FAT: add 'errors' mount option

On severe errors FAT remounts itself in read-only mode. Allow to
specify FAT fs desired behavior through 'errors' mount option:
panic, continue or remount read-only.

`mount -t [fat|vfat] -o errors=[panic,remount-ro,continue] \
	<bdev> <mount point>`

This is analog to ext2 fs 'errors' mount option.

Signed-off-by: Denis Karpov <ext-denis.2.karpov@nokia.com>
Signed-off-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index 296785a..2b90522 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -76,7 +76,7 @@
 		return 0;
 
 	if (iblock != MSDOS_I(inode)->mmu_private >> sb->s_blocksize_bits) {
-		fat_fs_panic(sb, "corrupted file size (i_pos %lld, %lld)",
+		fat_fs_error(sb, "corrupted file size (i_pos %lld, %lld)",
 			MSDOS_I(inode)->i_pos, MSDOS_I(inode)->mmu_private);
 		return -EIO;
 	}
@@ -834,6 +834,12 @@
 		seq_puts(m, ",flush");
 	if (opts->tz_utc)
 		seq_puts(m, ",tz=UTC");
+	if (opts->errors == FAT_ERRORS_CONT)
+		seq_puts(m, ",errors=continue");
+	else if (opts->errors == FAT_ERRORS_PANIC)
+		seq_puts(m, ",errors=panic");
+	else
+		seq_puts(m, ",errors=remount-ro");
 
 	return 0;
 }
@@ -846,7 +852,8 @@
 	Opt_charset, Opt_shortname_lower, Opt_shortname_win95,
 	Opt_shortname_winnt, Opt_shortname_mixed, Opt_utf8_no, Opt_utf8_yes,
 	Opt_uni_xl_no, Opt_uni_xl_yes, Opt_nonumtail_no, Opt_nonumtail_yes,
-	Opt_obsolate, Opt_flush, Opt_tz_utc, Opt_rodir, Opt_err,
+	Opt_obsolate, Opt_flush, Opt_tz_utc, Opt_rodir, Opt_err_cont,
+	Opt_err_panic, Opt_err_ro, Opt_err,
 };
 
 static const match_table_t fat_tokens = {
@@ -869,6 +876,11 @@
 	{Opt_showexec, "showexec"},
 	{Opt_debug, "debug"},
 	{Opt_immutable, "sys_immutable"},
+	{Opt_flush, "flush"},
+	{Opt_tz_utc, "tz=UTC"},
+	{Opt_err_cont, "errors=continue"},
+	{Opt_err_panic, "errors=panic"},
+	{Opt_err_ro, "errors=remount-ro"},
 	{Opt_obsolate, "conv=binary"},
 	{Opt_obsolate, "conv=text"},
 	{Opt_obsolate, "conv=auto"},
@@ -880,8 +892,6 @@
 	{Opt_obsolate, "cvf_format=%20s"},
 	{Opt_obsolate, "cvf_options=%100s"},
 	{Opt_obsolate, "posix"},
-	{Opt_flush, "flush"},
-	{Opt_tz_utc, "tz=UTC"},
 	{Opt_err, NULL},
 };
 static const match_table_t msdos_tokens = {
@@ -951,6 +961,7 @@
 	opts->numtail = 1;
 	opts->usefree = opts->nocase = 0;
 	opts->tz_utc = 0;
+	opts->errors = FAT_ERRORS_RO;
 	*debug = 0;
 
 	if (!options)
@@ -1043,6 +1054,15 @@
 		case Opt_tz_utc:
 			opts->tz_utc = 1;
 			break;
+		case Opt_err_cont:
+			opts->errors = FAT_ERRORS_CONT;
+			break;
+		case Opt_err_panic:
+			opts->errors = FAT_ERRORS_PANIC;
+			break;
+		case Opt_err_ro:
+			opts->errors = FAT_ERRORS_RO;
+			break;
 
 		/* msdos specific */
 		case Opt_dots: