Andy Isaacson <[EMAIL PROTECTED]> wrote: > > On Tue, Apr 06, 2004 at 05:33:26PM -0700, Andrew Morton wrote: > > Andy Isaacson <[EMAIL PROTECTED]> wrote: > > > dd(1) is convenient for this purpose, but is lacking a method > > > to force O_DIRECT. The enclosed patch adds a "conv=direct" flag to > > > enable this usage. > > > > This would be rather nice to have. You'll need to ensure that the data > > is page-aligned in memory. > > So, some confusion on my part about O_DIRECT: I can't get O_DIRECT to > work on ext3, at all, on 2.4.25
ext3 doesn't support O_DIRECT in 2.4 kernels. I did a patch once and I think it's in 2.4-aa kernels. ext3 supports O_DIRECT in 2.6 kernels. Quite a number of filesystems do. > -- open(O_DIRECT) succeeds, but the write > returns EINVAL. Yup that's a bit silly. In 2.6 we do the check at open() and fcntl() time. In 2.4 we don't fail until the actual I/O attempt. > Same code works fine when writing to a block device. > If the problem is that ext3 can't support O_DIRECT, why does the open > succeed? We have been insufficiently assiduous in merging externally-supported patches into the mainline 2.4 tree. > > While you're there, please add an fsync-before-closing option. > > Easy enough. How does this look? Note that C_TWOBUFS ensures the > output buffer is getpagesize()-aligned. Looks nice and simple. You'll need an ext2 filesystem to test it under 2.4. Be aware that it's rather a challenge to actually get the O_DIRECT #define in scope under some glibc versions. I think you need to define _GNU_SOURCE or something like that. _______________________________________________ Bug-coreutils mailing list [EMAIL PROTECTED] http://mail.gnu.org/mailman/listinfo/bug-coreutils
