* Tino Reichardt <list-linux-fsde...@mcmilk.de> wrote:
> This patch adds support for the two linux interfaces of the discard/TRIM
> command for SSD devices and sparse/thinly-provisioned LUNs.

Fixed a problem when setting minlen in jfs_ioc_trim().

Signed-off-by: Tino Reichardt <list-...@mcmilk.de>


-- 
regards, TR
diff -X exclude -urpN linux-git/Documentation/filesystems/jfs.txt 
linux_jfs-trim/Documentation/filesystems/jfs.txt
--- linux-git/Documentation/filesystems/jfs.txt 2011-03-01 10:22:59.000000000 
+0100
+++ linux_jfs-trim/Documentation/filesystems/jfs.txt    2012-07-26 
22:52:33.244721671 +0200
@@ -3,6 +3,7 @@ IBM's Journaled File System (JFS) for Li
 JFS Homepage:  http://jfs.sourceforge.net/
 
 The following mount options are supported:
+(*) == default
 
 iocharset=name Character set to use for converting from Unicode to
                ASCII.  The default is to do no conversion.  Use
@@ -21,12 +22,12 @@ nointegrity Do not write to the journal.
                from backup media.  The integrity of the volume is not
                guaranteed if the system abnormally abends.
 
-integrity      Default.  Commit metadata changes to the journal.  Use this
+integrity(*)   Default.  Commit metadata changes to the journal.  Use this
                option to remount a volume where the nointegrity option was
                previously specified in order to restore normal behavior.
 
 errors=continue                Keep going on a filesystem error.
-errors=remount-ro      Default. Remount the filesystem read-only on an error.
+errors=remount-ro(*)   Default. Remount the filesystem read-only on an error.
 errors=panic           Panic and halt the machine if an error occurs.
 
 uid=value      Override on-disk uid with specified value
@@ -35,6 +36,18 @@ umask=value  Override on-disk umask with
                directories, the execute bit will be set if the corresponding
                read bit is set.
 
+discard=minlen This enables/disables the use of discard/TRIM commands.
+discard                The discard/TRIM commands are sent to the underlying
+nodiscard(*)   block device when blocks are freed. This is useful for SSD
+               devices and sparse/thinly-provisioned LUNs.  The FITRIM ioctl
+               command is also available together with the nodiscard option.
+               The value of minlen specifies the minimum blockcount, when
+               a TRIM command to the block device is considered usefull.
+               When no value is given to the discard option, it defaults to
+               64 blocks, which means 256KiB in JFS.
+               The minlen value of discard overrides the minlen value given
+               on an FITRIM ioctl().
+
 Please send bugs, comments, cards and letters to sha...@linux.vnet.ibm.com.
 
 The JFS mailing list can be subscribed to by using the link labeled
diff -X exclude -urpN linux-git/fs/jfs/Makefile linux_jfs-trim/fs/jfs/Makefile
--- linux-git/fs/jfs/Makefile   2011-08-17 07:31:10.000000000 +0200
+++ linux_jfs-trim/fs/jfs/Makefile      2012-07-26 22:53:48.640979880 +0200
@@ -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 -X exclude -urpN linux-git/fs/jfs/ioctl.c linux_jfs-trim/fs/jfs/ioctl.c
--- linux-git/fs/jfs/ioctl.c    2012-01-10 19:31:59.000000000 +0100
+++ linux_jfs-trim/fs/jfs/ioctl.c       2012-07-26 22:53:48.640979880 +0200
@@ -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((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,
        case JFS_IOC_SETFLAGS32:
                cmd = JFS_IOC_SETFLAGS;
                break;
+       case FITRIM:
+               cmd = FITRIM;
+               break;
        }
        return jfs_ioctl(filp, cmd, arg);
 }
diff -X exclude -urpN linux-git/fs/jfs/jfs_discard.c 
linux_jfs-trim/fs/jfs/jfs_discard.c
--- linux-git/fs/jfs/jfs_discard.c      1970-01-01 01:00:00.000000000 +0100
+++ linux_jfs-trim/fs/jfs/jfs_discard.c 2012-07-26 22:53:48.640979880 +0200
@@ -0,0 +1,119 @@
+/*
+ *   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_dmap.h"
+#include "jfs_lock.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)) {
+               printk(KERN_ERR "JFS: sb_issue_discard"
+                       "(%p, %llu, %llu, GFP_NOFS, 0) = %d => failure!\n", sb,
+                       (unsigned long long)blkno,
+                       (unsigned long long)nblocks, r);
+       }
+
+#ifdef JFS_DEBUG_TRIM
+       printk(KERN_INFO "JFS: sb_issue_discard"
+               "(%p, %llu, %llu, GFP_NOFS, 0) = %d\n", sb,
+               (unsigned long long)blkno,
+               (unsigned long long)nblocks, r);
+#endif
+
+       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 -X exclude -urpN linux-git/fs/jfs/jfs_discard.h 
linux_jfs-trim/fs/jfs/jfs_discard.h
--- linux-git/fs/jfs/jfs_discard.h      1970-01-01 01:00:00.000000000 +0100
+++ linux_jfs-trim/fs/jfs/jfs_discard.h 2012-07-26 22:53:48.640979880 +0200
@@ -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 -X exclude -urpN linux-git/fs/jfs/jfs_dmap.c 
linux_jfs-trim/fs/jfs/jfs_dmap.c
--- linux-git/fs/jfs/jfs_dmap.c 2011-08-17 07:31:10.000000000 +0200
+++ linux_jfs-trim/fs/jfs/jfs_dmap.c    2012-07-26 22:53:48.644313195 +0200
@@ -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,
 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 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 +351,15 @@ int dbFree(struct inode *ip, s64 blkno,
                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 +1104,6 @@ static int dbExtend(struct inode *ip, s6
                /* we were not successful */
                release_metapage(mp);
 
-
        return (rc);
 }
 
@@ -1590,6 +1598,117 @@ static int dbAllocAny(struct bmap * bmp,
 
 
 /*
+ * NAME:       dbDiscardAG()
+ *
+ * FUNCTION:   attempt to discard (TRIM) all free blocks of specific AG
+ *
+ *             algorithm:
+ *             1) allocate blocks, as large as possible and save them
+ *             2) trim all these saved block/length values
+ *             3) mark the blocks free again
+ *
+ *             benefit:
+ *             - we work only on one ag at some time, which is fully blocked
+ *             - 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 = 32 * 1024;
+
+       /* prevent others from writing new stuff here, while trimming */
+       IWRITE_LOCK(ipbmap, RDWRLOCK_DMAP);
+
+       /* worst value: each free block gets an entry */
+       nblocks = bmp->db_agfree[agno];
+       totrim = kmalloc(sizeof(struct range2trim) * range_cnt, GFP_NOFS);
+       if (totrim == NULL) {
+               jfs_error(bmp->db_ipbmap->i_sb,
+                         "dbDiscardAG: no space for trim array");
+               IWRITE_UNLOCK(ipbmap);
+               return 0;
+       }
+
+       tt = totrim;
+       while (nblocks >= minlen) {
+               l2nb = BLKSTOL2(nblocks);
+
+               /* 0 = okay, -EIO = fatal, -ENOSPC -> block kleiner */
+               rc = dbAllocAG(bmp, agno, nblocks, l2nb, &blkno);
+               if (rc == 0) {
+                       tt->blkno = blkno;
+                       tt->nblocks = nblocks;
+                       tt++; count++;
+
+#ifdef JFS_DEBUG_TRIM
+               printk(KERN_INFO "JFS: agno=%d/%d, blkno:%ld, nblocks=%ld\n",
+                       agno+1, bmp->db_numag, (long int)blkno,
+                       (long int)nblocks);
+#endif
+
+                       /* 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 */
+                       printk(KERN_ERR "JFS: dbDiscardAG: -EIO\n");
+                       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++) {
+               if (!(JFS_SBI(sb)->flag & JFS_DISCARD)) {
+                       /* not needed, when online discard is used */
+                       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 -X exclude -urpN linux-git/fs/jfs/jfs_dmap.h 
linux_jfs-trim/fs/jfs/jfs_dmap.h
--- linux-git/fs/jfs/jfs_dmap.h 2011-08-17 07:31:10.000000000 +0200
+++ linux_jfs-trim/fs/jfs/jfs_dmap.h    2012-07-26 22:53:48.644313195 +0200
@@ -311,4 +311,6 @@ extern int dbAllocBottomUp(struct inode
 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 -X exclude -urpN linux-git/fs/jfs/jfs_filsys.h 
linux_jfs-trim/fs/jfs/jfs_filsys.h
--- linux-git/fs/jfs/jfs_filsys.h       2011-08-17 07:31:10.000000000 +0200
+++ linux_jfs-trim/fs/jfs/jfs_filsys.h  2012-07-26 22:53:48.644313195 +0200
@@ -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 -X exclude -urpN linux-git/fs/jfs/jfs_incore.h 
linux_jfs-trim/fs/jfs/jfs_incore.h
--- linux-git/fs/jfs/jfs_incore.h       2011-08-17 07:31:10.000000000 +0200
+++ linux_jfs-trim/fs/jfs/jfs_incore.h  2012-07-26 22:53:48.647646510 +0200
@@ -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 -X exclude -urpN linux-git/fs/jfs/super.c linux_jfs-trim/fs/jfs/super.c
--- linux-git/fs/jfs/super.c    2012-07-24 21:31:28.000000000 +0200
+++ linux_jfs-trim/fs/jfs/super.c       2012-07-26 23:00:28.018816264 +0200
@@ -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"
@@ -197,7 +198,8 @@ static void jfs_put_super(struct super_b
 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}
 };
 
@@ -324,12 +329,14 @@ static int parse_options(char *options,
                        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;
@@ -341,6 +348,43 @@ static int parse_options(char *options,
                        }
                        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 {
+                               printk(KERN_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 {
+                               printk(KERN_ERR "JFS: discard option "
+                                       "not supported on device\n");
+                       }
+                       break;
+               }
+
                default:
                        printk("jfs: Unrecognized mount option \"%s\" "
                                        " or missing value\n", p);
@@ -625,6 +669,8 @@ static int jfs_show_options(struct seq_f
                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)

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