Date: Sat, 12 Oct 2002 16:30:22 -0700 (PDT) From: Peter Godman <pete@isilon.com> To: freebsd-fs@freebsd.org Subject: ufs_update and waitfor flag Message-ID: <Pine.BSF.4.21.0210121624030.66567-100000@isilon.com>
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An application running on my system is doing basically:
fd = open(file)
read(fd, ...)
fsync(fd)
close(fd)
My root filesystem is mounted sync,noatime, but this sequence of
operations still results in a bwrite during fsync in ufs_update. This
seems to be the result of the following code in ufs_update:
int
ffs_update(vp, waitfor)
struct vnode *vp;
int waitfor;
{
struct fs *fs;
struct buf *bp;
struct inode *ip;
int error;
ufs_itimes(vp);
ip = VTOI(vp);
/* vvvvvvvvvvvv ?? */
if ((ip->i_flag & IN_MODIFIED) == 0 && waitfor == 0)
return (0);
ip->i_flag &= ~(IN_LAZYMOD | IN_MODIFIED);
...
The relevant part here is the "waitfor == 0" in the bailout check. Though
the flags on the inode do not indicate that the inode is modified, the
fact that we wish to wait for the operation to complete results a write
happening here that otherwise wouldn't have. Do other people read this
code the same way? Is this desired or expected behaviour? What would
happen if I commented out the check for waitfor == 0 at this
point? Anyone know why this check is there? Most likely I will modify
the application in question, but would like to know whether this code
should change too.
Thanks!
Peter Godman
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