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 --- lib/test_ref_tracker.c | 116 +++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 116 insertions(+) create mode 100644 lib/test_ref_tracker.c (limited to 'lib/test_ref_tracker.c') diff --git a/lib/test_ref_tracker.c b/lib/test_ref_tracker.c new file mode 100644 index 000000000..b983ceb12 --- /dev/null +++ b/lib/test_ref_tracker.c @@ -0,0 +1,116 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Reference tracker self test. + * + * Copyright (c) 2021 Eric Dumazet + */ +#include +#include +#include +#include +#include +#include + +static struct ref_tracker_dir ref_dir; +static struct ref_tracker *tracker[20]; + +#define TRT_ALLOC(X) static noinline void \ + alloctest_ref_tracker_alloc##X(struct ref_tracker_dir *dir, \ + struct ref_tracker **trackerp) \ + { \ + ref_tracker_alloc(dir, trackerp, GFP_KERNEL); \ + } + +TRT_ALLOC(1) +TRT_ALLOC(2) +TRT_ALLOC(3) +TRT_ALLOC(4) +TRT_ALLOC(5) +TRT_ALLOC(6) +TRT_ALLOC(7) +TRT_ALLOC(8) +TRT_ALLOC(9) +TRT_ALLOC(10) +TRT_ALLOC(11) +TRT_ALLOC(12) +TRT_ALLOC(13) +TRT_ALLOC(14) +TRT_ALLOC(15) +TRT_ALLOC(16) +TRT_ALLOC(17) +TRT_ALLOC(18) +TRT_ALLOC(19) + +#undef TRT_ALLOC + +static noinline void +alloctest_ref_tracker_free(struct ref_tracker_dir *dir, + struct ref_tracker **trackerp) +{ + ref_tracker_free(dir, trackerp); +} + + +static struct timer_list test_ref_tracker_timer; +static atomic_t test_ref_timer_done = ATOMIC_INIT(0); + +static void test_ref_tracker_timer_func(struct timer_list *t) +{ + ref_tracker_alloc(&ref_dir, &tracker[0], GFP_ATOMIC); + atomic_set(&test_ref_timer_done, 1); +} + +static int __init test_ref_tracker_init(void) +{ + int i; + + ref_tracker_dir_init(&ref_dir, 100, "selftest"); + + timer_setup(&test_ref_tracker_timer, test_ref_tracker_timer_func, 0); + mod_timer(&test_ref_tracker_timer, jiffies + 1); + + alloctest_ref_tracker_alloc1(&ref_dir, &tracker[1]); + alloctest_ref_tracker_alloc2(&ref_dir, &tracker[2]); + alloctest_ref_tracker_alloc3(&ref_dir, &tracker[3]); + alloctest_ref_tracker_alloc4(&ref_dir, &tracker[4]); + alloctest_ref_tracker_alloc5(&ref_dir, &tracker[5]); + alloctest_ref_tracker_alloc6(&ref_dir, &tracker[6]); + alloctest_ref_tracker_alloc7(&ref_dir, &tracker[7]); + alloctest_ref_tracker_alloc8(&ref_dir, &tracker[8]); + alloctest_ref_tracker_alloc9(&ref_dir, &tracker[9]); + alloctest_ref_tracker_alloc10(&ref_dir, &tracker[10]); + alloctest_ref_tracker_alloc11(&ref_dir, &tracker[11]); + alloctest_ref_tracker_alloc12(&ref_dir, &tracker[12]); + alloctest_ref_tracker_alloc13(&ref_dir, &tracker[13]); + alloctest_ref_tracker_alloc14(&ref_dir, &tracker[14]); + alloctest_ref_tracker_alloc15(&ref_dir, &tracker[15]); + alloctest_ref_tracker_alloc16(&ref_dir, &tracker[16]); + alloctest_ref_tracker_alloc17(&ref_dir, &tracker[17]); + alloctest_ref_tracker_alloc18(&ref_dir, &tracker[18]); + alloctest_ref_tracker_alloc19(&ref_dir, &tracker[19]); + + /* free all trackers but first 0 and 1. */ + for (i = 2; i < ARRAY_SIZE(tracker); i++) + alloctest_ref_tracker_free(&ref_dir, &tracker[i]); + + /* Attempt to free an already freed tracker. */ + alloctest_ref_tracker_free(&ref_dir, &tracker[2]); + + while (!atomic_read(&test_ref_timer_done)) + msleep(1); + + /* This should warn about tracker[0] & tracker[1] being not freed. */ + ref_tracker_dir_exit(&ref_dir); + + return 0; +} + +static void __exit test_ref_tracker_exit(void) +{ +} + +module_init(test_ref_tracker_init); +module_exit(test_ref_tracker_exit); + +MODULE_DESCRIPTION("Reference tracker self test"); +MODULE_LICENSE("GPL v2"); -- cgit v1.3.1