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    SubjectRe: synchronous mounts
    "Stephen C. Tweedie" wrote:
    > Hi,
    > On Thu, Nov 15, 2001 at 12:03:57AM -0800, Andrew Morton wrote:
    > > Linux is not syncing write() data for files on synchronously mounted
    > > filesystems, and it isn't syncing write() data for ext2/3 files which
    > > are operating under `chattr +S'.
    > In the past, chattr +S and mount -o sync always resulted in sync
    > metadata with no guarantees about data.
    > I'm not sure this makes much sense, but it's what has always happened.
    > For directories, the behaviour is fine, in particular as it gives us
    > the same directory sync consistency semantics as synchronous BSD UFS.
    > It's not clear to me that chattr/mount sync options make _any_ sense
    > for regular file metadata. Rather than tightening up the semantics,
    > I'd actually prefer to restrict them so that they only apply to
    > directories. Users who set the sync bits are usually doing so for
    > applications like MTAs where it's directory syncing which is
    > what matters: the apps typically fsync the files themselves, anyway.

    OK, that makes sense. Thanks. The `mount' and `chattr' manpages
    need updating...

    So shall we try to nail this down? Synchronous mounts and chattr +S
    provide synchronous semantics for directory contents, diretory metadata
    and directory inodes only. And fsync() will write out a file's data,
    metadata and inode?

    If this is correct then there are a few places where ext2 is
    syncing stuff unnecessarily - file indirect blocks, etc. Not
    very important at this stage I guess.

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