[PATCH v3 06/19] netfs: Fix read-gaps to remove netfs_folio from filled folio

[David Howells <dhowells@redhat.com>]

Fix netfs_read_gaps() to remove the netfs_folio record from the folio
record before marking the folio uptodate if it successfully fills the gaps
around the dirty data in a streaming write folio (dirty, but not uptodate).

Found with:

    fsx -q -N 1000000 -p 10000 -o 128000 -l 600000 \
        /xfstest.test/junk --replay-ops=junk.fsxops

using the following as junk.fsxops:

    truncate 0x0 0x138b1 0x8b15d *
    write 0x507ee 0x10df7 0x927c0
    write 0x19993 0x10e04 0x927c0 *
    mapwrite 0x66214 0x1a253 0x927c0
    copy_range 0xb704 0x89b9 0x24429 0x79380
    write 0x2402b 0x144a2 0x90660 *
    mapwrite 0x204d5 0x140a0 0x927c0 *
    copy_range 0x1f72c 0x137d0 0x7a906 0x927c0 *
    read 0 0x9157c 0x9157c

on cifs with the default cache option.

It shows folio 0x24 misbehaving if the FMODE_READ check is commented out in
netfs_perform_write():

                if (//(file->f_mode & FMODE_READ) ||
                    netfs_is_cache_enabled(ctx)) {

and no fscache.  This was initially found with the generic/522 xfstest.

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Paulo Alcantara <pc@manguebit.org>
cc: Matthew Wilcox <willy@infradead.org>
cc: netfs@lists.linux.dev
cc: linux-fsdevel@vger.kernel.org
Fixes: ee4cdf7ba857 ("netfs: Speed up buffered reading")
---
 fs/netfs/buffered_read.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/fs/netfs/buffered_read.c b/fs/netfs/buffered_read.c
index a8c0d86118c5..e87a55bda8c5 100644
--- a/fs/netfs/buffered_read.c
+++ b/fs/netfs/buffered_read.c
@@ -397,6 +397,7 @@ static int netfs_read_gaps(struct file *file, struct folio *folio)
 {
 	struct netfs_io_request *rreq;
 	struct address_space *mapping = folio->mapping;
+	struct netfs_group *group = netfs_folio_group(folio);
 	struct netfs_folio *finfo = netfs_folio_info(folio);
 	struct netfs_inode *ctx = netfs_inode(mapping->host);
 	struct folio *sink = NULL;
@@ -463,6 +464,12 @@ static int netfs_read_gaps(struct file *file, struct folio *folio)
 
 	ret = netfs_wait_for_read(rreq);
 	if (ret >= 0) {
+		if (group)
+			folio_change_private(folio, group);
+		else
+			folio_detach_private(folio);
+		kfree(finfo);
+		trace_netfs_folio(folio, netfs_folio_trace_filled_gaps);
 		flush_dcache_folio(folio);
 		folio_mark_uptodate(folio);
 	}
@@ -498,10 +505,8 @@ int netfs_read_folio(struct file *file, struct folio *folio)
 	struct netfs_inode *ctx = netfs_inode(mapping->host);
 	int ret;
 
-	if (folio_test_dirty(folio)) {
-		trace_netfs_folio(folio, netfs_folio_trace_read_gaps);
+	if (folio_test_dirty(folio))
 		return netfs_read_gaps(file, folio);
-	}
 
 	_enter("%lx", folio->index);