On 12/18/12 2:14 AM, Michael Tokarev wrote: > Ping? Almost 2 months has passed since initial patch... > > Thanks, > > /mjt Michael, Lukas commented a while ago (10/25) that he was unable to reproduce the problem. Do you have any comment on that? TBH it's long enough ago that I've forgotten the issue ;) But Lukas' question may be what's holding Ted up. -Eric > On 25.10.2012 12:39, Michael Tokarev wrote: >> When a journal-less ext4 filesystem is mounted on a read-only block >> device (blockdev --setro will do), each remount (for other, unrelated, >> flags, like suid=>nosuid etc) results in a series of scary messages >> from kernel telling about I/O errors on the device. >> >> This is becauese of the following code ext4_remount(): >> >> if (sbi->s_journal == NULL) >> ext4_commit_super(sb, 1); >> >> at the end of remount procedure, which forces writing (flushing) of >> a superblock regardless whenever it is dirty or not, if the filesystem >> is readonly or not, and whenever the device itself is readonly or not. >> >> The proposed fix tests whenever both old mount flags and new mount >> flags does not include MS_READONLY, and only in this case calls >> ext4_commit_super(). >> >> Maybe it is sufficient to check for MS_READONLY just in old mount >> options (old_sb_flags). Note this is journal-less mode, so, for >> example, we weren't have journal replay operation, so if old flags >> include MS_REASONLY, we shuold have no dirty blocks at all, and >> there's no reason to call ext4_commit_super(). >> >> But only in case both old and new flags include MS_READONLY we're >> certain we will not write anything - if new flag does not include >> this bit, we will write sooner or later anyway, so preventing just >> one commit_super() at the _beginning_ of mount is not really necessary. >> >> This change probably applicable to -stable, -- not because it fixes >> a serious bug, but because the messages printed by the kernel are >> rather scary for an average user. On the other hand, actual usage >> of ext4 in nojournal mode on a read-only medium is very rare. >> >> Thanks to Eric Sandeen for help in diagnosing this issue. >> >> Signed-off-By: Michael Tokarev <mjt@xxxxxxxxxx> >> --- >> fs/ext4/super.c | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/fs/ext4/super.c b/fs/ext4/super.c >> index 3e0851e..2e896fd 100644 >> --- a/fs/ext4/super.c >> +++ b/fs/ext4/super.c >> @@ -4687,7 +4687,7 @@ static int ext4_remount(struct super_block *sb, int *flags, char *data) >> } >> >> ext4_setup_system_zone(sb); >> - if (sbi->s_journal == NULL) >> + if (sbi->s_journal == NULL && !(sb->s_flags & old_sb_flags & MS_RDONLY)) >> ext4_commit_super(sb, 1); >> >> unlock_super(sb); > -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
