ static const match_table_t tokens = {
 	{Opt_uid, "uid=%u"},
 	{Opt_gid, "gid=%u"},
 	{Opt_umask, "umask=%u"},
+	{Opt_discard, "discard"},
+	{Opt_nodiscard, "nodiscard"},
+	{Opt_discard_minblk, "discard=%u"},
 	{Opt_err, NULL}
 };
 
@@ -255,8 +260,7 @@ static int parse_options(char *options, struct super_block *sb, s64 *newLVSize,
 			else {
 				nls_map = load_nls(args[0].from);
 				if (!nls_map) {
-					printk(KERN_ERR
-					       "JFS: charset not found\n");
+					pr_err("JFS: charset not found\n");
 					goto cleanup;
 				}
 			}
@@ -272,8 +276,7 @@ static int parse_options(char *options, struct super_block *sb, s64 *newLVSize,
 			*newLVSize = sb->s_bdev->bd_inode->i_size >>
 				sb->s_blocksize_bits;
 			if (*newLVSize == 0)
-				printk(KERN_ERR
-				       "JFS: Cannot determine volume size\n");
+				pr_err("JFS: Cannot determine volume size\n");
 			break;
 		}
 		case Opt_errors:
@@ -294,8 +297,7 @@ static int parse_options(char *options, struct super_block *sb, s64 *newLVSize,
 				*flag &= ~JFS_ERR_REMOUNT_RO;
 				*flag |= JFS_ERR_PANIC;
 			} else {
-				printk(KERN_ERR
-				       "JFS: %s is an invalid error handler\n",
+				pr_err("JFS: %s is an invalid error handler\n",
 				       errors);
 				goto cleanup;
 			}
@@ -314,8 +316,7 @@ static int parse_options(char *options, struct super_block *sb, s64 *newLVSize,
 		case Opt_usrquota:
 		case Opt_grpquota:
 		case Opt_quota:
-			printk(KERN_ERR
-			       "JFS: quota operations not supported\n");
+			pr_err("JFS: quota operations not supported\n");
 			break;
 #endif
 		case Opt_uid:
@@ -324,23 +325,61 @@ static int parse_options(char *options, struct super_block *sb, s64 *newLVSize,
 			sbi->uid = simple_strtoul(uid, &uid, 0);
 			break;
 		}
+
 		case Opt_gid:
 		{
 			char *gid = args[0].from;
 			sbi->gid = simple_strtoul(gid, &gid, 0);
 			break;
 		}
+
 		case Opt_umask:
 		{
 			char *umask = args[0].from;
 			sbi->umask = simple_strtoul(umask, &umask, 8);
 			if (sbi->umask & ~0777) {
-				printk(KERN_ERR
-				       "JFS: Invalid value of umask\n");
+				pr_err("JFS: Invalid value of umask\n");
 				goto cleanup;
 			}
 			break;
 		}
+
+		case Opt_discard:
+		{
+			struct request_queue *q = bdev_get_queue(sb->s_bdev);
+			/* if set to 1, even copying files will cause
+			 * trimming :O
+			 * -> user has more control over the online trimming
+			 */
+			sbi->minblks_trim = 64;
+			if (blk_queue_discard(q)) {
+				*flag |= JFS_DISCARD;
+			} else {
+				pr_err("JFS: discard option " \
+					"not supported on device\n");
+			}
+			break;
+		}
+
+		case Opt_nodiscard:
+			*flag &= ~JFS_DISCARD;
+			break;
+
+		case Opt_discard_minblk:
+		{
+			struct request_queue *q = bdev_get_queue(sb->s_bdev);
+			char *minblks_trim = args[0].from;
+			if (blk_queue_discard(q)) {
+				*flag |= JFS_DISCARD;
+				sbi->minblks_trim = simple_strtoull(
+					minblks_trim, &minblks_trim, 0);
+			} else {
+				pr_err("JFS: discard option " \
+					"not supported on device\n");
+			}
+			break;
+		}
+
 		default:
 			printk("jfs: Unrecognized mount option \"%s\" "
 					" or missing value\n", p);
@@ -374,8 +413,8 @@ static int jfs_remount(struct super_block *sb, int *flags, char *data)
 
 	if (newLVSize) {
 		if (sb->s_flags & MS_RDONLY) {
-			printk(KERN_ERR
-		  "JFS: resize requires volume to be mounted read-write\n");
+			pr_err("JFS: resize requires volume" \
+				" to be mounted read-write\n");
 			return -EROFS;
 		}
 		rc = jfs_extendfs(sb, newLVSize, 0);
@@ -457,7 +496,7 @@ static int jfs_fill_super(struct super_block *sb, void *data, int silent)
 #endif
 
 	if (newLVSize) {
-		printk(KERN_ERR "resize option for remount only\n");
+		pr_err("resize option for remount only\n");
 		goto out_kfree;
 	}
 
@@ -625,6 +664,8 @@ static int jfs_show_options(struct seq_file *seq, struct dentry *root)
 		seq_printf(seq, ",umask=%03o", sbi->umask);
 	if (sbi->flag & JFS_NOINTEGRITY)
 		seq_puts(seq, ",nointegrity");
+	if (sbi->flag & JFS_DISCARD)
+		seq_printf(seq, ",discard=%u", sbi->minblks_trim);
 	if (sbi->nls_tab)
 		seq_printf(seq, ",iocharset=%s", sbi->nls_tab->charset);
 	if (sbi->flag & JFS_ERR_CONTINUE)