Messages in this thread Patch in this message |  | | | Subject | Re: [Ext2-devel] Re: [PATCH 2/3] ext3 reservation allow turn off for specifed file | | From | Mingming Cao <> | | Date | 25 Oct 2004 13:33:05 -0700 |
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On Wed, 2004-10-20 at 10:55, Ray Lee wrote: > On Mon, 2004-10-18 at 18:01 -0700, Mingming Cao wrote: > > On Mon, 2004-10-18 at 16:42, Andrew Morton wrote: > > > Applications currently pass a seeky-access hint into the kernel via > > > posix_fadvise(POSIX_FADV_RANDOM). It would be nice to hook into that > > [...] > > > Just thought seeky random write application could use the existing ioctl > > to let the kernel know it does not need reservation at all. Isn't that > > more straightforward? > > Going the ioctl route seems to imply that userspace would have to do a > posix_fadvise() call and the ioctl, as opposed to just the fadvise. No? > I'm betting the fadvise call is a little more portable as well.
Agreed. How about this: add a check in ext3_prepare_write(), if user passed seeky-access hint through posix_fadvise(via check for file->f_ra.ra_pages == 0), if so, close the reservation window. But we still need previous patch to handle window size 0(no reservation) in reservation code.
Currently the readahead is turned off if the userspace passed a seeky access hint to kernel by POSIX_FADVISE. It would be nice to turn off the block allocation reservation as well for seeky random write.
--- linux-2.6.9-rc4-mm1-ming/fs/ext3/inode.c | 9 +++++++++ 1 files changed, 9 insertions(+) diff -puN fs/ext3/inode.c~ext3_turn_off_reservation_by_fadvise fs/ext3/inode.c --- linux-2.6.9-rc4-mm1/fs/ext3/inode.c~ext3_turn_off_reservation_by_fadvise 2004-10-25 18:25:44.135751800 -0700 +++ linux-2.6.9-rc4-mm1-ming/fs/ext3/inode.c 2004-10-25 18:34:39.501363856 -0700 @@ -1008,6 +1008,15 @@ retry: ret = PTR_ERR(handle); goto out; } + + /* + * if user passed a seeky-access hint to kernel, + * through POSIX_FADV_RANDOM,(file->r_ra.ra_pages is cleared) + * turn off reservation for block allocation correspondingly. + */ + if (!file->f_ra.ra_pages) + atomic_set(&EXT3_I(inode)->i_rsv_window.rsv_goal_size, 0); + ret = block_prepare_write(page, from, to, ext3_get_block); if (ret) goto prepare_write_failed; _
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