[PATCH] disk quotas fail when /etc/mtab is symlinked to /proc/mounts

If /etc/mtab is a regular file all of the mount options (of a file system)
are written to /etc/mtab by the mount command. The quota tools look there
for the quota strings for their operation. If, however, /etc/mtab is a
symlink to /proc/mounts (a "good thing" in some environments) the tools
don't write anything - they assume the kernel will take care of things.

While the quota options are sent down to the kernel via the mount system
call and the file system codes handle them properly unfortunately there is
no code to echo the quota strings into /proc/mounts and the quota tools
fail in the symlink case.

The attached patchs modify the EXT[2|3] and JFS codes to add the necessary
hooks. The show_options function of each file system in these patches
currently deal with only those things that seemed related to quotas;
especially in the EXT3 case more can be done (later?).

Jan Kara also noted the difficulty in moving these changes above the FS
codes responding similarly to myself to Andrew's comment about possible
VFS migration. Issue summary:

- FS codes have to process the entire string of options anyway.

- Only FS codes that use quotas must have a show_options function (for
quotas to work properly) however quotas are only used in a small number
of FS.

- Since most of the quota using FS support other options these FS codes
should have the a show_options function to show those options - and the
quota echoing becomes virtually negligible.

Based on feedback I have modified my patches from the original:

JFS a missing patch has been restored to the posting
EXT[2|3] and JFS always use the show_options function
- Each FS has at least one FS specific option displayed
- QUOTA output is under a CONFIG_QUOTA ifdef
- a follow-on patch will add a multitude of options for each FS
EXT[2|3] and JFS "quota" is treated as "usrquota"
EXT3 journalled data check for journalled quota removed
EXT[2|3] mount when quota specified but not compiled in

- no changes from my original patch. I tested the patch and the codes
warn but

- still mount. With all due respection I believe the comments
otherwise were a

- misread of the patch. Please reread/test and comment. XFS patch
removed - the XFS team already made the necessary changes EXT3 mixing
old and new quotas are handled differently (not purely exclusive)

- if old and new quotas for the same type are used together the old
type is silently depricated for compatability (e.g. usrquota and
usrjquota)

- mixing of old and new quotas is an error (e.g. usrjquota and
grpquota)

Signed-off-by: Mark Bellon <[e-mail]>
Acked-by: Dave Kleikamp <[e-mail]>
Cc: Jan Kara <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

fs/ext2/super.c

···
 #include <linux/config.h>
 #include <linux/module.h>
 #include <linux/string.h>
+#include <linux/fs.h>
 #include <linux/slab.h>
 #include <linux/init.h>
 #include <linux/blkdev.h>
···
 #include <linux/buffer_head.h>
 #include <linux/smp_lock.h>
 #include <linux/vfs.h>
+#include <linux/seq_file.h>
+#include <linux/mount.h>
 #include <asm/uaccess.h>
 #include "ext2.h"
 #include "xattr.h"
···
 #endif
 }
 
+static int ext2_show_options(struct seq_file *seq, struct vfsmount *vfs)
+{
+	struct ext2_sb_info *sbi = EXT2_SB(vfs->mnt_sb);
+
+	if (sbi->s_mount_opt & EXT2_MOUNT_GRPID)
+		seq_puts(seq, ",grpid");
+	else
+		seq_puts(seq, ",nogrpid");
+
+#if defined(CONFIG_QUOTA)
+	if (sbi->s_mount_opt & EXT2_MOUNT_USRQUOTA)
+		seq_puts(seq, ",usrquota");
+
+	if (sbi->s_mount_opt & EXT2_MOUNT_GRPQUOTA)
+		seq_puts(seq, ",grpquota");
+#endif
+
+	return 0;
+}
+
 #ifdef CONFIG_QUOTA
 static ssize_t ext2_quota_read(struct super_block *sb, int type, char *data, size_t len, loff_t off);
 static ssize_t ext2_quota_write(struct super_block *sb, int type, const char *data, size_t len, loff_t off);
···
 	.statfs		= ext2_statfs,
 	.remount_fs	= ext2_remount,
 	.clear_inode	= ext2_clear_inode,
+	.show_options	= ext2_show_options,
 #ifdef CONFIG_QUOTA
 	.quota_read	= ext2_quota_read,
 	.quota_write	= ext2_quota_write,
···
 
 enum {
 	Opt_bsd_df, Opt_minix_df, Opt_grpid, Opt_nogrpid,
-	Opt_resgid, Opt_resuid, Opt_sb, Opt_err_cont, Opt_err_panic, Opt_err_ro,
-	Opt_nouid32, Opt_check, Opt_nocheck, Opt_debug, Opt_oldalloc, Opt_orlov, Opt_nobh,
-	Opt_user_xattr, Opt_nouser_xattr, Opt_acl, Opt_noacl, Opt_xip,
-	Opt_ignore, Opt_err,
+	Opt_resgid, Opt_resuid, Opt_sb, Opt_err_cont, Opt_err_panic,
+	Opt_err_ro, Opt_nouid32, Opt_check, Opt_nocheck, Opt_debug,
+	Opt_oldalloc, Opt_orlov, Opt_nobh, Opt_user_xattr, Opt_nouser_xattr,
+	Opt_acl, Opt_noacl, Opt_xip, Opt_ignore, Opt_err, Opt_quota,
+	Opt_usrquota, Opt_grpquota
 };
 
 static match_table_t tokens = {
···
 	{Opt_acl, "acl"},
 	{Opt_noacl, "noacl"},
 	{Opt_xip, "xip"},
-	{Opt_ignore, "grpquota"},
+	{Opt_grpquota, "grpquota"},
 	{Opt_ignore, "noquota"},
-	{Opt_ignore, "quota"},
-	{Opt_ignore, "usrquota"},
+	{Opt_quota, "quota"},
+	{Opt_usrquota, "usrquota"},
 	{Opt_err, NULL}
 };
 
···
 			printk("EXT2 xip option not supported\n");
 #endif
 			break;
+
+#if defined(CONFIG_QUOTA)
+		case Opt_quota:
+		case Opt_usrquota:
+			set_opt(sbi->s_mount_opt, USRQUOTA);
+			break;
+
+		case Opt_grpquota:
+			set_opt(sbi->s_mount_opt, GRPQUOTA);
+			break;
+#else
+		case Opt_quota:
+		case Opt_usrquota:
+		case Opt_grpquota:
+			printk(KERN_ERR
+				"EXT2-fs: quota operations not supported.\n");
+
+			break;
+#endif
+
 		case Opt_ignore:
 			break;
 		default:

fs/ext3/super.c

···
 #include <linux/mount.h>
 #include <linux/namei.h>
 #include <linux/quotaops.h>
+#include <linux/seq_file.h>
 #include <asm/uaccess.h>
 #include "xattr.h"
 #include "acl.h"
···
 	kfree(rsv);
 }
 
-#ifdef CONFIG_QUOTA
+static int ext3_show_options(struct seq_file *seq, struct vfsmount *vfs)
+{
+	struct ext3_sb_info *sbi = EXT3_SB(vfs->mnt_sb);
 
+	if (sbi->s_mount_opt & EXT3_MOUNT_JOURNAL_DATA)
+		seq_puts(seq, ",data=journal");
+
+	if (sbi->s_mount_opt & EXT3_MOUNT_ORDERED_DATA)
+		seq_puts(seq, ",data=ordered");
+
+	if (sbi->s_mount_opt & EXT3_MOUNT_WRITEBACK_DATA)
+		seq_puts(seq, ",data=writeback");
+
+#if defined(CONFIG_QUOTA)
+	if (sbi->s_jquota_fmt)
+		seq_printf(seq, ",jqfmt=%s",
+		(sbi->s_jquota_fmt == QFMT_VFS_OLD) ? "vfsold": "vfsv0");
+
+	if (sbi->s_qf_names[USRQUOTA])
+		seq_printf(seq, ",usrjquota=%s", sbi->s_qf_names[USRQUOTA]);
+
+	if (sbi->s_qf_names[GRPQUOTA])
+		seq_printf(seq, ",grpjquota=%s", sbi->s_qf_names[GRPQUOTA]);
+
+	if (sbi->s_mount_opt & EXT3_MOUNT_USRQUOTA)
+		seq_puts(seq, ",usrquota");
+
+	if (sbi->s_mount_opt & EXT3_MOUNT_GRPQUOTA)
+		seq_puts(seq, ",grpquota");
+#endif
+
+	return 0;
+}
+
+#ifdef CONFIG_QUOTA
 #define QTYPE2NAME(t) ((t)==USRQUOTA?"user":"group")
 #define QTYPE2MOPT(on, t) ((t)==USRQUOTA?((on)##USRJQUOTA):((on)##GRPJQUOTA))
 
···
 	.statfs		= ext3_statfs,
 	.remount_fs	= ext3_remount,
 	.clear_inode	= ext3_clear_inode,
+	.show_options	= ext3_show_options,
 #ifdef CONFIG_QUOTA
 	.quota_read	= ext3_quota_read,
 	.quota_write	= ext3_quota_write,
···
 	Opt_abort, Opt_data_journal, Opt_data_ordered, Opt_data_writeback,
 	Opt_usrjquota, Opt_grpjquota, Opt_offusrjquota, Opt_offgrpjquota,
 	Opt_jqfmt_vfsold, Opt_jqfmt_vfsv0, Opt_quota, Opt_noquota,
-	Opt_ignore, Opt_barrier, Opt_err, Opt_resize,
+	Opt_ignore, Opt_barrier, Opt_err, Opt_resize, Opt_usrquota,
+	Opt_grpquota
 };
 
 static match_table_t tokens = {
···
 	{Opt_grpjquota, "grpjquota=%s"},
 	{Opt_jqfmt_vfsold, "jqfmt=vfsold"},
 	{Opt_jqfmt_vfsv0, "jqfmt=vfsv0"},
-	{Opt_quota, "grpquota"},
+	{Opt_grpquota, "grpquota"},
 	{Opt_noquota, "noquota"},
 	{Opt_quota, "quota"},
-	{Opt_quota, "usrquota"},
+	{Opt_usrquota, "usrquota"},
 	{Opt_barrier, "barrier=%u"},
 	{Opt_err, NULL},
 	{Opt_resize, "resize"},
···
 			sbi->s_jquota_fmt = QFMT_VFS_V0;
 			break;
 		case Opt_quota:
+		case Opt_usrquota:
 			set_opt(sbi->s_mount_opt, QUOTA);
+			set_opt(sbi->s_mount_opt, USRQUOTA);
+			break;
+		case Opt_grpquota:
+			set_opt(sbi->s_mount_opt, QUOTA);
+			set_opt(sbi->s_mount_opt, GRPQUOTA);
 			break;
 		case Opt_noquota:
 			if (sb_any_quota_enabled(sb)) {
···
 				return 0;
 			}
 			clear_opt(sbi->s_mount_opt, QUOTA);
+			clear_opt(sbi->s_mount_opt, USRQUOTA);
+			clear_opt(sbi->s_mount_opt, GRPQUOTA);
 			break;
 #else
+		case Opt_quota:
+		case Opt_usrquota:
+		case Opt_grpquota:
 		case Opt_usrjquota:
 		case Opt_grpjquota:
 		case Opt_offusrjquota:
···
 				"EXT3-fs: journalled quota options not "
 				"supported.\n");
 			break;
-		case Opt_quota:
 		case Opt_noquota:
 			break;
 #endif
···
 		}
 	}
 #ifdef CONFIG_QUOTA
-	if (!sbi->s_jquota_fmt && (sbi->s_qf_names[USRQUOTA] ||
-	    sbi->s_qf_names[GRPQUOTA])) {
-		printk(KERN_ERR
-			"EXT3-fs: journalled quota format not specified.\n");
-		return 0;
+	if (sbi->s_qf_names[USRQUOTA] || sbi->s_qf_names[GRPQUOTA]) {
+		if ((sbi->s_mount_opt & EXT3_MOUNT_USRQUOTA) &&
+		     sbi->s_qf_names[USRQUOTA])
+			clear_opt(sbi->s_mount_opt, USRQUOTA);
+
+		if ((sbi->s_mount_opt & EXT3_MOUNT_GRPQUOTA) &&
+		     sbi->s_qf_names[GRPQUOTA])
+			clear_opt(sbi->s_mount_opt, GRPQUOTA);
+
+		if ((sbi->s_qf_names[USRQUOTA] &&
+				(sbi->s_mount_opt & EXT3_MOUNT_GRPQUOTA)) ||
+		    (sbi->s_qf_names[GRPQUOTA] &&
+				(sbi->s_mount_opt & EXT3_MOUNT_USRQUOTA))) {
+			printk(KERN_ERR "EXT3-fs: old and new quota "
+					"format mixing.\n");
+			return 0;
+		}
+
+		if (!sbi->s_jquota_fmt) {
+			printk(KERN_ERR "EXT3-fs: journalled quota format "
+					"not specified.\n");
+			return 0;
+		}
+	} else {
+		if (sbi->s_jquota_fmt) {
+			printk(KERN_ERR "EXT3-fs: journalled quota format "
+					"specified with no journalling "
+					"enabled.\n");
+			return 0;
+		}
 	}
 #endif
-
 	return 1;
 }
 

fs/jfs/jfs_filsys.h

···
 #define JFS_ERR_CONTINUE   0x00000004   /* continue */
 #define JFS_ERR_PANIC      0x00000008   /* panic */
 
+#define	JFS_USRQUOTA	0x00000010
+#define	JFS_GRPQUOTA	0x00000020
+
 /* platform option (conditional compilation) */
 #define JFS_AIX		0x80000000	/* AIX support */
 /*	POSIX name/directory  support */

fs/jfs/super.c

···
 #include <linux/parser.h>
 #include <linux/completion.h>
 #include <linux/vfs.h>
+#include <linux/mount.h>
 #include <linux/moduleparam.h>
 #include <linux/posix_acl.h>
 #include <asm/uaccess.h>
+#include <linux/seq_file.h>
 
 #include "jfs_incore.h"
 #include "jfs_filsys.h"
···
 
 enum {
 	Opt_integrity, Opt_nointegrity, Opt_iocharset, Opt_resize,
-	Opt_resize_nosize, Opt_errors, Opt_ignore, Opt_err,
+	Opt_resize_nosize, Opt_errors, Opt_ignore, Opt_err, Opt_quota,
+	Opt_usrquota, Opt_grpquota
 };
 
 static match_table_t tokens = {
···
 	{Opt_errors, "errors=%s"},
 	{Opt_ignore, "noquota"},
 	{Opt_ignore, "quota"},
-	{Opt_ignore, "usrquota"},
-	{Opt_ignore, "grpquota"},
+	{Opt_usrquota, "usrquota"},
+	{Opt_grpquota, "grpquota"},
 	{Opt_err, NULL}
 };
 
···
 			}
 			break;
 		}
+
+#if defined(CONFIG_QUOTA)
+		case Opt_quota:
+		case Opt_usrquota:
+			*flag |= JFS_USRQUOTA;
+			break;
+		case Opt_grpquota:
+			*flag |= JFS_GRPQUOTA;
+			break;
+#else
+		case Opt_usrquota:
+		case Opt_grpquota:
+		case Opt_quota:
+			printk(KERN_ERR
+			       "JFS: quota operations not supported\n");
+			break;
+#endif
+
 		default:
 			printk("jfs: Unrecognized mount option \"%s\" "
 					" or missing value\n", p);
···
 	return 0;
 }
 
+static int jfs_show_options(struct seq_file *seq, struct vfsmount *vfs)
+{
+	struct jfs_sb_info *sbi = JFS_SBI(vfs->mnt_sb);
+
+	if (sbi->flag & JFS_NOINTEGRITY)
+		seq_puts(seq, ",nointegrity");
+	else
+		seq_puts(seq, ",integrity");
+
+#if defined(CONFIG_QUOTA)
+	if (sbi->flag & JFS_USRQUOTA)
+		seq_puts(seq, ",usrquota");
+
+	if (sbi->flag & JFS_GRPQUOTA)
+		seq_puts(seq, ",grpquota");
+#endif
+
+	return 0;
+}
+
 static struct super_operations jfs_super_operations = {
 	.alloc_inode	= jfs_alloc_inode,
 	.destroy_inode	= jfs_destroy_inode,
···
 	.unlockfs       = jfs_unlockfs,
 	.statfs		= jfs_statfs,
 	.remount_fs	= jfs_remount,
+	.show_options	= jfs_show_options
 };
 
 static struct export_operations jfs_export_operations = {

include/linux/ext2_fs.h

···
 #define EXT2_MOUNT_XATTR_USER		0x004000  /* Extended user attributes */
 #define EXT2_MOUNT_POSIX_ACL		0x008000  /* POSIX Access Control Lists */
 #define EXT2_MOUNT_XIP			0x010000  /* Execute in place */
+#define EXT2_MOUNT_USRQUOTA		0x020000 /* user quota */
+#define EXT2_MOUNT_GRPQUOTA		0x040000 /* group quota */
+
 
 #define clear_opt(o, opt)		o &= ~EXT2_MOUNT_##opt
 #define set_opt(o, opt)			o |= EXT2_MOUNT_##opt

include/linux/ext3_fs.h

···
 #define EXT3_MOUNT_BARRIER		0x20000 /* Use block barriers */
 #define EXT3_MOUNT_NOBH			0x40000 /* No bufferheads */
 #define EXT3_MOUNT_QUOTA		0x80000 /* Some quota option set */
+#define EXT3_MOUNT_USRQUOTA		0x100000 /* "old" user quota */
+#define EXT3_MOUNT_GRPQUOTA		0x200000 /* "old" group quota */
 
 /* Compatibility, for having both ext2_fs.h and ext3_fs.h included at once */
 #ifndef _LINUX_EXT2_FS_H