On 5/5/25 16:40, Darrick J. Wong wrote:
> On Sun, May 04, 2025 at 09:13:44PM +0200, Bernd Schubert wrote:
>>
>>
>> On 4/26/25 02:08, Joanne Koong wrote:
>>> Add support for folios larger than one page size for readahead.
>>>
>>> Signed-off-by: Joanne Koong <joannelkoong@xxxxxxxxx>
>>> Reviewed-by: Jeff Layton <jlayton@xxxxxxxxxx>
>>> ---
>>> fs/fuse/file.c | 36 +++++++++++++++++++++++++++---------
>>> 1 file changed, 27 insertions(+), 9 deletions(-)
>>>
>>> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
>>> index 1d38486fae50..9a31f2a516b9 100644
>>> --- a/fs/fuse/file.c
>>> +++ b/fs/fuse/file.c
>>> @@ -876,14 +876,13 @@ static void fuse_readpages_end(struct fuse_mount *fm, struct fuse_args *args,
>>> fuse_io_free(ia);
>>> }
>>>
>>> -static void fuse_send_readpages(struct fuse_io_args *ia, struct file *file)
>>> +static void fuse_send_readpages(struct fuse_io_args *ia, struct file *file,
>>> + unsigned int count)
>>> {
>>> struct fuse_file *ff = file->private_data;
>>> struct fuse_mount *fm = ff->fm;
>>> struct fuse_args_pages *ap = &ia->ap;
>>> loff_t pos = folio_pos(ap->folios[0]);
>>> - /* Currently, all folios in FUSE are one page */
>>> - size_t count = ap->num_folios << PAGE_SHIFT;
>>> ssize_t res;
>>> int err;
>>>
>>> @@ -918,6 +917,7 @@ static void fuse_readahead(struct readahead_control *rac)
>>> struct inode *inode = rac->mapping->host;
>>> struct fuse_conn *fc = get_fuse_conn(inode);
>>> unsigned int max_pages, nr_pages;
>>> + struct folio *folio = NULL;
>>>
>>> if (fuse_is_bad(inode))
>>> return;
>>> @@ -939,8 +939,8 @@ static void fuse_readahead(struct readahead_control *rac)
>>> while (nr_pages) {
>>> struct fuse_io_args *ia;
>>> struct fuse_args_pages *ap;
>>> - struct folio *folio;
>>> unsigned cur_pages = min(max_pages, nr_pages);
>>> + unsigned int pages = 0;
>>>
>>> if (fc->num_background >= fc->congestion_threshold &&
>>> rac->ra->async_size >= readahead_count(rac))
>>> @@ -952,10 +952,12 @@ static void fuse_readahead(struct readahead_control *rac)
>>>
>>> ia = fuse_io_alloc(NULL, cur_pages);
>>> if (!ia)
>>> - return;
>>> + break;
>>> ap = &ia->ap;
>>>
>>> - while (ap->num_folios < cur_pages) {
>>> + while (pages < cur_pages) {
>>> + unsigned int folio_pages;
>>> +
>>> /*
>>> * This returns a folio with a ref held on it.
>>> * The ref needs to be held until the request is
>>> @@ -963,13 +965,29 @@ static void fuse_readahead(struct readahead_control *rac)
>>> * fuse_try_move_page()) drops the ref after it's
>>> * replaced in the page cache.
>>> */
>>> - folio = __readahead_folio(rac);
>>> + if (!folio)
>>> + folio = __readahead_folio(rac);
>>> +
>>> + folio_pages = folio_nr_pages(folio);
>>> + if (folio_pages > cur_pages - pages)
>>> + break;
>>> +
>>
>> Hmm, so let's assume this would be a 2MB folio, but fc->max_pages is
>> limited to 1MB - we not do read-ahead anymore?
>
> It's hard for me to say without seeing the actual enablement patches,
> but filesystems are supposed to call mapping_set_folio_order_range to
> constrain the sizes of the folios that the pagecache requests.
I think large folios do not get enabled ye in this series. Could we have
a comment here that folio size is supposed to be restricted to
fc->max_pages? And wouldn't that be a case for unlikely()?
Thanks,
Bernd
