| Message ID | 20200217184613.19668-6-willy@infradead.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | None | expand |
On 2/17/20 10:45 AM, Matthew Wilcox wrote: > From: "Matthew Wilcox (Oracle)" <willy@infradead.org> > > Eliminate the page_offset variable which was just confusing; > record the start of each consecutive run of pages in the OK...presumably for the benefit of a following patch, since it is not actually consumed in this patch. > readahead_control, and move the 'kick off a fresh batch' code to > the end of the function for easier use in the next patch. That last bit was actually done in the previous patch, rather than this one, right? > > Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org> > --- > mm/readahead.c | 31 +++++++++++++++++++------------ > 1 file changed, 19 insertions(+), 12 deletions(-) > > diff --git a/mm/readahead.c b/mm/readahead.c > index 15329309231f..74791b96013f 100644 > --- a/mm/readahead.c > +++ b/mm/readahead.c > @@ -154,7 +154,6 @@ 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); > int page_idx; > @@ -163,6 +162,7 @@ void __do_page_cache_readahead(struct address_space *mapping, > struct readahead_control rac = { > .mapping = mapping, > .file = filp, > + ._start = offset, > ._nr_pages = 0, > }; > > @@ -175,32 +175,39 @@ void __do_page_cache_readahead(struct address_space *mapping, > * Preallocate as many pages as we will need. > */ > for (page_idx = 0; page_idx < nr_to_read; page_idx++) { > - pgoff_t page_offset = offset + page_idx; You know...this ends up incrementing offset each time through the loop, so yes, the behavior is the same as when using "offset + page_idx". However, now it's a little harder to see that. IMHO the page_offset variable is not actually a bad thing, here. I'd rather keep it, all other things being equal (and I don't see any other benefits here: line count is the same, for example). What do you think? thanks,
On 2/18/20 2:57 PM, John Hubbard wrote: > On 2/17/20 10:45 AM, Matthew Wilcox wrote: >> From: "Matthew Wilcox (Oracle)" <willy@infradead.org> >> >> Eliminate the page_offset variable which was just confusing; >> record the start of each consecutive run of pages in the > > Darn it, I incorrectly reviewed the N/16 patch, instead of the N/19, for this one. I thought I had deleted all those! Let me try again with the correct patch, sorry!! thanks,
diff --git a/mm/readahead.c b/mm/readahead.c index 15329309231f..74791b96013f 100644 --- a/mm/readahead.c +++ b/mm/readahead.c @@ -154,7 +154,6 @@ 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); int page_idx; @@ -163,6 +162,7 @@ void __do_page_cache_readahead(struct address_space *mapping, struct readahead_control rac = { .mapping = mapping, .file = filp, + ._start = offset, ._nr_pages = 0, }; @@ -175,32 +175,39 @@ void __do_page_cache_readahead(struct address_space *mapping, * Preallocate as many pages as we will need. */ for (page_idx = 0; page_idx < nr_to_read; page_idx++) { - pgoff_t page_offset = offset + page_idx; + struct page *page; - if (page_offset > end_index) + if (offset > end_index) break; - page = xa_load(&mapping->i_pages, page_offset); + page = xa_load(&mapping->i_pages, offset); if (page && !xa_is_value(page)) { /* - * Page already present? Kick off the current batch of - * contiguous pages before continuing with the next - * batch. + * Page already present? Kick off the current batch + * of contiguous pages before continuing with the + * next batch. This page may be the one we would + * have intended to mark as Readahead, but we don't + * have a stable reference to this page, and it's + * not worth getting one just for that. */ - if (readahead_count(&rac)) - read_pages(&rac, &page_pool, gfp_mask); - rac._nr_pages = 0; - continue; + goto read; } page = __page_cache_alloc(gfp_mask); if (!page) break; - page->index = page_offset; + page->index = offset; list_add(&page->lru, &page_pool); if (page_idx == nr_to_read - lookahead_size) SetPageReadahead(page); rac._nr_pages++; + offset++; + continue; +read: + if (readahead_count(&rac)) + read_pages(&rac, &page_pool, gfp_mask); + rac._nr_pages = 0; + rac._start = ++offset; } /*