On 14:36 Срд 13 Июн , Hugh Dickins wrote: > On Wed, 13 Jun 2007, Dmitriy Monakhov wrote: > > > loop.c code itself is not perfect. In fact before Nick's patch > > partial write was't possible. Assumption what write chunks are > > always page aligned is realy weird ( see "index++" line). > > > > Signed-off-by: Dmitriy Monakhov <dmonakhov@xxxxxxxxxx> > > I'm interested, because I'm trying to chase down an -mm bug which > occasionally leaves me with 1k of zeroes where it shouldn't (in a > 1k bsize ext2 looped over tmpfs). The length of time for this to > happen varies a lot, so bisection has been misleading: maybe the > problem lies in Nick's patches, maybe it does not. > > But I don't understand your fix below at all. _If_ you need to > change the handling of index, then you need to change the handling > of offset too, don't you? > > But what's wrong with how inded was handled anyway? Yes, it might > be being incremented at the bottom of the loop when we haven't > reached the end of this page, but in that case we're not going > round the loop again anyway: len will now be 0. So no problem. > > One of us is missing something: please enlighten me - thanks. Yepp. You absolutely right, wrong patch was attached :( Btw: Nick's patches broke LO_CRYPT_XOR mode, but it is ok because this feature was absolete and not used by anyone, am i right here? > > Hugh > > > > > diff --git a/drivers/block/loop.c b/drivers/block/loop.c > > index 4bab9b1..8726da5 100644 > > --- a/drivers/block/loop.c > > +++ b/drivers/block/loop.c > > @@ -215,7 +215,6 @@ static int do_lo_send_aops(struct loop_device *lo, struct bio_vec *bvec, > > int len, ret; > > > > mutex_lock(&mapping->host->i_mutex); > > - index = pos >> PAGE_CACHE_SHIFT; > > offset = pos & ((pgoff_t)PAGE_CACHE_SIZE - 1); > > bv_offs = bvec->bv_offset; > > len = bvec->bv_len; > > @@ -226,6 +225,7 @@ static int do_lo_send_aops(struct loop_device *lo, struct bio_vec *bvec, > > struct page *page; > > void *fsdata; > > > > + index = pos >> PAGE_CACHE_SHIFT; > > IV = ((sector_t)index << (PAGE_CACHE_SHIFT - 9))+(offset >> 9); > > size = PAGE_CACHE_SIZE - offset; > > if (size > len) > > @@ -255,7 +255,6 @@ static int do_lo_send_aops(struct loop_device *lo, struct bio_vec *bvec, > > bv_offs += copied; > > len -= copied; > > offset = 0; > > - index++; > > pos += copied; > > } > > ret = 0; > - > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@xxxxxxxxxxxxxxx > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ - To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
