Re: soft updates and qmail (RE: qmail IO problems)

[Matt Dillon]

:kirk said (but I have not completely checked it) that if you fsync a file,
:it will effectively fsync all the way back to the root of the filesystem.
:
:I don't know how true this is, but cerainly the inode is updated before 
:fsync returns. I cannot tell if any directory entries pointing at that file
:that have not yet been sync'd are forced out before it returns....
:
:      __--_|\  Julian Elischer
:     /       \ [EMAIL PROTECTED]

    This is totally 100% correct.  If you fsync() a file, softupdates
    will guarentee that not only is the file consistent, but that the
    appropriate portions of the directory the file is in will be consistent.
    If you crash right then, on boot/fsck the file will be found in the
    directory.

    A non-softupdates standard filesystem mount, whether it be normal,
    synchronous, or asynchronous, cannot make that guarentee.   Only
    Journaled filesystems (XFS, ReiserFS) can make similar guarentees.

                                                -Matt



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