On Sat, Apr 30, 2022 at 11:15 AM JeffleXu <jefflexu@xxxxxxxxxxxxxxxxx> wrote:
>
> Hi Xin,
>
> Thanks for the awsome work, which is exacly what we need.
>
>
>
> On 4/29/22 7:38 AM, Xin Yin wrote:
> > Add erofs_fscache_read_folios_async helper which has same on-demand
> > read logic with erofs_fscache_read_folios, also support asynchronously
> > read data from fscache.And change .readahead() to use this new helper.
> >
> > Signed-off-by: Xin Yin <yinxin.x@xxxxxxxxxxxxx>
> > ---
> > fs/erofs/fscache.c | 256 ++++++++++++++++++++++++++++++++++++++++++++++++++---
> > 1 file changed, 245 insertions(+), 11 deletions(-)
> >
> > diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
> > index eaa50692ddba..4241f1cdc30b 100644
> > --- a/fs/erofs/fscache.c
> > +++ b/fs/erofs/fscache.c
> > @@ -5,6 +5,231 @@
> > #include <linux/fscache.h>
> > #include "internal.h"
> >
> > +static void erofs_fscache_put_subrequest(struct netfs_io_subrequest *subreq);
> > +
> > +static struct netfs_io_request *erofs_fscache_alloc_request(struct address_space *mapping,
> > + loff_t start, size_t len)
> > +{
> > + struct netfs_io_request *rreq;
> > +
> > + rreq = kzalloc(sizeof(struct netfs_io_request), GFP_KERNEL);
> > + if (!rreq)
> > + return ERR_PTR(-ENOMEM);
> > +
> > + rreq->start = start;
> > + rreq->len = len;
> > + rreq->mapping = mapping;
> > + INIT_LIST_HEAD(&rreq->subrequests);
> > + refcount_set(&rreq->ref, 1);
> > +
> > + return rreq;
> > +}
> > +
> > +static void erofs_fscache_clear_subrequests(struct netfs_io_request *rreq)
> > +{
> > + struct netfs_io_subrequest *subreq;
> > +
> > + while (!list_empty(&rreq->subrequests)) {
> > + subreq = list_first_entry(&rreq->subrequests,
> > + struct netfs_io_subrequest, rreq_link);
> > + list_del(&subreq->rreq_link);
> > + erofs_fscache_put_subrequest(subreq);
> > + }
> > +}
> > +
>
>
> > +static void erofs_fscache_free_request(struct netfs_io_request *rreq)
> > +{
> > + erofs_fscache_clear_subrequests(rreq);
>
> Actually I don't underdtand why erofs_fscache_clear_subrequests() is
> needed here. erofs_fscache_free_request() is called only when rreq->ref
> has been decreased to 0. That means there's already no subrequest, or
> rreq->ref won't be 0 since each subrequest maintains one refcount of
> rreq. Though I know it's a copy from netfs_free_request()...
>
Yes, for now most of the procedures are implemented with reference to
netfs. And yeah, I think at least in our scenario this is not needed,
I will remove it in the next version , and do further checks and
tests.
>
> > + if (rreq->cache_resources.ops)
> > + rreq->cache_resources.ops->end_operation(&rreq->cache_resources);
> > + kfree(rreq);
> > +}
> > +
> > +static void erofs_fscache_put_request(struct netfs_io_request *rreq)
> > +{
> > + bool dead;
> > +
> > + dead = refcount_dec_and_test(&rreq->ref);
> > + if (dead)
> > + erofs_fscache_free_request(rreq);
> > +}
>
> How about making erofs_fscache_free_request() folded inside
> erofs_fscache_put_request(), since here each function is quite short?
>
> Besides, how about
>
> if (refcount_dec_and_test(&rreq->ref)) {
> /* erofs_fscache_free_request */
> }
>
Yes , this should be better. will fix it in next version.
>
> > +
> > +
> > +static struct netfs_io_subrequest *
> > + erofs_fscache_alloc_subrequest(struct netfs_io_request *rreq)
> > +{
> > + struct netfs_io_subrequest *subreq;
> > +
> > + subreq = kzalloc(sizeof(struct netfs_io_subrequest), GFP_KERNEL);
> > + if (subreq) {
> > + INIT_LIST_HEAD(&subreq->rreq_link);
> > + refcount_set(&subreq->ref, 2);
> > + subreq->rreq = rreq;
> > + refcount_inc(&rreq->ref);
> > + }
> > +
> > + return subreq;
> > +}
> > +
>
>
> > +static void erofs_fscache_free_subrequest(struct netfs_io_subrequest *subreq)
> > +{
> > + struct netfs_io_request *rreq = subreq->rreq;
> > +
> > + kfree(subreq);
> > + erofs_fscache_put_request(rreq);
> > +}
> > +
> > +static void erofs_fscache_put_subrequest(struct netfs_io_subrequest *subreq)
> > +{
> > + bool dead;
> > +
> > + dead = refcount_dec_and_test(&subreq->ref);
> > + if (dead)
> > + erofs_fscache_free_subrequest(subreq);
> > +}
>
> Similar to the issue of erofs_fscache_put_request().
>
Will fix it.
>
> > +
> > +
> > +static void erofs_fscache_rreq_unlock_folios(struct netfs_io_request *rreq)
> > +{
> > + struct netfs_io_subrequest *subreq;
> > + struct folio *folio;
> > + unsigned int iopos;
> > + pgoff_t start_page = rreq->start / PAGE_SIZE;
> > + pgoff_t last_page = ((rreq->start + rreq->len) / PAGE_SIZE) - 1;
> > + bool subreq_failed = false;
> > +
> > + XA_STATE(xas, &rreq->mapping->i_pages, start_page);
> > +
> > + subreq = list_first_entry(&rreq->subrequests,
> > + struct netfs_io_subrequest, rreq_link);
> > + iopos = 0;
> > + subreq_failed = (subreq->error < 0);
> > +
> > + rcu_read_lock();
> > + xas_for_each(&xas, folio, last_page) {
> > + unsigned int pgpos = (folio_index(folio) - start_page) * PAGE_SIZE;
> > + unsigned int pgend = pgpos + folio_size(folio);
> > + bool pg_failed = false;
> > +
> > + for (;;) {
> > + if (!subreq) {
> > + pg_failed = true;
> > + break;
> > + }
> > +
> > + pg_failed |= subreq_failed;
> > + if (pgend < iopos + subreq->len)
> > + break;
> > +
> > + iopos += subreq->len;
> > + if (!list_is_last(&subreq->rreq_link, &rreq->subrequests)) {
> > + subreq = list_next_entry(subreq, rreq_link);
> > + subreq_failed = (subreq->error < 0);
> > + } else {
> > + subreq = NULL;
> > + subreq_failed = false;
> > + }
> > + if (pgend == iopos)
> > + break;
> > + }
> > +
> > + if (!pg_failed)
> > + folio_mark_uptodate(folio);
> > +
> > + folio_unlock(folio);
> > + }
> > + rcu_read_unlock();
> > +}
> > +
> > +
> > +static void erofs_fscache_rreq_complete(struct netfs_io_request *rreq)
> > +{
> > + erofs_fscache_rreq_unlock_folios(rreq);
> > + erofs_fscache_clear_subrequests(rreq);
> > + erofs_fscache_put_request(rreq);
> > +}
> > +
> > +static void erofc_fscache_subreq_complete(void *priv, ssize_t transferred_or_error,
> > + bool was_async)
> > +{
> > + struct netfs_io_subrequest *subreq = priv;
> > + struct netfs_io_request *rreq = subreq->rreq;
> > +
> > + if (IS_ERR_VALUE(transferred_or_error))
> > + subreq->error = transferred_or_error;
> > +
> > + if (atomic_dec_and_test(&rreq->nr_outstanding))
> > + erofs_fscache_rreq_complete(rreq);
> > +
> > + erofs_fscache_put_subrequest(subreq);
> > +}
> > +
> > +static int erofs_fscache_read_folios_async(struct fscache_cookie *cookie,
> > + struct netfs_io_request *rreq,
> > + loff_t start, size_t len,
> > + loff_t pstart)
> > +{
> > + enum netfs_io_source source;
> > + struct netfs_io_subrequest *subreq;
> > + struct netfs_cache_resources *cres;
> > + struct iov_iter iter;
> > + size_t done = 0;
> > + int ret;
> > +
> > + atomic_set(&rreq->nr_outstanding, 1);
> > +
> > + cres = &rreq->cache_resources;
> > + ret = fscache_begin_read_operation(cres, cookie);
> > + if (ret)
> > + goto out;
> > +
> > + while (done < len) {
> > + subreq = erofs_fscache_alloc_subrequest(rreq);
> > + if (!subreq) {
> > + ret = -ENOMEM;
> > + goto out;
> > + }
> > +
> > + subreq->start = pstart + done;
> > + subreq->len = len - done;
> > + subreq->flags = 1 << NETFS_SREQ_ONDEMAND;
> > +
> > + list_add_tail(&subreq->rreq_link, &rreq->subrequests);
> > +
> > + source = cres->ops->prepare_read(subreq, LLONG_MAX);
> > + if (WARN_ON(subreq->len == 0))
> > + source = NETFS_INVALID_READ;
> > + if (source != NETFS_READ_FROM_CACHE) {
> > + ret = -EIO;
> > + erofs_fscache_put_subrequest(subreq);
> > + goto out;
>
> Need to set subreq->error here before going to out?
>
Make sense , I think this issue may cause some pages to be
incorrectly set to uptodate. I will fix this in next version , and do
further exception tests.
>
> > + }
> > +
> > + atomic_inc(&rreq->nr_outstanding);
> > +
> > + iov_iter_xarray(&iter, READ, &rreq->mapping->i_pages,
> > + start + done, subreq->len);
> > +
> > + ret = fscache_read(cres, subreq->start, &iter,
> > + NETFS_READ_HOLE_FAIL, erofc_fscache_subreq_complete, subreq);
> > +
> > + if (ret == -EIOCBQUEUED)
> > + ret = 0;
> > +
> > + if (ret) {
> > + erofs_fscache_put_subrequest(subreq);
>
> I think erofs_fscache_put_subrequest() here is not needed, since when
> error encountered, erofc_fscache_subreq_complete() will be called inside
> fscache_read(), in which erofs_fscache_put_subrequest() will be called
> already.
>
yes , will remove it in the next version.
> > + goto out;
> > + }
> > +
> > + done += subreq->len;
> > + }
> > +out:
> > + if (atomic_dec_and_test(&rreq->nr_outstanding))
> > + erofs_fscache_rreq_complete(rreq);
> > +
> > + return ret;
> > +}
> BTW, could you please also help covert the original synchronous
> erofs_fscache_read_folios() to calling erofs_fscache_read_folios_async()
> to avoid code duplication?
>
Yeah , I will do this in the next version.
Thank,
Xin Yin
> > +
> > /*
> > * Read data from fscache and fill the read data into page cache described by
> > * @start/len, which shall be both aligned with PAGE_SIZE. @pstart describes
> > @@ -163,15 +388,16 @@ static int erofs_fscache_readpage(struct file *file, struct page *page)
> > return ret;
> > }
> >
> > -static void erofs_fscache_unlock_folios(struct readahead_control *rac,
> > - size_t len)
> > +static void erofs_fscache_readahead_folios(struct readahead_control *rac,
> > + size_t len, bool unlock)
> > {
> > while (len) {
> > struct folio *folio = readahead_folio(rac);
> > -
> > len -= folio_size(folio);
> > - folio_mark_uptodate(folio);
> > - folio_unlock(folio);
> > + if (unlock) {
> > + folio_mark_uptodate(folio);
> > + folio_unlock(folio);
> > + }
> > }
> > }
> >
> > @@ -193,6 +419,7 @@ static void erofs_fscache_readahead(struct readahead_control *rac)
> > do {
> > struct erofs_map_blocks map;
> > struct erofs_map_dev mdev;
> > + struct netfs_io_request *rreq;
> >
> > pos = start + done;
> > map.m_la = pos;
> > @@ -212,7 +439,7 @@ static void erofs_fscache_readahead(struct readahead_control *rac)
> > offset, count);
> > iov_iter_zero(count, &iter);
> >
> > - erofs_fscache_unlock_folios(rac, count);
> > + erofs_fscache_readahead_folios(rac, count, true);
> > ret = count;
> > continue;
> > }
> > @@ -238,13 +465,20 @@ static void erofs_fscache_readahead(struct readahead_control *rac)
> > if (ret)
> > return;
> >
> > - ret = erofs_fscache_read_folios(mdev.m_fscache->cookie,
> > - rac->mapping, offset, count,
> > + rreq = erofs_fscache_alloc_request(rac->mapping, offset, count);
> > + if (IS_ERR(rreq))
> > + return;
> > + /*
> > + * Drop the ref of folios here. Unlock them in
> > + * rreq_unlock_folios() when rreq complete.
> > + */
> > + erofs_fscache_readahead_folios(rac, count, false);
> > + ret = erofs_fscache_read_folios_async(mdev.m_fscache->cookie,
> > + rreq, offset, count,
> > mdev.m_pa + (pos - map.m_la));
> > - if (!ret) {
> > - erofs_fscache_unlock_folios(rac, count);
> > +
> > + if (!ret)
> > ret = count;
> > - }
> > } while (ret > 0 && ((done += ret) < len));
> > }
> >
>
>
>
> --
> Thanks,
> Jeffle
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