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authorDavid Howells <dhowells@redhat.com>2023-10-02 14:51:19 +0300
committerDavid Howells <dhowells@redhat.com>2023-12-28 12:45:22 +0300
commit7f84a7b9892d1c9429a6f5d6f67916c61b3fc183 (patch)
treee5234e5c233c8f3053ba02050336a2bf04eb7818 /fs
parentc38f4e96e605f17990e871214e6ea1496bc4e65f (diff)
downloadlinux-7f84a7b9892d1c9429a6f5d6f67916c61b3fc183.tar.xz
netfs: Make netfs_read_folio() handle streaming-write pages
netfs_read_folio() needs to handle partially-valid pages that are marked dirty, but not uptodate in the event that someone tries to read a page was used to cache data by a streaming write. In such a case, make netfs_read_folio() set up a bvec iterator that points to the parts of the folio that need filling and to a sink page for the data that should be discarded and use that instead of i_pages as the iterator to be written to. This requires netfs_rreq_unlock_folios() to convert the page into a normal dirty uptodate page, getting rid of the partial write record and bumping the group pointer over to folio->private. Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Jeff Layton <jlayton@kernel.org> cc: linux-cachefs@redhat.com cc: linux-fsdevel@vger.kernel.org cc: linux-mm@kvack.org
Diffstat (limited to 'fs')
-rw-r--r--fs/netfs/buffered_read.c61
1 files changed, 58 insertions, 3 deletions
diff --git a/fs/netfs/buffered_read.c b/fs/netfs/buffered_read.c
index 73a6e4d61f9d..950f63fc156a 100644
--- a/fs/netfs/buffered_read.c
+++ b/fs/netfs/buffered_read.c
@@ -16,6 +16,7 @@
void netfs_rreq_unlock_folios(struct netfs_io_request *rreq)
{
struct netfs_io_subrequest *subreq;
+ struct netfs_folio *finfo;
struct folio *folio;
pgoff_t start_page = rreq->start / PAGE_SIZE;
pgoff_t last_page = ((rreq->start + rreq->len) / PAGE_SIZE) - 1;
@@ -87,6 +88,15 @@ void netfs_rreq_unlock_folios(struct netfs_io_request *rreq)
if (!pg_failed) {
flush_dcache_folio(folio);
+ finfo = netfs_folio_info(folio);
+ if (finfo) {
+ trace_netfs_folio(folio, netfs_folio_trace_filled_gaps);
+ if (finfo->netfs_group)
+ folio_change_private(folio, finfo->netfs_group);
+ else
+ folio_detach_private(folio);
+ kfree(finfo);
+ }
folio_mark_uptodate(folio);
}
@@ -239,6 +249,7 @@ int netfs_read_folio(struct file *file, struct folio *folio)
struct address_space *mapping = folio_file_mapping(folio);
struct netfs_io_request *rreq;
struct netfs_inode *ctx = netfs_inode(mapping->host);
+ struct folio *sink = NULL;
int ret;
_enter("%lx", folio_index(folio));
@@ -259,12 +270,56 @@ int netfs_read_folio(struct file *file, struct folio *folio)
trace_netfs_read(rreq, rreq->start, rreq->len, netfs_read_trace_readpage);
/* Set up the output buffer */
- iov_iter_xarray(&rreq->iter, ITER_DEST, &mapping->i_pages,
- rreq->start, rreq->len);
+ if (folio_test_dirty(folio)) {
+ /* Handle someone trying to read from an unflushed streaming
+ * write. We fiddle the buffer so that a gap at the beginning
+ * and/or a gap at the end get copied to, but the middle is
+ * discarded.
+ */
+ struct netfs_folio *finfo = netfs_folio_info(folio);
+ struct bio_vec *bvec;
+ unsigned int from = finfo->dirty_offset;
+ unsigned int to = from + finfo->dirty_len;
+ unsigned int off = 0, i = 0;
+ size_t flen = folio_size(folio);
+ size_t nr_bvec = flen / PAGE_SIZE + 2;
+ size_t part;
+
+ ret = -ENOMEM;
+ bvec = kmalloc_array(nr_bvec, sizeof(*bvec), GFP_KERNEL);
+ if (!bvec)
+ goto discard;
+
+ sink = folio_alloc(GFP_KERNEL, 0);
+ if (!sink)
+ goto discard;
+
+ trace_netfs_folio(folio, netfs_folio_trace_read_gaps);
+
+ rreq->direct_bv = bvec;
+ rreq->direct_bv_count = nr_bvec;
+ if (from > 0) {
+ bvec_set_folio(&bvec[i++], folio, from, 0);
+ off = from;
+ }
+ while (off < to) {
+ part = min_t(size_t, to - off, PAGE_SIZE);
+ bvec_set_folio(&bvec[i++], sink, part, 0);
+ off += part;
+ }
+ if (to < flen)
+ bvec_set_folio(&bvec[i++], folio, flen - to, to);
+ iov_iter_bvec(&rreq->iter, ITER_DEST, bvec, i, rreq->len);
+ } else {
+ iov_iter_xarray(&rreq->iter, ITER_DEST, &mapping->i_pages,
+ rreq->start, rreq->len);
+ }
ret = netfs_begin_read(rreq, true);
+ if (sink)
+ folio_put(sink);
netfs_put_request(rreq, false, netfs_rreq_trace_put_return);
- return ret;
+ return ret < 0 ? ret : 0;
discard:
netfs_put_request(rreq, false, netfs_rreq_trace_put_discard);