| Message ID | 20201102184312.25926-12-willy@infradead.org (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Refactor generic_file_buffered_read | expand |
On Mon, Nov 02, 2020 at 06:43:06PM +0000, Matthew Wilcox (Oracle) wrote: > Move the complicated condition and the calculations out of > filemap_update_page() into its own function. You're missing a signed-off-by Reviewed-by: Kent Overstreet <kent.overstreet@gmail.com>
On Mon, Nov 02, 2020 at 02:50:56PM -0500, Kent Overstreet wrote: > On Mon, Nov 02, 2020 at 06:43:06PM +0000, Matthew Wilcox (Oracle) wrote: > > Move the complicated condition and the calculations out of > > filemap_update_page() into its own function. > > You're missing a signed-off-by > > Reviewed-by: Kent Overstreet <kent.overstreet@gmail.com> Oops. Signed-off-by: Matthew Wilcox (Oracle) <willy@infradead.org>
On Mon, Nov 02, 2020 at 06:43:06PM +0000, Matthew Wilcox (Oracle) wrote: > Move the complicated condition and the calculations out of > filemap_update_page() into its own function. The logic looks good, but the flow inside of filemap_update_page looks odd. The patch below relative to this commit shows how I'd do it: diff --git a/mm/filemap.c b/mm/filemap.c index 81b569d818a3f8..304180c022d38a 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2266,40 +2266,39 @@ static int filemap_update_page(struct kiocb *iocb, if (!trylock_page(page)) { if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_NOIO)) goto error; - if (iocb->ki_flags & IOCB_WAITQ) { - if (!first) - goto error; - error = __lock_page_async(page, iocb->ki_waitq); - if (error) - goto error; - } else { + if (!(iocb->ki_flags & IOCB_WAITQ)) { put_and_wait_on_page_locked(page, TASK_KILLABLE); return AOP_TRUNCATED_PAGE; } + if (!first) + goto error; + error = __lock_page_async(page, iocb->ki_waitq); + if (error) + goto error; } + error = AOP_TRUNCATED_PAGE; if (!page->mapping) - goto truncated; - if (filemap_range_uptodate(iocb, mapping, iter, page)) { - unlock_page(page); - return 0; - } + goto error_unlock_page; - if (iocb->ki_flags & (IOCB_NOIO | IOCB_NOWAIT | IOCB_WAITQ)) { - unlock_page(page); + if (!filemap_range_uptodate(iocb, mapping, iter, page)) { error = -EAGAIN; - } else { + if (iocb->ki_flags & (IOCB_NOIO | IOCB_NOWAIT | IOCB_WAITQ)) + goto error_unlock_page; error = filemap_read_page(iocb->ki_filp, mapping, page); - if (!error) - return 0; + if (error) + goto error; + return 0; /* filemap_read_page unlocks the page */ } + + unlock_page(page); + return 0; + +error_unlock_page: + unlock_page(page); error: put_page(page); return error; -truncated: - unlock_page(page); - put_page(page); - return AOP_TRUNCATED_PAGE; } static struct page *filemap_create_page(struct file *file,
On Tue, Nov 03, 2020 at 08:49:44AM +0100, Christoph Hellwig wrote: > On Mon, Nov 02, 2020 at 06:43:06PM +0000, Matthew Wilcox (Oracle) wrote: > > Move the complicated condition and the calculations out of > > filemap_update_page() into its own function. > > The logic looks good, but the flow inside of filemap_update_page looks > odd. The patch below relative to this commit shows how I'd do it: I have a simplification in mind that gets rid of the awkward 'first' parameter. In filemap_get_pages(), do: if ((iocb->ki_flags & IOCB_WAITQ) && (pagevec_count(pvec) > 1)) iocb->ki_flags |= IOCB_NOWAIT; before calling filemap_update_page(). That matches what Kent did in filemap_read(): if ((iocb->ki_flags & IOCB_WAITQ) && already_read) iocb->ki_flags |= IOCB_NOWAIT; > diff --git a/mm/filemap.c b/mm/filemap.c > index 81b569d818a3f8..304180c022d38a 100644 > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -2266,40 +2266,39 @@ static int filemap_update_page(struct kiocb *iocb, > if (!trylock_page(page)) { > if (iocb->ki_flags & (IOCB_NOWAIT | IOCB_NOIO)) > goto error; > - if (iocb->ki_flags & IOCB_WAITQ) { > - if (!first) > - goto error; > - error = __lock_page_async(page, iocb->ki_waitq); > - if (error) > - goto error; > - } else { > + if (!(iocb->ki_flags & IOCB_WAITQ)) { > put_and_wait_on_page_locked(page, TASK_KILLABLE); > return AOP_TRUNCATED_PAGE; > } > + if (!first) > + goto error; > + error = __lock_page_async(page, iocb->ki_waitq); > + if (error) > + goto error; > } I see where you're going there. OK. > > + error = AOP_TRUNCATED_PAGE; > if (!page->mapping) > - goto truncated; > - if (filemap_range_uptodate(iocb, mapping, iter, page)) { > - unlock_page(page); > - return 0; > - } > + goto error_unlock_page; > > - if (iocb->ki_flags & (IOCB_NOIO | IOCB_NOWAIT | IOCB_WAITQ)) { > - unlock_page(page); > + if (!filemap_range_uptodate(iocb, mapping, iter, page)) { > error = -EAGAIN; > - } else { > + if (iocb->ki_flags & (IOCB_NOIO | IOCB_NOWAIT | IOCB_WAITQ)) > + goto error_unlock_page; > error = filemap_read_page(iocb->ki_filp, mapping, page); > - if (!error) > - return 0; > + if (error) > + goto error; > + return 0; /* filemap_read_page unlocks the page */ > } > + > + unlock_page(page); > + return 0; > + > +error_unlock_page: > + unlock_page(page); > error: > put_page(page); > return error; > -truncated: > - unlock_page(page); > - put_page(page); > - return AOP_TRUNCATED_PAGE; > } There's something niggling at me about this change ... I'll play with it a bit.
On Tue, Nov 03, 2020 at 03:18:47PM +0000, Matthew Wilcox wrote: > I have a simplification in mind that gets rid of the awkward 'first' > parameter. In filemap_get_pages(), do: > > if ((iocb->ki_flags & IOCB_WAITQ) && (pagevec_count(pvec) > 1)) > iocb->ki_flags |= IOCB_NOWAIT; > > before calling filemap_update_page(). That matches what Kent did in > filemap_read(): Yes, that makes a lot of sense. No need for the second pair of inner braces, though :)
On Tue, Nov 03, 2020 at 04:31:18PM +0100, Christoph Hellwig wrote: > On Tue, Nov 03, 2020 at 03:18:47PM +0000, Matthew Wilcox wrote: > > I have a simplification in mind that gets rid of the awkward 'first' > > parameter. In filemap_get_pages(), do: > > > > if ((iocb->ki_flags & IOCB_WAITQ) && (pagevec_count(pvec) > 1)) > > iocb->ki_flags |= IOCB_NOWAIT; > > > > before calling filemap_update_page(). That matches what Kent did in > > filemap_read(): > > Yes, that makes a lot of sense. No need for the second pair of inner > braces, though :) I wrote it as if ((iocb->ki_flags & IOCB_WAITQ) && pagevec_count(pvec) > 1) originally, and then talked myself into putting the unnecessary brackets in to make it look more symmetric ;-)
diff --git a/mm/filemap.c b/mm/filemap.c index 41b90243f4ee..81b569d818a3 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -2228,11 +2228,39 @@ static int filemap_read_page(struct file *file, struct address_space *mapping, return error; } +static bool filemap_range_uptodate(struct kiocb *iocb, + struct address_space *mapping, struct iov_iter *iter, + struct page *page) +{ + loff_t pos; + int count; + + if (PageUptodate(page)) + return true; + /* pipes can't handle partially uptodate pages */ + if (iov_iter_is_pipe(iter)) + return false; + if (!mapping->a_ops->is_partially_uptodate) + return false; + if (mapping->host->i_blkbits >= (PAGE_SHIFT + thp_order(page))) + return false; + + pos = (loff_t) page->index << PAGE_SHIFT; + if (pos > iocb->ki_pos) { + count = iocb->ki_pos + iter->count - pos; + pos = 0; + } else { + count = iter->count; + pos = iocb->ki_pos & (thp_size(page) - 1); + } + + return mapping->a_ops->is_partially_uptodate(page, pos, count); +} + static int filemap_update_page(struct kiocb *iocb, struct address_space *mapping, struct iov_iter *iter, struct page *page, loff_t pos, loff_t count, bool first) { - struct inode *inode = mapping->host; int error = -EAGAIN; if (!trylock_page(page)) { @@ -2252,22 +2280,11 @@ static int filemap_update_page(struct kiocb *iocb, if (!page->mapping) goto truncated; - if (PageUptodate(page)) - goto uptodate; - if (inode->i_blkbits == PAGE_SHIFT || - !mapping->a_ops->is_partially_uptodate) - goto readpage; - /* pipes can't handle partially uptodate pages */ - if (unlikely(iov_iter_is_pipe(iter))) - goto readpage; - if (!mapping->a_ops->is_partially_uptodate(page, - pos & (thp_size(page) - 1), count)) - goto readpage; -uptodate: - unlock_page(page); - return 0; + if (filemap_range_uptodate(iocb, mapping, iter, page)) { + unlock_page(page); + return 0; + } -readpage: if (iocb->ki_flags & (IOCB_NOIO | IOCB_NOWAIT | IOCB_WAITQ)) { unlock_page(page); error = -EAGAIN;