On Mon, Jul 29, 2013 at 11:00 AM, majianpeng <majianpeng@xxxxxxxxx> wrote:
>
> [snip]
> >I don't think the later was_short can handle the hole case. For the hole case,
> >we should try reading next strip object instead of return. how about
> >below patch.
> >
> Hi Yan,
> i uesed this demo to test hole case.
> dd if=/dev/urandom bs=4096 count=2 of=file_with_holes
> dd if=/dev/urandom bs=4096 seek=7 count=2 of=file_with_holes
>
> dd if=file_with_holes of=/dev/null bs=16k count=1 iflag=direct
> Using the dynamic_debug in striped_read, the message are:
> >[ 8743.663499] ceph: file.c:350 : striped_read 0~16384 (read 0) got 16384
> >[ 8743.663502] ceph: file.c:390 : striped_read returns 16384
> From the messages, we can see it can't hit the short-read.
> For the ceph-file-hole, how does the ceph handle?
> Or am i missing something?
the default strip size is 4M, all data are written to the first object
in your test case.
could you try something like below.
dd if=/dev/urandom bs=1M count=2 of=file_with_holes
dd if=/dev/urandom bs=1M count=2 seek=4 of=file_with_holes conv=notrunc
dd if=file_with_holes bs=8M >/dev/null
Regards
Yan, Zheng
>
>
> Thanks!
> Jianpeng Ma
>
> >Regards
> >Yan, Zheng
> >---
> >diff --git a/fs/ceph/file.c b/fs/ceph/file.c
> >index 271a346..6ca2921 100644
> >--- a/fs/ceph/file.c
> >+++ b/fs/ceph/file.c
> >@@ -350,16 +350,17 @@ more:
> > ret, hit_stripe ? " HITSTRIPE" : "", was_short ? " SHORT" : "");
> >
> > if (ret > 0) {
> >- int didpages = (page_align + ret) >> PAGE_CACHE_SHIFT;
> >+ int didpages = (page_align + this_len) >> PAGE_CACHE_SHIFT;
> >
> >- if (read < pos - off) {
> >- dout(" zero gap %llu to %llu\n", off + read, pos);
> >- ceph_zero_page_vector_range(page_align + read,
> >- pos - off - read, pages);
> >+ if (was_short) {
> >+ dout(" zero gap %llu to %llu\n",
> >+ pos + ret, pos + this_len);
> >+ ceph_zero_page_vector_range(page_align + ret,
> >+ this_len - ret, page_pos);
> > }
> >- pos += ret;
> >+ pos += this_len;
> > read = pos - off;
> >- left -= ret;
> >+ left -= this_len;
> > page_pos += didpages;
> > pages_left -= didpages;
> >
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