| Message ID | 20200323202259.13363-13-willy@infradead.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Change readahead API | expand |
On Mon, Mar 23, 2020 at 01:22:46PM -0700, Matthew Wilcox wrote: > From: "Matthew Wilcox (Oracle)" <willy@infradead.org> > > By reducing nr_to_read, we can eliminate this check from inside the loop. > > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> > Reviewed-by: John Hubbard <jhubbard@nvidia.com> > Reviewed-by: William Kucharski <william.kucharski@oracle.com> > --- > mm/readahead.c | 14 ++++++++------ > 1 file changed, 8 insertions(+), 6 deletions(-) > > diff --git a/mm/readahead.c b/mm/readahead.c > index d01531ef9f3c..998fdd23c0b1 100644 > --- a/mm/readahead.c > +++ b/mm/readahead.c > @@ -167,8 +167,6 @@ void __do_page_cache_readahead(struct address_space *mapping, > unsigned long lookahead_size) > { > struct inode *inode = mapping->host; > - struct page *page; > - unsigned long end_index; /* The last page we want to read */ > LIST_HEAD(page_pool); > loff_t isize = i_size_read(inode); > gfp_t gfp_mask = readahead_gfp_mask(mapping); > @@ -178,22 +176,26 @@ void __do_page_cache_readahead(struct address_space *mapping, > ._index = index, > }; > unsigned long i; > + pgoff_t end_index; /* The last page we want to read */ > > if (isize == 0) > return; > > - end_index = ((isize - 1) >> PAGE_SHIFT); > + end_index = (isize - 1) >> PAGE_SHIFT; > + if (index > end_index) > + return; > + /* Don't read past the page containing the last byte of the file */ > + if (nr_to_read > end_index - index) > + nr_to_read = end_index - index + 1; > > /* > * Preallocate as many pages as we will need. > */ > for (i = 0; i < nr_to_read; i++) { > - if (index + i > end_index) > - break; > + struct page *page = xa_load(&mapping->i_pages, index + i); > > BUG_ON(index + i != rac._index + rac._nr_pages); > > - page = xa_load(&mapping->i_pages, index + i); > if (page && !xa_is_value(page)) { > /* > * Page already present? Kick off the current batch of > -- Reviewed-by: Eric Biggers <ebiggers@google.com> - Eric
On Mon, Mar 23, 2020 at 01:22:46PM -0700, Matthew Wilcox wrote: > From: "Matthew Wilcox (Oracle)" <willy@infradead.org> > > By reducing nr_to_read, we can eliminate this check from inside the loop. > > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> > Reviewed-by: John Hubbard <jhubbard@nvidia.com> > Reviewed-by: William Kucharski <william.kucharski@oracle.com> Looks good, Reviewed-by: Christoph Hellwig <hch@lst.de>
diff --git a/mm/readahead.c b/mm/readahead.c index d01531ef9f3c..998fdd23c0b1 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -167,8 +167,6 @@ void __do_page_cache_readahead(struct address_space *mapping, unsigned long lookahead_size) { struct inode *inode = mapping->host; - struct page *page; - unsigned long end_index; /* The last page we want to read */ LIST_HEAD(page_pool); loff_t isize = i_size_read(inode); gfp_t gfp_mask = readahead_gfp_mask(mapping); @@ -178,22 +176,26 @@ void __do_page_cache_readahead(struct address_space *mapping, ._index = index, }; unsigned long i; + pgoff_t end_index; /* The last page we want to read */ if (isize == 0) return; - end_index = ((isize - 1) >> PAGE_SHIFT); + end_index = (isize - 1) >> PAGE_SHIFT; + if (index > end_index) + return; + /* Don't read past the page containing the last byte of the file */ + if (nr_to_read > end_index - index) + nr_to_read = end_index - index + 1; /* * Preallocate as many pages as we will need. */ for (i = 0; i < nr_to_read; i++) { - if (index + i > end_index) - break; + struct page *page = xa_load(&mapping->i_pages, index + i); BUG_ON(index + i != rac._index + rac._nr_pages); - page = xa_load(&mapping->i_pages, index + i); if (page && !xa_is_value(page)) { /* * Page already present? Kick off the current batch of