Commit 5a2b4062 authored Oct 11, 2006 by Vasily Averin Committed by Linus Torvalds Oct 11, 2006

[PATCH] ext2: errors behaviour fix



Current error behaviour for ext2 and ext3 filesystems does not fully
correspond to the documentation and should be fixed.

According to man 8 mount, ext2 and ext3 file systems allow to set one of 3
different on-errors behaviours:

  ---- start of quote man 8 mount ----

  errors=continue / errors=remount-ro / errors=panic

    Define the behaviour when an error is encountered.  (Either ignore
    errors and just mark the file system erroneous and continue, or remount
    the file system read-only, or panic and halt the system.) The default is
    set in the filesystem superblock, and can be changed using tune2fs(8).

  ---- end of quote ----

However EXT3_ERRORS_CONTINUE is not read from the superblock, and thus
ERRORS_CONT is not saved on the sbi->s_mount_opt.  It leads to the incorrect
handle of errors on ext3.

Then we've checked corresponding code in ext2 and discovered that it is buggy
as well:

- EXT2_ERRORS_CONTINUE is not read from the superblock (the same);

- parse_option() does not clean the alternative values and thus something
  like (ERRORS_CONT|ERRORS_RO) can be set;

- if options are omitted, parse_option() does not set any of these options.

Therefore it is possible to set any combination of these options on the ext2:

- none of them may be set: EXT2_ERRORS_CONTINUE on superblock / empty mount
  options;

- any of them may be set using mount options;

- 2 any options may be set: by using EXT2_ERRORS_RO/EXT2_ERRORS_PANIC on the
  superblock and other value in mount options;

- and finally all three options may be set by adding third option in remount.

Currently ext2 uses these values only in ext2_error() and it is not leading to
any noticeable troubles.  However somebody may be discouraged when he will try
to workaround EXT2_ERRORS_PANIC on the superblock by using errors=continue in
mount options.

This patch:

EXT2_ERRORS_CONTINUE should be read from the superblock as default value for
error behaviour.  parse_option() should clean the alternative options and
should not change default value taken from the superblock.

Signed-off-by: Vasily Averin <vvs@sw.ru>
Acked-by: Kirill Korotaev <dev@openvz.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

parent 2245d7c2

fs/ext2/super.c

+11 −5

Original line number	Diff line number	Diff line
		@@ -364,7 +364,6 @@ static int parse_options (char * options,
		{
		char * p;
		substring_t args[MAX_OPT_ARGS];
		unsigned long kind = EXT2_MOUNT_ERRORS_CONT;
		int option;

		if (!options)
		@@ -404,13 +403,19 @@ static int parse_options (char * options,
		/* sb_block = match_int(&args[0]); /
		break;
		case Opt_err_panic:
		kind = EXT2_MOUNT_ERRORS_PANIC;
		clear_opt (sbi->s_mount_opt, ERRORS_CONT);
		clear_opt (sbi->s_mount_opt, ERRORS_RO);
		set_opt (sbi->s_mount_opt, ERRORS_PANIC);
		break;
		case Opt_err_ro:
		kind = EXT2_MOUNT_ERRORS_RO;
		clear_opt (sbi->s_mount_opt, ERRORS_CONT);
		clear_opt (sbi->s_mount_opt, ERRORS_PANIC);
		set_opt (sbi->s_mount_opt, ERRORS_RO);
		break;
		case Opt_err_cont:
		kind = EXT2_MOUNT_ERRORS_CONT;
		clear_opt (sbi->s_mount_opt, ERRORS_RO);
		clear_opt (sbi->s_mount_opt, ERRORS_PANIC);
		set_opt (sbi->s_mount_opt, ERRORS_CONT);
		break;
		case Opt_nouid32:
		set_opt (sbi->s_mount_opt, NO_UID32);
		@@ -489,7 +494,6 @@ static int parse_options (char * options,
		return 0;
		}
		}
		sbi->s_mount_opt \|= kind;
		return 1;
		}

		@@ -715,6 +719,8 @@ static int ext2_fill_super(struct super_block sb, void data, int silent)
		set_opt(sbi->s_mount_opt, ERRORS_PANIC);
		else if (le16_to_cpu(sbi->s_es->s_errors) == EXT2_ERRORS_RO)
		set_opt(sbi->s_mount_opt, ERRORS_RO);
		else
		set_opt(sbi->s_mount_opt, ERRORS_CONT);

		sbi->s_resuid = le16_to_cpu(es->s_def_resuid);
		sbi->s_resgid = le16_to_cpu(es->s_def_resgid);

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