I can't think of any valid reason for ext3 to not use barriers when they are available; I believe this is necessary for filesystem integrity in the face of a volatile write cache on storage. An administrator who trusts that the cache is sufficiently battery- backed (and power supplies are sufficiently redundant, etc...) can always turn it back off again. SuSE has carried such a patch for quite some time now. Also document the mount option while we're at it. Signed-off-by: Eric Sandeen <sandeen@xxxxxxxxxx> Acked-by: Jan Kara <jack@xxxxxxx> --- Documentation/filesystems/ext3.txt | 12 ++++++++++-- fs/ext3/super.c | 11 +++++++++-- 2 files changed, 19 insertions(+), 4 deletions(-) diff --git a/Documentation/filesystems/ext3.txt b/Documentation/filesystems/ext3.txt index b45f3c1..daab1f5 100644 --- a/Documentation/filesystems/ext3.txt +++ b/Documentation/filesystems/ext3.txt @@ -52,8 +52,16 @@ commit=nrsec (*) Ext3 can be told to sync all its data and metadata Setting it to very large values will improve performance. -barrier=1 This enables/disables barriers. barrier=0 disables - it, barrier=1 enables it. +barrier=<0|1(*)> This enables/disables the use of write barriers in + the jbd code. barrier=0 disables, barrier=1 enables. + This also requires an IO stack which can support + barriers, and if jbd gets an error on a barrier + write, it will disable again with a warning. + Write barriers enforce proper on-disk ordering + of journal commits, making volatile disk write caches + safe to use, at some performance penalty. If + your disks are battery-backed in one way or another, + disabling barriers may safely improve performance. orlov (*) This enables the new Orlov block allocator. It is enabled by default. diff --git a/fs/ext3/super.c b/fs/ext3/super.c index fe3119a..9c30dc7 100644 --- a/fs/ext3/super.c +++ b/fs/ext3/super.c @@ -555,6 +555,7 @@ static int ext3_show_options(struct seq_file *seq, struct vfsmount *vfs) struct super_block *sb = vfs->mnt_sb; struct ext3_sb_info *sbi = EXT3_SB(sb); struct ext3_super_block *es = sbi->s_es; + journal_t *journal = sbi->s_journal; unsigned long def_mount_opts; def_mount_opts = le32_to_cpu(es->s_default_mount_opts); @@ -613,8 +614,13 @@ static int ext3_show_options(struct seq_file *seq, struct vfsmount *vfs) seq_printf(seq, ",commit=%u", (unsigned) (sbi->s_commit_interval / HZ)); } - if (test_opt(sb, BARRIER)) - seq_puts(seq, ",barrier=1"); + /* + * jbd inherits the barrier flag from ext3, and may actually + * turn off barriers if a write fails, so it's the real test. + */ + if (!test_opt(sb, BARRIER) || + (journal && !(journal->j_flags & JFS_BARRIER))) + seq_puts(seq, ",barrier=0"); if (test_opt(sb, NOBH)) seq_puts(seq, ",nobh"); @@ -1589,6 +1595,7 @@ static int ext3_fill_super (struct super_block *sb, void *data, int silent) sbi->s_resgid = le16_to_cpu(es->s_def_resgid); set_opt(sbi->s_mount_opt, RESERVATION); + set_opt(sbi->s_mount_opt, BARRIER); if (!parse_options ((char *) data, sb, &journal_inum, &journal_devnum, NULL, 0)) -- 1.5.3.6 -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
