From dd05add7b2b6004c5fa3a1f276f56d8668f86b65 Mon Sep 17 00:00:00 2001 From: Paulo Alcantara Date: Sat, 26 Sep 2026 19:20:30 -0300 Subject: netfs: zero the tail of a short DIO/unbuffered read 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 --- tools/testing/vsock/timeout.c | 78 +++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 78 insertions(+) create mode 100644 tools/testing/vsock/timeout.c (limited to 'tools/testing/vsock/timeout.c') diff --git a/tools/testing/vsock/timeout.c b/tools/testing/vsock/timeout.c new file mode 100644 index 000000000..1453d38e0 --- /dev/null +++ b/tools/testing/vsock/timeout.c @@ -0,0 +1,78 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* Timeout API for single-threaded programs that use blocking + * syscalls (read/write/send/recv/connect/accept). + * + * Copyright (C) 2017 Red Hat, Inc. + * + * Author: Stefan Hajnoczi + */ + +/* Use the following pattern: + * + * timeout_begin(TIMEOUT); + * do { + * ret = accept(...); + * timeout_check("accept"); + * } while (ret < 0 && ret == EINTR); + * timeout_end(); + */ + +#include +#include +#include +#include +#include +#include "timeout.h" + +static volatile bool timeout; + +/* SIGALRM handler function. Do not use sleep(2), alarm(2), or + * setitimer(2) while using this API - they may interfere with each + * other. + * + * If you need to sleep, please use timeout_sleep() provided by this API. + */ +void sigalrm(int signo) +{ + timeout = true; +} + +/* Start a timeout. Call timeout_check() to verify that the timeout hasn't + * expired. timeout_end() must be called to stop the timeout. Timeouts cannot + * be nested. + */ +void timeout_begin(unsigned int seconds) +{ + alarm(seconds); +} + +/* Exit with an error message if the timeout has expired */ +void timeout_check(const char *operation) +{ + if (timeout) { + fprintf(stderr, "%s timed out\n", operation); + exit(EXIT_FAILURE); + } +} + +/* Stop a timeout */ +void timeout_end(void) +{ + alarm(0); + timeout = false; +} + +/* Sleep in a timeout section. + * + * nanosleep(2) can be used with this API since POSIX.1 explicitly + * specifies that it does not interact with signals. + */ +int timeout_usleep(useconds_t usec) +{ + struct timespec ts = { + .tv_sec = usec / 1000000, + .tv_nsec = (usec % 1000000) * 1000, + }; + + return nanosleep(&ts, NULL); +} -- cgit v1.3.1