6.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Paulo Alcantara [ Upstream commit dd05add7b2b6004c5fa3a1f276f56d8668f86b65 ] The buffered read collector zero-fills the tail of a short read that stops below the inode's i_size (netfs_clear_unread()), so a read that races an extending write still returns the expected number of bytes. The non-buffered collector path does no such thing: it just records how much was transferred. Add the same zero-fill for the non-buffered case, gated on NETFS_SREQ_CLEAR_TAIL: a subreq's source sets that flag when a short result from it is known to be safe to treat as a hole, as opposed to NETFS_SREQ_HIT_EOF, which means the read genuinely ran off the end of the file and should be reported short as-is. Only CLEAR_TAIL should zero-fill here; a real EOF must stay a real short read. No source currently sets CLEAR_TAIL on an unbuffered/DIO subrequest, so this is inert on its own -- a following change teaches cifs to set it in the one case that needs it. Fixes: e2d46f2ec332 ("netfs: Change the read result collector to only use one work item") Reviewed-by: David Howells Reviewed-by: Namjae Jeon Signed-off-by: Paulo Alcantara Cc: Christian Brauner Cc: Matthew Wilcox Cc: Ronnie Sahlberg Cc: Shyam Prasad N Cc: Tom Talpey Cc: Bharath SM Cc: stable@vger.kernel.org [ sashal: Replaced uoff_t with unsigned long long. ] Signed-off-by: Sasha Levin --- fs/netfs/read_collect.c | 24 ++++++++++++++++++++++++ 1 file changed, 24 insertions(+) diff --git a/fs/netfs/read_collect.c b/fs/netfs/read_collect.c index 4c7312a4c8597..8ad06678e6883 100644 --- a/fs/netfs/read_collect.c +++ b/fs/netfs/read_collect.c @@ -34,6 +34,22 @@ static void netfs_clear_unread(struct netfs_io_subrequest *subreq) __set_bit(NETFS_SREQ_HIT_EOF, &subreq->flags); } +static void netfs_clear_unread_dio(struct netfs_io_subrequest *subreq) +{ + unsigned long long pos = subreq->start + subreq->transferred; + struct netfs_io_request *rreq = subreq->rreq; + size_t fill; + + if (pos >= rreq->i_size) + return; + + fill = min_t(unsigned long long, rreq->i_size - pos, + subreq->len - subreq->transferred); + + netfs_reset_iter(subreq); + subreq->transferred += iov_iter_zero(fill, &subreq->io_iter); +} + /* * Flush, mark and unlock a folio that's now completely read. If we want to * cache the folio, we set the group to NETFS_FOLIO_COPY_TO_CACHE, mark it @@ -259,6 +275,14 @@ static void netfs_collect_read_results(struct netfs_io_request *rreq) test_bit(NETFS_SREQ_HIT_EOF, &front->flags)) netfs_read_unlock_folios(rreq, ¬es); } else { + if (!(notes & HIT_PENDING) && + front->error == 0 && + transferred < front->len && + test_bit(NETFS_SREQ_CLEAR_TAIL, &front->flags)) { + netfs_clear_unread_dio(front); + transferred = front->transferred; + trace_netfs_sreq(front, netfs_sreq_trace_clear); + } stream->collected_to = front->start + transferred; rreq->collected_to = stream->collected_to; } -- 2.53.0