| Message ID | 20240213093713.1753368-3-kernel@pankajraghav.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | enable bs > ps in XFS | expand |
On 2/13/24 10:37, Pankaj Raghav (Samsung) wrote: > From: Luis Chamberlain <mcgrof@kernel.org> > > Supporting mapping_min_order implies that we guarantee each folio in the > page cache has at least an order of mapping_min_order. So when adding new > folios to the page cache we must ensure the index used is aligned to the > mapping_min_order as the page cache requires the index to be aligned to > the order of the folio. > > A higher order folio than min_order by definition is a multiple of the > min_order. If an index is aligned to an order higher than a min_order, it > will also be aligned to the min order. > > This effectively introduces no new functional changes when min order is > not set other than a few rounding computations that should result in the > same value. > > Signed-off-by: Luis Chamberlain <mcgrof@kernel.org> > Signed-off-by: Pankaj Raghav <p.raghav@samsung.com> > --- > mm/filemap.c | 34 ++++++++++++++++++++++++++-------- > 1 file changed, 26 insertions(+), 8 deletions(-) > > diff --git a/mm/filemap.c b/mm/filemap.c > index 750e779c23db..323a8e169581 100644 > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -2479,14 +2479,16 @@ static int filemap_get_pages(struct kiocb *iocb, size_t count, > { > struct file *filp = iocb->ki_filp; > struct address_space *mapping = filp->f_mapping; > + unsigned int min_nrpages = mapping_min_folio_nrpages(mapping); > struct file_ra_state *ra = &filp->f_ra; > - pgoff_t index = iocb->ki_pos >> PAGE_SHIFT; > + pgoff_t index = round_down(iocb->ki_pos >> PAGE_SHIFT, min_nrpages); > pgoff_t last_index; > struct folio *folio; > int err = 0; > > /* "last_index" is the index of the page beyond the end of the read */ > last_index = DIV_ROUND_UP(iocb->ki_pos + count, PAGE_SIZE); > + last_index = round_up(last_index, min_nrpages); Huh? 'last_index' is unset here; sure you mean 'iocb->ki_pos + count' ? And what's the rationale to replace 'DIV_ROUND_UP' with 'round_up' ? > retry: > if (fatal_signal_pending(current)) > return -EINTR; > @@ -2502,8 +2504,7 @@ static int filemap_get_pages(struct kiocb *iocb, size_t count, > if (!folio_batch_count(fbatch)) { > if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_WAITQ)) > return -EAGAIN; > - err = filemap_create_folio(filp, mapping, > - iocb->ki_pos >> PAGE_SHIFT, fbatch); > + err = filemap_create_folio(filp, mapping, index, fbatch); > if (err == AOP_TRUNCATED_PAGE) > goto retry; > return err; > @@ -3095,7 +3096,10 @@ static struct file *do_sync_mmap_readahead(struct vm_fault *vmf) > struct file *file = vmf->vma->vm_file; > struct file_ra_state *ra = &file->f_ra; > struct address_space *mapping = file->f_mapping; > - DEFINE_READAHEAD(ractl, file, ra, mapping, vmf->pgoff); > + unsigned int min_order = mapping_min_folio_order(mapping); > + unsigned int min_nrpages = mapping_min_folio_nrpages(file->f_mapping); > + pgoff_t index = round_down(vmf->pgoff, min_nrpages); > + DEFINE_READAHEAD(ractl, file, ra, mapping, index); > struct file *fpin = NULL; > unsigned long vm_flags = vmf->vma->vm_flags; > unsigned int mmap_miss; > @@ -3147,10 +3151,11 @@ static struct file *do_sync_mmap_readahead(struct vm_fault *vmf) > */ > fpin = maybe_unlock_mmap_for_io(vmf, fpin); > ra->start = max_t(long, 0, vmf->pgoff - ra->ra_pages / 2); > + ra->start = round_down(ra->start, min_nrpages); > ra->size = ra->ra_pages; > ra->async_size = ra->ra_pages / 4; > ractl._index = ra->start; > - page_cache_ra_order(&ractl, ra, 0); > + page_cache_ra_order(&ractl, ra, min_order); > return fpin; > } > > @@ -3164,7 +3169,9 @@ static struct file *do_async_mmap_readahead(struct vm_fault *vmf, > { > struct file *file = vmf->vma->vm_file; > struct file_ra_state *ra = &file->f_ra; > - DEFINE_READAHEAD(ractl, file, ra, file->f_mapping, vmf->pgoff); > + unsigned int min_nrpages = mapping_min_folio_nrpages(file->f_mapping); > + pgoff_t index = round_down(vmf->pgoff, min_nrpages); > + DEFINE_READAHEAD(ractl, file, ra, file->f_mapping, index); > struct file *fpin = NULL; > unsigned int mmap_miss; > > @@ -3212,13 +3219,17 @@ vm_fault_t filemap_fault(struct vm_fault *vmf) > struct file *file = vmf->vma->vm_file; > struct file *fpin = NULL; > struct address_space *mapping = file->f_mapping; > + unsigned int min_order = mapping_min_folio_order(mapping); > + unsigned int nrpages = 1UL << min_order; > struct inode *inode = mapping->host; > - pgoff_t max_idx, index = vmf->pgoff; > + pgoff_t max_idx, index = round_down(vmf->pgoff, nrpages); > struct folio *folio; > vm_fault_t ret = 0; > bool mapping_locked = false; > > max_idx = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); > + max_idx = round_up(max_idx, nrpages); > + Same here. (And the additional whitespace can probably go ...) > if (unlikely(index >= max_idx)) > return VM_FAULT_SIGBUS; > > @@ -3317,13 +3328,17 @@ vm_fault_t filemap_fault(struct vm_fault *vmf) > * We must recheck i_size under page lock. > */ > max_idx = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); > + max_idx = round_up(max_idx, nrpages); > + See above. > if (unlikely(index >= max_idx)) { > folio_unlock(folio); > folio_put(folio); > return VM_FAULT_SIGBUS; > } > > - vmf->page = folio_file_page(folio, index); > + VM_BUG_ON_FOLIO(folio_order(folio) < min_order, folio); > + > + vmf->page = folio_file_page(folio, vmf->pgoff); > return ret | VM_FAULT_LOCKED; > > page_not_uptodate: > @@ -3658,6 +3673,9 @@ static struct folio *do_read_cache_folio(struct address_space *mapping, > { > struct folio *folio; > int err; > + unsigned int min_nrpages = mapping_min_folio_nrpages(mapping); > + > + index = round_down(index, min_nrpages); > > if (!filler) > filler = mapping->a_ops->read_folio; Cheers, Hannes
> > diff --git a/mm/filemap.c b/mm/filemap.c > > index 750e779c23db..323a8e169581 100644 > > --- a/mm/filemap.c > > +++ b/mm/filemap.c > > @@ -2479,14 +2479,16 @@ static int filemap_get_pages(struct kiocb *iocb, size_t count, > > { > > struct file *filp = iocb->ki_filp; > > struct address_space *mapping = filp->f_mapping; > > + unsigned int min_nrpages = mapping_min_folio_nrpages(mapping); > > struct file_ra_state *ra = &filp->f_ra; > > - pgoff_t index = iocb->ki_pos >> PAGE_SHIFT; > > + pgoff_t index = round_down(iocb->ki_pos >> PAGE_SHIFT, min_nrpages); > > pgoff_t last_index; > > struct folio *folio; > > int err = 0; > > /* "last_index" is the index of the page beyond the end of the read */ > > last_index = DIV_ROUND_UP(iocb->ki_pos + count, PAGE_SIZE); > > + last_index = round_up(last_index, min_nrpages); > > Huh? 'last_index' is unset here; sure you mean 'iocb->ki_pos + count' ? > > And what's the rationale to replace 'DIV_ROUND_UP' with 'round_up' ? Actually we are not replacing DIV_ROUND_UP, we are just adding another round_up operation to min_nrpages pages after we get the last_index by converting the bytes to page count. The main idea is to align the last_index to min_order, if it is set. AFAIK, there is no one helper that can do both lines in one shot. > > > retry: > > if (fatal_signal_pending(current)) > > return -EINTR;
On Tue, Feb 13, 2024 at 10:37:01AM +0100, Pankaj Raghav (Samsung) wrote: > From: Luis Chamberlain <mcgrof@kernel.org> > > Supporting mapping_min_order implies that we guarantee each folio in the > page cache has at least an order of mapping_min_order. So when adding new > folios to the page cache we must ensure the index used is aligned to the > mapping_min_order as the page cache requires the index to be aligned to > the order of the folio. > > A higher order folio than min_order by definition is a multiple of the > min_order. If an index is aligned to an order higher than a min_order, it > will also be aligned to the min order. > > This effectively introduces no new functional changes when min order is > not set other than a few rounding computations that should result in the > same value. > > Signed-off-by: Luis Chamberlain <mcgrof@kernel.org> > Signed-off-by: Pankaj Raghav <p.raghav@samsung.com> > --- > mm/filemap.c | 34 ++++++++++++++++++++++++++-------- > 1 file changed, 26 insertions(+), 8 deletions(-) > > diff --git a/mm/filemap.c b/mm/filemap.c > index 750e779c23db..323a8e169581 100644 > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -2479,14 +2479,16 @@ static int filemap_get_pages(struct kiocb *iocb, size_t count, > { > struct file *filp = iocb->ki_filp; > struct address_space *mapping = filp->f_mapping; > + unsigned int min_nrpages = mapping_min_folio_nrpages(mapping); > struct file_ra_state *ra = &filp->f_ra; > - pgoff_t index = iocb->ki_pos >> PAGE_SHIFT; > + pgoff_t index = round_down(iocb->ki_pos >> PAGE_SHIFT, min_nrpages); This is pretty magic - this patch adds a bunch of what appear to be random rounding operations for some undocumented reason. > pgoff_t last_index; > struct folio *folio; > int err = 0; > > /* "last_index" is the index of the page beyond the end of the read */ > last_index = DIV_ROUND_UP(iocb->ki_pos + count, PAGE_SIZE); > + last_index = round_up(last_index, min_nrpages); Same here - this is pretty nasty - we round up twice, but no obvious reason as to why the second round up exists or why it can't be done by the DIV_ROUND_UP() call. Just looking at the code it's impossible to reason why this is being done, let alone determine if it has been implemented correctly. > retry: > if (fatal_signal_pending(current)) > return -EINTR; > @@ -2502,8 +2504,7 @@ static int filemap_get_pages(struct kiocb *iocb, size_t count, > if (!folio_batch_count(fbatch)) { > if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_WAITQ)) > return -EAGAIN; > - err = filemap_create_folio(filp, mapping, > - iocb->ki_pos >> PAGE_SHIFT, fbatch); > + err = filemap_create_folio(filp, mapping, index, fbatch); > if (err == AOP_TRUNCATED_PAGE) > goto retry; > return err; > @@ -3095,7 +3096,10 @@ static struct file *do_sync_mmap_readahead(struct vm_fault *vmf) > struct file *file = vmf->vma->vm_file; > struct file_ra_state *ra = &file->f_ra; > struct address_space *mapping = file->f_mapping; > - DEFINE_READAHEAD(ractl, file, ra, mapping, vmf->pgoff); > + unsigned int min_order = mapping_min_folio_order(mapping); > + unsigned int min_nrpages = mapping_min_folio_nrpages(file->f_mapping); Why use file->f_mapping here and not mapping? And why not just unsigned int min_nrpages = 1U < min_order; So it's obvious how the index alignment is related to the folio order? > + pgoff_t index = round_down(vmf->pgoff, min_nrpages); > + DEFINE_READAHEAD(ractl, file, ra, mapping, index); > struct file *fpin = NULL; > unsigned long vm_flags = vmf->vma->vm_flags; > unsigned int mmap_miss; > @@ -3147,10 +3151,11 @@ static struct file *do_sync_mmap_readahead(struct vm_fault *vmf) > */ > fpin = maybe_unlock_mmap_for_io(vmf, fpin); > ra->start = max_t(long, 0, vmf->pgoff - ra->ra_pages / 2); > + ra->start = round_down(ra->start, min_nrpages); Again, another random rounding operation.... > ra->size = ra->ra_pages; > ra->async_size = ra->ra_pages / 4; > ractl._index = ra->start; > - page_cache_ra_order(&ractl, ra, 0); > + page_cache_ra_order(&ractl, ra, min_order); > return fpin; > } > > @@ -3164,7 +3169,9 @@ static struct file *do_async_mmap_readahead(struct vm_fault *vmf, > { > struct file *file = vmf->vma->vm_file; > struct file_ra_state *ra = &file->f_ra; > - DEFINE_READAHEAD(ractl, file, ra, file->f_mapping, vmf->pgoff); > + unsigned int min_nrpages = mapping_min_folio_nrpages(file->f_mapping); > + pgoff_t index = round_down(vmf->pgoff, min_nrpages); > + DEFINE_READAHEAD(ractl, file, ra, file->f_mapping, index); Ok, this is begging for a new DEFINE_READAHEAD_ALIGNED() macro which internally grabs the mapping_min_folio_nrpages() from the mapping passed to the macro. > struct file *fpin = NULL; > unsigned int mmap_miss; > > @@ -3212,13 +3219,17 @@ vm_fault_t filemap_fault(struct vm_fault *vmf) > struct file *file = vmf->vma->vm_file; > struct file *fpin = NULL; > struct address_space *mapping = file->f_mapping; > + unsigned int min_order = mapping_min_folio_order(mapping); > + unsigned int nrpages = 1UL << min_order; You didn't use mapping_min_folio_nrpages() for this. At least initialise all the variables the same way in the same patch! > struct inode *inode = mapping->host; > - pgoff_t max_idx, index = vmf->pgoff; > + pgoff_t max_idx, index = round_down(vmf->pgoff, nrpages); Yup, I can't help but think that with how many times this is being repeated in this patchset that a helper or two is in order: index = mapping_align_start_index(mapping, vmf->pgoff); And then most of the calls to mapping_min_folio_order() and mapping_min_folio_nrpages() can be removed from this code, too. > struct folio *folio; > vm_fault_t ret = 0; > bool mapping_locked = false; > > max_idx = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); > + max_idx = round_up(max_idx, nrpages); max_index = mapping_align_end_index(mapping, DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE)); > if (unlikely(index >= max_idx)) > return VM_FAULT_SIGBUS; > > @@ -3317,13 +3328,17 @@ vm_fault_t filemap_fault(struct vm_fault *vmf) > * We must recheck i_size under page lock. > */ > max_idx = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); > + max_idx = round_up(max_idx, nrpages); Same again: max_index = mapping_align_end_index(mapping, DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE)); > + > if (unlikely(index >= max_idx)) { > folio_unlock(folio); > folio_put(folio); > return VM_FAULT_SIGBUS; > } > > - vmf->page = folio_file_page(folio, index); > + VM_BUG_ON_FOLIO(folio_order(folio) < min_order, folio); > + > + vmf->page = folio_file_page(folio, vmf->pgoff); > return ret | VM_FAULT_LOCKED; > > page_not_uptodate: > @@ -3658,6 +3673,9 @@ static struct folio *do_read_cache_folio(struct address_space *mapping, > { > struct folio *folio; > int err; > + unsigned int min_nrpages = mapping_min_folio_nrpages(mapping); > + > + index = round_down(index, min_nrpages); And more magic rounding. index = mapping_align_start_index(mapping, index); -Dave.
diff --git a/mm/filemap.c b/mm/filemap.c index 750e779c23db..323a8e169581 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2479,14 +2479,16 @@ static int filemap_get_pages(struct kiocb *iocb, size_t count, { struct file *filp = iocb->ki_filp; struct address_space *mapping = filp->f_mapping; + unsigned int min_nrpages = mapping_min_folio_nrpages(mapping); struct file_ra_state *ra = &filp->f_ra; - pgoff_t index = iocb->ki_pos >> PAGE_SHIFT; + pgoff_t index = round_down(iocb->ki_pos >> PAGE_SHIFT, min_nrpages); pgoff_t last_index; struct folio *folio; int err = 0; /* "last_index" is the index of the page beyond the end of the read */ last_index = DIV_ROUND_UP(iocb->ki_pos + count, PAGE_SIZE); + last_index = round_up(last_index, min_nrpages); retry: if (fatal_signal_pending(current)) return -EINTR; @@ -2502,8 +2504,7 @@ static int filemap_get_pages(struct kiocb *iocb, size_t count, if (!folio_batch_count(fbatch)) { if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_WAITQ)) return -EAGAIN; - err = filemap_create_folio(filp, mapping, - iocb->ki_pos >> PAGE_SHIFT, fbatch); + err = filemap_create_folio(filp, mapping, index, fbatch); if (err == AOP_TRUNCATED_PAGE) goto retry; return err; @@ -3095,7 +3096,10 @@ static struct file *do_sync_mmap_readahead(struct vm_fault *vmf) struct file *file = vmf->vma->vm_file; struct file_ra_state *ra = &file->f_ra; struct address_space *mapping = file->f_mapping; - DEFINE_READAHEAD(ractl, file, ra, mapping, vmf->pgoff); + unsigned int min_order = mapping_min_folio_order(mapping); + unsigned int min_nrpages = mapping_min_folio_nrpages(file->f_mapping); + pgoff_t index = round_down(vmf->pgoff, min_nrpages); + DEFINE_READAHEAD(ractl, file, ra, mapping, index); struct file *fpin = NULL; unsigned long vm_flags = vmf->vma->vm_flags; unsigned int mmap_miss; @@ -3147,10 +3151,11 @@ static struct file *do_sync_mmap_readahead(struct vm_fault *vmf) */ fpin = maybe_unlock_mmap_for_io(vmf, fpin); ra->start = max_t(long, 0, vmf->pgoff - ra->ra_pages / 2); + ra->start = round_down(ra->start, min_nrpages); ra->size = ra->ra_pages; ra->async_size = ra->ra_pages / 4; ractl._index = ra->start; - page_cache_ra_order(&ractl, ra, 0); + page_cache_ra_order(&ractl, ra, min_order); return fpin; } @@ -3164,7 +3169,9 @@ static struct file *do_async_mmap_readahead(struct vm_fault *vmf, { struct file *file = vmf->vma->vm_file; struct file_ra_state *ra = &file->f_ra; - DEFINE_READAHEAD(ractl, file, ra, file->f_mapping, vmf->pgoff); + unsigned int min_nrpages = mapping_min_folio_nrpages(file->f_mapping); + pgoff_t index = round_down(vmf->pgoff, min_nrpages); + DEFINE_READAHEAD(ractl, file, ra, file->f_mapping, index); struct file *fpin = NULL; unsigned int mmap_miss; @@ -3212,13 +3219,17 @@ vm_fault_t filemap_fault(struct vm_fault *vmf) struct file *file = vmf->vma->vm_file; struct file *fpin = NULL; struct address_space *mapping = file->f_mapping; + unsigned int min_order = mapping_min_folio_order(mapping); + unsigned int nrpages = 1UL << min_order; struct inode *inode = mapping->host; - pgoff_t max_idx, index = vmf->pgoff; + pgoff_t max_idx, index = round_down(vmf->pgoff, nrpages); struct folio *folio; vm_fault_t ret = 0; bool mapping_locked = false; max_idx = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); + max_idx = round_up(max_idx, nrpages); + if (unlikely(index >= max_idx)) return VM_FAULT_SIGBUS; @@ -3317,13 +3328,17 @@ vm_fault_t filemap_fault(struct vm_fault *vmf) * We must recheck i_size under page lock. */ max_idx = DIV_ROUND_UP(i_size_read(inode), PAGE_SIZE); + max_idx = round_up(max_idx, nrpages); + if (unlikely(index >= max_idx)) { folio_unlock(folio); folio_put(folio); return VM_FAULT_SIGBUS; } - vmf->page = folio_file_page(folio, index); + VM_BUG_ON_FOLIO(folio_order(folio) < min_order, folio); + + vmf->page = folio_file_page(folio, vmf->pgoff); return ret | VM_FAULT_LOCKED; page_not_uptodate: @@ -3658,6 +3673,9 @@ static struct folio *do_read_cache_folio(struct address_space *mapping, { struct folio *folio; int err; + unsigned int min_nrpages = mapping_min_folio_nrpages(mapping); + + index = round_down(index, min_nrpages); if (!filler) filler = mapping->a_ops->read_folio;