[PATCH v6 29/30] afs: Use new netfs lib read helper API

From: David Howells
Date: Thu Apr 08 2021 - 10:11:59 EST

Make AFS use the new netfs read helpers to implement the VM read
operations:

- afs_readpage() now hands off responsibility to netfs_readpage().

- afs_readpages() is gone and replaced with afs_readahead().

- afs_readahead() just hands off responsibility to netfs_readahead().

These make use of the cache if a cookie is supplied, otherwise just call
the ->issue_op() method a sufficient number of times to complete the entire
request.

Changes:
v5:
- Use proper wait function for PG_fscache in afs_page_mkwrite()[1].
- Use killable wait for PG_writeback in afs_page_mkwrite()[1].

v4:
- Folded in error handling fixes to afs_req_issue_op().
- Added flag to netfs_subreq_terminated() to indicate that the caller may
have been running async and stuff that might sleep needs punting to a
workqueue.

Signed-off-by: David Howells <dhowells@xxxxxxxxxx>
cc: linux-afs@xxxxxxxxxxxxxxxxxxx
cc: linux-cachefs@xxxxxxxxxx
cc: linux-fsdevel@xxxxxxxxxxxxxxx
Link: https://lore.kernel.org/r/2499407.1616505440@xxxxxxxxxxxxxxxxxxxxxx [1]
Link: https://lore.kernel.org/r/160588542733.3465195.7526541422073350302.stgit@xxxxxxxxxxxxxxxxxxxxxx/ # rfc
Link: https://lore.kernel.org/r/161118158436.1232039.3884845981224091996.stgit@xxxxxxxxxxxxxxxxxxxxxx/ # rfc
Link: https://lore.kernel.org/r/161161053540.2537118.14904446369309535330.stgit@xxxxxxxxxxxxxxxxxxxxxx/ # v2
Link: https://lore.kernel.org/r/161340418739.1303470.5908092911600241280.stgit@xxxxxxxxxxxxxxxxxxxxxx/ # v3
Link: https://lore.kernel.org/r/161539561926.286939.5729036262354802339.stgit@xxxxxxxxxxxxxxxxxxxxxx/ # v4
Link: https://lore.kernel.org/r/161653817977.2770958.17696456811587237197.stgit@xxxxxxxxxxxxxxxxxxxxxx/ # v5
---

fs/afs/Kconfig | 1
fs/afs/file.c | 327 +++++++++++++----------------------------------------
fs/afs/fsclient.c | 1
fs/afs/internal.h | 3
fs/afs/write.c | 7 +
5 files changed, 88 insertions(+), 251 deletions(-)

diff --git a/fs/afs/Kconfig b/fs/afs/Kconfig
index 1ad211d72b3b..fc8ba9142f2f 100644
--- a/fs/afs/Kconfig
+++ b/fs/afs/Kconfig
@@ -4,6 +4,7 @@ config AFS_FS
depends on INET
select AF_RXRPC
select DNS_RESOLVER
+ select NETFS_SUPPORT
help
If you say Y here, you will get an experimental Andrew File System
driver. It currently only supports unsecured read-only AFS access.
diff --git a/fs/afs/file.c b/fs/afs/file.c
index 2db810467d3f..10c6eaaac2cc 100644
--- a/fs/afs/file.c
+++ b/fs/afs/file.c
@@ -14,6 +14,7 @@
#include <linux/gfp.h>
#include <linux/task_io_accounting_ops.h>
#include <linux/mm.h>
+#include <linux/netfs.h>
#include "internal.h"

static int afs_file_mmap(struct file *file, struct vm_area_struct *vma);
@@ -22,8 +23,7 @@ static void afs_invalidatepage(struct page *page, unsigned int offset,
unsigned int length);
static int afs_releasepage(struct page *page, gfp_t gfp_flags);

-static int afs_readpages(struct file *filp, struct address_space *mapping,
- struct list_head *pages, unsigned nr_pages);
+static void afs_readahead(struct readahead_control *ractl);

const struct file_operations afs_file_operations = {
.open = afs_open,
@@ -47,7 +47,7 @@ const struct inode_operations afs_file_inode_operations = {

const struct address_space_operations afs_fs_aops = {
.readpage = afs_readpage,
- .readpages = afs_readpages,
+ .readahead = afs_readahead,
.set_page_dirty = afs_set_page_dirty,
.launder_page = afs_launder_page,
.releasepage = afs_releasepage,
@@ -184,61 +184,17 @@ int afs_release(struct inode *inode, struct file *file)
}

/*
- * Handle completion of a read operation.
+ * Allocate a new read record.
*/
-static void afs_file_read_done(struct afs_read *req)
+struct afs_read *afs_alloc_read(gfp_t gfp)
{
- struct afs_vnode *vnode = req->vnode;
- struct page *page;
- pgoff_t index = req->pos >> PAGE_SHIFT;
- pgoff_t last = index + req->nr_pages - 1;
-
- XA_STATE(xas, &vnode->vfs_inode.i_mapping->i_pages, index);
-
- if (iov_iter_count(req->iter) > 0) {
- /* The read was short - clear the excess buffer. */
- _debug("afterclear %zx %zx %llx/%llx",
- req->iter->iov_offset,
- iov_iter_count(req->iter),
- req->actual_len, req->len);
- iov_iter_zero(iov_iter_count(req->iter), req->iter);
- }
-
- rcu_read_lock();
- xas_for_each(&xas, page, last) {
- page_endio(page, false, 0);
- put_page(page);
- }
- rcu_read_unlock();
-
- task_io_account_read(req->len);
- req->cleanup = NULL;
-}
-
-/*
- * Dispose of our locks and refs on the pages if the read failed.
- */
-static void afs_file_read_cleanup(struct afs_read *req)
-{
- struct page *page;
- pgoff_t index = req->pos >> PAGE_SHIFT;
- pgoff_t last = index + req->nr_pages - 1;
-
- if (req->iter) {
- XA_STATE(xas, &req->vnode->vfs_inode.i_mapping->i_pages, index);
-
- _enter("%lu,%u,%zu", index, req->nr_pages, iov_iter_count(req->iter));
+ struct afs_read *req;

- rcu_read_lock();
- xas_for_each(&xas, page, last) {
- BUG_ON(xa_is_value(page));
- BUG_ON(PageCompound(page));
+ req = kzalloc(sizeof(struct afs_read), gfp);
+ if (req)
+ refcount_set(&req->usage, 1);

- page_endio(page, false, req->error);
- put_page(page);
- }
- rcu_read_unlock();
- }
+ return req;
}

/*
@@ -257,14 +213,20 @@ void afs_put_read(struct afs_read *req)
static void afs_fetch_data_notify(struct afs_operation *op)
{
struct afs_read *req = op->fetch.req;
+ struct netfs_read_subrequest *subreq = req->subreq;
int error = op->error;

if (error == -ECONNABORTED)
error = afs_abort_to_error(op->ac.abort_code);
req->error = error;

- if (req->done)
+ if (subreq) {
+ __set_bit(NETFS_SREQ_CLEAR_TAIL, &subreq->flags);
+ netfs_subreq_terminated(subreq, error ?: req->actual_len, false);
+ req->subreq = NULL;
+ } else if (req->done) {
req->done(req);
+ }
}

static void afs_fetch_data_success(struct afs_operation *op)
@@ -308,8 +270,11 @@ int afs_fetch_data(struct afs_vnode *vnode, struct afs_read *req)
key_serial(req->key));

op = afs_alloc_operation(req->key, vnode->volume);
- if (IS_ERR(op))
+ if (IS_ERR(op)) {
+ if (req->subreq)
+ netfs_subreq_terminated(req->subreq, PTR_ERR(op), false);
return PTR_ERR(op);
+ }

afs_op_set_vnode(op, 0, vnode);

@@ -318,222 +283,86 @@ int afs_fetch_data(struct afs_vnode *vnode, struct afs_read *req)
return afs_do_sync_operation(op);
}

-/*
- * read page from file, directory or symlink, given a key to use
- */
-static int afs_page_filler(struct key *key, struct page *page)
+static void afs_req_issue_op(struct netfs_read_subrequest *subreq)
{
- struct inode *inode = page->mapping->host;
- struct afs_vnode *vnode = AFS_FS_I(inode);
- struct afs_read *req;
- int ret;
-
- _enter("{%x},{%lu},{%lu}", key_serial(key), inode->i_ino, page->index);
+ struct afs_vnode *vnode = AFS_FS_I(subreq->rreq->inode);
+ struct afs_read *fsreq;

- BUG_ON(!PageLocked(page));
-
- ret = -ESTALE;
- if (test_bit(AFS_VNODE_DELETED, &vnode->flags))
- goto error;
+ fsreq = afs_alloc_read(GFP_NOFS);
+ if (!fsreq)
+ return netfs_subreq_terminated(subreq, -ENOMEM, false);

- req = kzalloc(sizeof(struct afs_read), GFP_KERNEL);
- if (!req)
- goto enomem;
-
- refcount_set(&req->usage, 1);
- req->vnode = vnode;
- req->key = key_get(key);
- req->pos = (loff_t)page->index << PAGE_SHIFT;
- req->len = thp_size(page);
- req->nr_pages = thp_nr_pages(page);
- req->done = afs_file_read_done;
- req->cleanup = afs_file_read_cleanup;
-
- get_page(page);
- iov_iter_xarray(&req->def_iter, READ, &page->mapping->i_pages,
- req->pos, req->len);
- req->iter = &req->def_iter;
-
- ret = afs_fetch_data(vnode, req);
- if (ret < 0)
- goto fetch_error;
+ fsreq->subreq = subreq;
+ fsreq->pos = subreq->start + subreq->transferred;
+ fsreq->len = subreq->len - subreq->transferred;
+ fsreq->key = subreq->rreq->netfs_priv;
+ fsreq->vnode = vnode;
+ fsreq->iter = &fsreq->def_iter;

- afs_put_read(req);
- _leave(" = 0");
- return 0;
+ iov_iter_xarray(&fsreq->def_iter, READ,
+ &fsreq->vnode->vfs_inode.i_mapping->i_pages,
+ fsreq->pos, fsreq->len);

-fetch_error:
- switch (ret) {
- case -EINTR:
- case -ENOMEM:
- case -ERESTARTSYS:
- case -EAGAIN:
- afs_put_read(req);
- goto error;
- case -ENOENT:
- _debug("got NOENT from server - marking file deleted and stale");
- set_bit(AFS_VNODE_DELETED, &vnode->flags);
- ret = -ESTALE;
- /* Fall through */
- default:
- page_endio(page, false, ret);
- afs_put_read(req);
- _leave(" = %d", ret);
- return ret;
- }
-
-enomem:
- ret = -ENOMEM;
-error:
- unlock_page(page);
- _leave(" = %d", ret);
- return ret;
+ afs_fetch_data(fsreq->vnode, fsreq);
}

-/*
- * read page from file, directory or symlink, given a file to nominate the key
- * to be used
- */
-static int afs_readpage(struct file *file, struct page *page)
+static int afs_symlink_readpage(struct page *page)
{
- struct key *key;
+ struct afs_vnode *vnode = AFS_FS_I(page->mapping->host);
+ struct afs_read *fsreq;
int ret;

- if (file) {
- key = afs_file_key(file);
- ASSERT(key != NULL);
- ret = afs_page_filler(key, page);
- } else {
- struct inode *inode = page->mapping->host;
- key = afs_request_key(AFS_FS_S(inode->i_sb)->cell);
- if (IS_ERR(key)) {
- ret = PTR_ERR(key);
- } else {
- ret = afs_page_filler(key, page);
- key_put(key);
- }
- }
- return ret;
-}
-
-/*
- * Read a contiguous set of pages.
- */
-static int afs_readpages_one(struct file *file, struct address_space *mapping,
- struct list_head *pages)
-{
- struct afs_vnode *vnode = AFS_FS_I(mapping->host);
- struct afs_read *req;
- struct list_head *p;
- struct page *first, *page;
- pgoff_t index;
- int ret, n;
-
- /* Count the number of contiguous pages at the front of the list. Note
- * that the list goes prev-wards rather than next-wards.
- */
- first = lru_to_page(pages);
- index = first->index + 1;
- n = 1;
- for (p = first->lru.prev; p != pages; p = p->prev) {
- page = list_entry(p, struct page, lru);
- if (page->index != index)
- break;
- index++;
- n++;
- }
-
- req = kzalloc(sizeof(struct afs_read), GFP_NOFS);
- if (!req)
+ fsreq = afs_alloc_read(GFP_NOFS);
+ if (!fsreq)
return -ENOMEM;

- refcount_set(&req->usage, 1);
- req->vnode = vnode;
- req->key = key_get(afs_file_key(file));
- req->done = afs_file_read_done;
- req->cleanup = afs_file_read_cleanup;
- req->pos = first->index;
- req->pos <<= PAGE_SHIFT;
-
- /* Add pages to the LRU until it fails. We keep the pages ref'd and
- * locked until the read is complete.
- *
- * Note that it's possible for the file size to change whilst we're
- * doing this, but we rely on the server returning less than we asked
- * for if the file shrank. We also rely on this to deal with a partial
- * page at the end of the file.
- */
- do {
- page = lru_to_page(pages);
- list_del(&page->lru);
- index = page->index;
- if (add_to_page_cache_lru(page, mapping, index,
- readahead_gfp_mask(mapping))) {
- put_page(page);
- break;
- }
-
- req->nr_pages++;
- } while (req->nr_pages < n);
-
- if (req->nr_pages == 0) {
- afs_put_read(req);
- return 0;
- }
-
- req->len = req->nr_pages * PAGE_SIZE;
- iov_iter_xarray(&req->def_iter, READ, &file->f_mapping->i_pages,
- req->pos, req->len);
- req->iter = &req->def_iter;
+ fsreq->pos = page->index * PAGE_SIZE;
+ fsreq->len = PAGE_SIZE;
+ fsreq->vnode = vnode;
+ fsreq->iter = &fsreq->def_iter;
+ iov_iter_xarray(&fsreq->def_iter, READ, &page->mapping->i_pages,
+ fsreq->pos, fsreq->len);

- ret = afs_fetch_data(vnode, req);
- if (ret < 0)
- goto error;
+ ret = afs_fetch_data(fsreq->vnode, fsreq);
+ page_endio(page, false, ret);
+ return ret;
+}

- afs_put_read(req);
- return 0;
+static void afs_init_rreq(struct netfs_read_request *rreq, struct file *file)
+{
+ rreq->netfs_priv = key_get(afs_file_key(file));
+}

-error:
- if (ret == -ENOENT) {
- _debug("got NOENT from server - marking file deleted and stale");
- set_bit(AFS_VNODE_DELETED, &vnode->flags);
- ret = -ESTALE;
- }
+static int afs_begin_cache_operation(struct netfs_read_request *rreq)
+{
+ struct afs_vnode *vnode = AFS_FS_I(rreq->inode);

- afs_put_read(req);
- return ret;
+ return fscache_begin_read_operation(rreq, afs_vnode_cache(vnode));
}

-/*
- * read a set of pages
- */
-static int afs_readpages(struct file *file, struct address_space *mapping,
- struct list_head *pages, unsigned nr_pages)
+static void afs_priv_cleanup(struct address_space *mapping, void *netfs_priv)
{
- struct key *key = afs_file_key(file);
- struct afs_vnode *vnode;
- int ret = 0;
-
- _enter("{%d},{%lu},,%d",
- key_serial(key), mapping->host->i_ino, nr_pages);
+ key_put(netfs_priv);
+}

- ASSERT(key != NULL);
+static const struct netfs_read_request_ops afs_req_ops = {
+ .init_rreq = afs_init_rreq,
+ .begin_cache_operation = afs_begin_cache_operation,
+ .issue_op = afs_req_issue_op,
+ .cleanup = afs_priv_cleanup,
+};

- vnode = AFS_FS_I(mapping->host);
- if (test_bit(AFS_VNODE_DELETED, &vnode->flags)) {
- _leave(" = -ESTALE");
- return -ESTALE;
- }
+static int afs_readpage(struct file *file, struct page *page)
+{
+ if (!file)
+ return afs_symlink_readpage(page);

- /* attempt to read as many of the pages as possible */
- while (!list_empty(pages)) {
- ret = afs_readpages_one(file, mapping, pages);
- if (ret < 0)
- break;
- }
+ return netfs_readpage(file, page, &afs_req_ops, NULL);
+}

- _leave(" = %d [netting]", ret);
- return ret;
+static void afs_readahead(struct readahead_control *ractl)
+{
+ netfs_readahead(ractl, &afs_req_ops, NULL);
}

/*
diff --git a/fs/afs/fsclient.c b/fs/afs/fsclient.c
index 5e34f4dbd385..2f695a260442 100644
--- a/fs/afs/fsclient.c
+++ b/fs/afs/fsclient.c
@@ -10,6 +10,7 @@
#include <linux/sched.h>
#include <linux/circ_buf.h>
#include <linux/iversion.h>
+#include <linux/netfs.h>
#include "internal.h"
#include "afs_fs.h"
#include "xdr_fs.h"
diff --git a/fs/afs/internal.h b/fs/afs/internal.h
index ee283e3ebc4d..f9a692fc08f4 100644
--- a/fs/afs/internal.h
+++ b/fs/afs/internal.h
@@ -14,6 +14,7 @@
#include <linux/key.h>
#include <linux/workqueue.h>
#include <linux/sched.h>
+#define FSCACHE_USE_NEW_IO_API
#include <linux/fscache.h>
#include <linux/backing-dev.h>
#include <linux/uuid.h>
@@ -207,6 +208,7 @@ struct afs_read {
loff_t file_size; /* File size returned by server */
struct key *key; /* The key to use to reissue the read */
struct afs_vnode *vnode; /* The file being read into. */
+ struct netfs_read_subrequest *subreq; /* Fscache helper read request this belongs to */
afs_dataversion_t data_version; /* Version number returned by server */
refcount_t usage;
unsigned int call_debug_id;
@@ -1049,6 +1051,7 @@ extern void afs_put_wb_key(struct afs_wb_key *);
extern int afs_open(struct inode *, struct file *);
extern int afs_release(struct inode *, struct file *);
extern int afs_fetch_data(struct afs_vnode *, struct afs_read *);
+extern struct afs_read *afs_alloc_read(gfp_t);
extern void afs_put_read(struct afs_read *);

static inline struct afs_read *afs_get_read(struct afs_read *req)
diff --git a/fs/afs/write.c b/fs/afs/write.c
index 099c7dad09c5..bc84c771b0fd 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -930,7 +930,7 @@ vm_fault_t afs_page_mkwrite(struct vm_fault *vmf)
*/
#ifdef CONFIG_AFS_FSCACHE
if (PageFsCache(page) &&
- wait_on_page_bit_killable(page, PG_fscache) < 0)
+ wait_on_page_fscache_killable(page) < 0)
return VM_FAULT_RETRY;
#endif

@@ -944,7 +944,10 @@ vm_fault_t afs_page_mkwrite(struct vm_fault *vmf)
* details the portion of the page we need to write back and we might
* need to redirty the page if there's a problem.
*/
- wait_on_page_writeback(page);
+ if (wait_on_page_writeback_killable(page) < 0) {
+ unlock_page(page);
+ return VM_FAULT_RETRY;
+ }

priv = afs_page_dirty(page, 0, thp_size(page));
priv = afs_page_dirty_mmapped(priv);