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nfs: make nfs_page pin-aware

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Modernizing the NFS Direct I/O path to use iov_iter_extract_pages()
introduces page pinning (GUP) instead of standard page referencing.
To handle this correctly, nfs_page must track whether it holds a
pin or a standard reference.

Introduce a new flag, PG_PINNED, to struct nfs_page. Update the creation
path (nfs_page_create_from_page and nfs_page_create_from_folio) to
accept a pinned bool and set the flag accordingly. If the page is pinned,
we skip the existing reference increment (get_page/folio_get) as the pin
itself acts as a reference.

Update nfs_clear_request() & nfs_direct_release_pages() to use
unpin_user_page() or unpin_user_folio() instead of only refcount
decrement (put_page) when PG_PINNED flag is set. Finally, ensure
subrequests inherit the pinning status from their parent request.

Signed-off-by: Pranjal Shrivastava <praan@google.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Anna Schumaker <anna.schumaker@hammerspace.com>
This commit is contained in:
Pranjal Shrivastava 2026-08-14 14:32:51 +00:00 committed by Anna Schumaker
parent a90ee4305c
commit d91ae903f4
5 changed files with 54 additions and 19 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

22
fs/nfs/direct.c
View File

@ -145,11 +145,17 @@ static void nfs_direct_file_adjust_size_locked(struct inode *inode,
}
}
static void nfs_direct_release_pages(struct page **pages, unsigned int npages)
static void nfs_direct_release_pages(struct page **pages, unsigned int npages,
bool pinned)
{
unsigned int i;
for (i = 0; i < npages; i++)
put_page(pages[i]);
if (pinned) {
unpin_user_pages(pages, npages);
} else {
for (i = 0; i < npages; i++)
put_page(pages[i]);
}
}
void nfs_init_cinfo_from_dreq(struct nfs_commit_info *cinfo,
@ -351,7 +357,8 @@ static ssize_t nfs_direct_read_schedule_iovec(struct nfs_direct_req *dreq,
unsigned int req_len = min_t(size_t, bytes, PAGE_SIZE - pgbase);
/* XXX do we need to do the eof zeroing found in async_filler? */
req = nfs_page_create_from_page(dreq->ctx, pagevec[i],
pgbase, pos, req_len);
false, pgbase, pos,
req_len);
if (IS_ERR(req)) {
result = PTR_ERR(req);
break;
@ -366,7 +373,7 @@ static ssize_t nfs_direct_read_schedule_iovec(struct nfs_direct_req *dreq,
requested_bytes += req_len;
pos += req_len;
}
nfs_direct_release_pages(pagevec, npages);
nfs_direct_release_pages(pagevec, npages, false);
kvfree(pagevec);
if (result < 0)
break;
@ -887,7 +894,8 @@ static ssize_t nfs_direct_write_schedule_iovec(struct nfs_direct_req *dreq,
unsigned int req_len = min_t(size_t, bytes, PAGE_SIZE - pgbase);
req = nfs_page_create_from_page(dreq->ctx, pagevec[i],
pgbase, pos, req_len);
false, pgbase, pos,
req_len);
if (IS_ERR(req)) {
result = PTR_ERR(req);
break;
@ -930,7 +938,7 @@ static ssize_t nfs_direct_write_schedule_iovec(struct nfs_direct_req *dreq,
desc.pg_error = 0;
defer = true;
}
nfs_direct_release_pages(pagevec, npages);
nfs_direct_release_pages(pagevec, npages, false);
kvfree(pagevec);
if (result < 0)
break;

44
fs/nfs/pagelist.c
View File

@ -404,20 +404,28 @@ static struct nfs_page *nfs_page_create(struct nfs_lock_context *l_ctx,
return req;
}
static void nfs_page_assign_folio(struct nfs_page *req, struct folio *folio)
static void nfs_page_assign_folio(struct nfs_page *req, struct folio *folio,
bool pinned)
{
if (folio != NULL) {
req->wb_folio = folio;
folio_get(folio);
if (pinned)
set_bit(PG_PINNED, &req->wb_flags);
else
folio_get(folio);
set_bit(PG_FOLIO, &req->wb_flags);
}
}
static void nfs_page_assign_page(struct nfs_page *req, struct page *page)
static void nfs_page_assign_page(struct nfs_page *req, struct page *page,
bool pinned)
{
if (page != NULL) {
req->wb_page = page;
get_page(page);
if (pinned)
set_bit(PG_PINNED, &req->wb_flags);
else
get_page(page);
}
}
@ -425,6 +433,7 @@ static void nfs_page_assign_page(struct nfs_page *req, struct page *page)
* nfs_page_create_from_page - Create an NFS read/write request.
* @ctx: open context to use
* @page: page to write
* @pinned: true if page is pinned
* @pgbase: starting offset within the page for the write
* @offset: file offset for the write
* @count: number of bytes to read/write
@ -435,6 +444,7 @@ static void nfs_page_assign_page(struct nfs_page *req, struct page *page)
*/
struct nfs_page *nfs_page_create_from_page(struct nfs_open_context *ctx,
struct page *page,
bool pinned,
unsigned int pgbase, loff_t offset,
unsigned int count)
{
@ -446,7 +456,7 @@ struct nfs_page *nfs_page_create_from_page(struct nfs_open_context *ctx,
ret = nfs_page_create(l_ctx, pgbase, offset >> PAGE_SHIFT,
offset_in_page(offset), count);
if (!IS_ERR(ret)) {
nfs_page_assign_page(ret, page);
nfs_page_assign_page(ret, page, pinned);
nfs_page_group_init(ret, NULL);
}
nfs_put_lock_context(l_ctx);
@ -457,6 +467,7 @@ struct nfs_page *nfs_page_create_from_page(struct nfs_open_context *ctx,
* nfs_page_create_from_folio - Create an NFS read/write request.
* @ctx: open context to use
* @folio: folio to write
* @pinned: true if folio is pinned
* @offset: starting offset within the folio for the write
* @count: number of bytes to read/write
*
@ -466,6 +477,7 @@ struct nfs_page *nfs_page_create_from_page(struct nfs_open_context *ctx,
*/
struct nfs_page *nfs_page_create_from_folio(struct nfs_open_context *ctx,
struct folio *folio,
bool pinned,
unsigned int offset,
unsigned int count)
{
@ -476,7 +488,7 @@ struct nfs_page *nfs_page_create_from_folio(struct nfs_open_context *ctx,
return ERR_CAST(l_ctx);
ret = nfs_page_create(l_ctx, offset, folio->index, offset, count);
if (!IS_ERR(ret)) {
nfs_page_assign_folio(ret, folio);
nfs_page_assign_folio(ret, folio, pinned);
nfs_page_group_init(ret, NULL);
}
nfs_put_lock_context(l_ctx);
@ -498,9 +510,11 @@ nfs_create_subreq(struct nfs_page *req,
offset, count);
if (!IS_ERR(ret)) {
if (folio)
nfs_page_assign_folio(ret, folio);
nfs_page_assign_folio(ret, folio,
test_bit(PG_PINNED, &req->wb_flags));
else
nfs_page_assign_page(ret, page);
nfs_page_assign_page(ret, page,
test_bit(PG_PINNED, &req->wb_flags));
/* find the last request */
for (last = req->wb_head;
last->wb_this_page != req->wb_head;
@ -552,11 +566,21 @@ static void nfs_clear_request(struct nfs_page *req)
struct nfs_open_context *ctx;
if (folio != NULL) {
folio_put(folio);
if (test_and_clear_bit(PG_PINNED, &req->wb_flags)) {
if (req == req->wb_head)
unpin_user_folio(folio, 1);
} else {
folio_put(folio);
}
req->wb_folio = NULL;
clear_bit(PG_FOLIO, &req->wb_flags);
} else if (page != NULL) {
put_page(page);
if (test_and_clear_bit(PG_PINNED, &req->wb_flags)) {
if (req == req->wb_head)
unpin_user_page(page);
} else {
put_page(page);
}
req->wb_page = NULL;
}
if (l_ctx != NULL) {

2
fs/nfs/read.c
View File

@ -324,7 +324,7 @@ int nfs_read_add_folio(struct nfs_pageio_descriptor *pgio,
aligned_len = min_t(unsigned int, ALIGN(len, rsize), fsize);
new = nfs_page_create_from_folio(ctx, folio, 0, aligned_len);
new = nfs_page_create_from_folio(ctx, folio, false, 0, aligned_len);
if (IS_ERR(new)) {
error = PTR_ERR(new);
if (nfs_netfs_folio_unlock(folio))

2
fs/nfs/write.c
View File

@ -1089,7 +1089,7 @@ static struct nfs_page *nfs_setup_write_request(struct nfs_open_context *ctx,
req = nfs_try_to_update_request(folio, offset, bytes);
if (req != NULL)
goto out;
req = nfs_page_create_from_folio(ctx, folio, offset, bytes);
req = nfs_page_create_from_folio(ctx, folio, false, offset, bytes);
if (IS_ERR(req))
goto out;
nfs_inode_add_request(req);

3
include/linux/nfs_page.h
View File

@ -38,6 +38,7 @@ enum {
PG_REMOVE, /* page group sync bit in write path */
PG_CONTENDED1, /* Is someone waiting for a lock? */
PG_CONTENDED2, /* Is someone waiting for a lock? */
PG_PINNED, /* page is pinned by GUP */
};
struct nfs_inode;
@ -125,11 +126,13 @@ struct nfs_pageio_descriptor {
extern struct nfs_page *nfs_page_create_from_page(struct nfs_open_context *ctx,
struct page *page,
bool pinned,
unsigned int pgbase,
loff_t offset,
unsigned int count);
extern struct nfs_page *nfs_page_create_from_folio(struct nfs_open_context *ctx,
struct folio *folio,
bool pinned,
unsigned int offset,
unsigned int count);
extern void nfs_release_request(struct nfs_page *);