fuse: fix premature writetrhough request for large folio

When large folio is enabled and the initial folio offset exceeds
PAGE_SIZE, e.g. the position resides in the second page of a large
folio, after the folio copying the offset (in the page) won't be updated
to 0 even though the expected range is successfully copied until the end
of the folio.  In this case fuse_fill_write_pages() exits prematurelly
before the request has reached the max_write/max_pages limit.

Fix this by eliminating page offset entirely and use folio offset
instead.

Fixes: d60a6015e1a2 ("fuse: support large folios for writethrough writes")
Reviewed-by: Horst Birthelmer <hbirthelmer@ddn.com>
Reviewed-by: Joanne Koong <joannelkoong@gmail.com>
Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

diff --git a/fs/fuse/file.c b/fs/fuse/file.c
index 30a74f61caf00b1a040e17e8676b0350c4876866..c61d80e0a70dc7dd845c666ac0b7fe10a5cfe721 100644 (file)
--- a/fs/fuse/file.c
+++ b/fs/fuse/file.c
@@ -1248,7 +1248,6 @@ static ssize_t fuse_fill_write_pages(struct fuse_io_args *ia,
 {
        struct fuse_args_pages *ap = &ia->ap;
        struct fuse_conn *fc = get_fuse_conn(mapping->host);
-       unsigned offset = pos & (PAGE_SIZE - 1);
        size_t count = 0;
        unsigned int num;
        int err = 0;
@@ -1275,7 +1274,7 @@ static ssize_t fuse_fill_write_pages(struct fuse_io_args *ia,
                if (mapping_writably_mapped(mapping))
                        flush_dcache_folio(folio);
 
-               folio_offset = ((index - folio->index) << PAGE_SHIFT) + offset;
+               folio_offset = offset_in_folio(folio, pos);
                bytes = min(folio_size(folio) - folio_offset, num);
 
                tmp = copy_folio_from_iter_atomic(folio, folio_offset, bytes, ii);
@@ -1305,9 +1304,6 @@ static ssize_t fuse_fill_write_pages(struct fuse_io_args *ia,
                count += tmp;
                pos += tmp;
                num -= tmp;
-               offset += tmp;
-               if (offset == folio_size(folio))
-                       offset = 0;
 
                /* If we copied full folio, mark it uptodate */
                if (tmp == folio_size(folio))
@@ -1319,7 +1315,9 @@ static ssize_t fuse_fill_write_pages(struct fuse_io_args *ia,
                        ia->write.folio_locked = true;
                        break;
                }
-               if (!fc->big_writes || offset != 0)
+               if (!fc->big_writes)
+                       break;
+               if (folio_offset + tmp != folio_size(folio))
                        break;
        }