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Message-ID: <aN683ZHUzA5qPVaJ@li-dc0c254c-257c-11b2-a85c-98b6c1322444.ibm.com>
Date: Thu, 2 Oct 2025 23:26:45 +0530
From: Ojaswin Mujoo <ojaswin@...ux.ibm.com>
To: Zorro Lang <zlang@...hat.com>
Cc: fstests@...r.kernel.org, Ritesh Harjani <ritesh.list@...il.com>,
djwong@...nel.org, john.g.garry@...cle.com, tytso@....edu,
linux-xfs@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-ext4@...r.kernel.org
Subject: Re: [PATCH v7 04/12] ltp/fsx.c: Add atomic writes support to fsx
On Sun, Sep 28, 2025 at 09:19:24PM +0800, Zorro Lang wrote:
> On Fri, Sep 19, 2025 at 12:17:57PM +0530, Ojaswin Mujoo wrote:
> > Implement atomic write support to help fuzz atomic writes
> > with fsx.
> >
> > Suggested-by: Ritesh Harjani (IBM) <ritesh.list@...il.com>
> > Reviewed-by: Darrick J. Wong <djwong@...nel.org>
> > Reviewed-by: John Garry <john.g.garry@...cle.com>
> > Signed-off-by: Ojaswin Mujoo <ojaswin@...ux.ibm.com>
> > ---
>
> Hmm... this patch causes more regular fsx test cases fail on old kernel,
> (e.g. g/760, g/617, g/263 ...) except set "FSX_AVOID=-a". Is there a way
> to disable "atomic write" automatically if it's not supported by current
> system?
Hi Zorro,
Sorry for being late, I've been on vacation this week.
Yes so by design we should be automatically disabling atomic writes when
they are not supported by the stack but seems like the issue is that
when we do disable it we print some extra messages to stdout/err which
show up in the xfstests output causing failure.
I can think of 2 ways around this:
1. Don't print anything and just silently drop atomic writes if stack
doesn't support them.
2. Make atomic writes as a default off instead of default on feature but
his loses a bit of coverage as existing tests wont get atomic write
testing free of cost any more.
Regards,
ojaswin
> Thanks,
> Zorro
>
> > ltp/fsx.c | 115 +++++++++++++++++++++++++++++++++++++++++++++++++++---
> > 1 file changed, 110 insertions(+), 5 deletions(-)
> >
> > diff --git a/ltp/fsx.c b/ltp/fsx.c
> > index 163b9453..bdb87ca9 100644
> > --- a/ltp/fsx.c
> > +++ b/ltp/fsx.c
> > @@ -40,6 +40,7 @@
> > #include <liburing.h>
> > #endif
> > #include <sys/syscall.h>
> > +#include "statx.h"
> >
> > #ifndef MAP_FILE
> > # define MAP_FILE 0
> > @@ -49,6 +50,10 @@
> > #define RWF_DONTCACHE 0x80
> > #endif
> >
> > +#ifndef RWF_ATOMIC
> > +#define RWF_ATOMIC 0x40
> > +#endif
> > +
> > #define NUMPRINTCOLUMNS 32 /* # columns of data to print on each line */
> >
> > /* Operation flags (bitmask) */
> > @@ -110,6 +115,7 @@ enum {
> > OP_READ_DONTCACHE,
> > OP_WRITE,
> > OP_WRITE_DONTCACHE,
> > + OP_WRITE_ATOMIC,
> > OP_MAPREAD,
> > OP_MAPWRITE,
> > OP_MAX_LITE,
> > @@ -200,6 +206,11 @@ int uring = 0;
> > int mark_nr = 0;
> > int dontcache_io = 1;
> > int hugepages = 0; /* -h flag */
> > +int do_atomic_writes = 1; /* -a flag disables */
> > +
> > +/* User for atomic writes */
> > +int awu_min = 0;
> > +int awu_max = 0;
> >
> > /* Stores info needed to periodically collapse hugepages */
> > struct hugepages_collapse_info {
> > @@ -288,6 +299,7 @@ static const char *op_names[] = {
> > [OP_READ_DONTCACHE] = "read_dontcache",
> > [OP_WRITE] = "write",
> > [OP_WRITE_DONTCACHE] = "write_dontcache",
> > + [OP_WRITE_ATOMIC] = "write_atomic",
> > [OP_MAPREAD] = "mapread",
> > [OP_MAPWRITE] = "mapwrite",
> > [OP_TRUNCATE] = "truncate",
> > @@ -422,6 +434,7 @@ logdump(void)
> > prt("\t***RRRR***");
> > break;
> > case OP_WRITE_DONTCACHE:
> > + case OP_WRITE_ATOMIC:
> > case OP_WRITE:
> > prt("WRITE 0x%x thru 0x%x\t(0x%x bytes)",
> > lp->args[0], lp->args[0] + lp->args[1] - 1,
> > @@ -1073,6 +1086,25 @@ update_file_size(unsigned offset, unsigned size)
> > file_size = offset + size;
> > }
> >
> > +static int is_power_of_2(unsigned n) {
> > + return ((n & (n - 1)) == 0);
> > +}
> > +
> > +/*
> > + * Round down n to nearest power of 2.
> > + * If n is already a power of 2, return n;
> > + */
> > +static int rounddown_pow_of_2(int n) {
> > + int i = 0;
> > +
> > + if (is_power_of_2(n))
> > + return n;
> > +
> > + for (; (1 << i) < n; i++);
> > +
> > + return 1 << (i - 1);
> > +}
> > +
> > void
> > dowrite(unsigned offset, unsigned size, int flags)
> > {
> > @@ -1081,6 +1113,27 @@ dowrite(unsigned offset, unsigned size, int flags)
> > offset -= offset % writebdy;
> > if (o_direct)
> > size -= size % writebdy;
> > + if (flags & RWF_ATOMIC) {
> > + /* atomic write len must be between awu_min and awu_max */
> > + if (size < awu_min)
> > + size = awu_min;
> > + if (size > awu_max)
> > + size = awu_max;
> > +
> > + /* atomic writes need power-of-2 sizes */
> > + size = rounddown_pow_of_2(size);
> > +
> > + /* atomic writes need naturally aligned offsets */
> > + offset -= offset % size;
> > +
> > + /* Skip the write if we are crossing max filesize */
> > + if ((offset + size) > maxfilelen) {
> > + if (!quiet && testcalls > simulatedopcount)
> > + prt("skipping atomic write past maxfilelen\n");
> > + log4(OP_WRITE_ATOMIC, offset, size, FL_SKIPPED);
> > + return;
> > + }
> > + }
> > if (size == 0) {
> > if (!quiet && testcalls > simulatedopcount && !o_direct)
> > prt("skipping zero size write\n");
> > @@ -1088,7 +1141,10 @@ dowrite(unsigned offset, unsigned size, int flags)
> > return;
> > }
> >
> > - log4(OP_WRITE, offset, size, FL_NONE);
> > + if (flags & RWF_ATOMIC)
> > + log4(OP_WRITE_ATOMIC, offset, size, FL_NONE);
> > + else
> > + log4(OP_WRITE, offset, size, FL_NONE);
> >
> > gendata(original_buf, good_buf, offset, size);
> > if (offset + size > file_size) {
> > @@ -1108,8 +1164,9 @@ dowrite(unsigned offset, unsigned size, int flags)
> > (monitorstart == -1 ||
> > (offset + size > monitorstart &&
> > (monitorend == -1 || offset <= monitorend))))))
> > - prt("%lld write\t0x%x thru\t0x%x\t(0x%x bytes)\tdontcache=%d\n", testcalls,
> > - offset, offset + size - 1, size, (flags & RWF_DONTCACHE) != 0);
> > + prt("%lld write\t0x%x thru\t0x%x\t(0x%x bytes)\tdontcache=%d atomic_wr=%d\n", testcalls,
> > + offset, offset + size - 1, size, (flags & RWF_DONTCACHE) != 0,
> > + (flags & RWF_ATOMIC) != 0);
> > iret = fsxwrite(fd, good_buf + offset, size, offset, flags);
> > if (iret != size) {
> > if (iret == -1)
> > @@ -1785,6 +1842,36 @@ do_dedupe_range(unsigned offset, unsigned length, unsigned dest)
> > }
> > #endif
> >
> > +int test_atomic_writes(void) {
> > + int ret;
> > + struct statx stx;
> > +
> > + if (o_direct != O_DIRECT) {
> > + fprintf(stderr, "main: atomic writes need O_DIRECT (-Z), "
> > + "disabling!\n");
> > + return 0;
> > + }
> > +
> > + ret = xfstests_statx(AT_FDCWD, fname, 0, STATX_WRITE_ATOMIC, &stx);
> > + if (ret < 0) {
> > + fprintf(stderr, "main: Statx failed with %d."
> > + " Failed to determine atomic write limits, "
> > + " disabling!\n", ret);
> > + return 0;
> > + }
> > +
> > + if (stx.stx_attributes & STATX_ATTR_WRITE_ATOMIC &&
> > + stx.stx_atomic_write_unit_min > 0) {
> > + awu_min = stx.stx_atomic_write_unit_min;
> > + awu_max = stx.stx_atomic_write_unit_max;
> > + return 1;
> > + }
> > +
> > + fprintf(stderr, "main: IO Stack does not support "
> > + "atomic writes, disabling!\n");
> > + return 0;
> > +}
> > +
> > #ifdef HAVE_COPY_FILE_RANGE
> > int
> > test_copy_range(void)
> > @@ -2356,6 +2443,12 @@ have_op:
> > goto out;
> > }
> > break;
> > + case OP_WRITE_ATOMIC:
> > + if (!do_atomic_writes) {
> > + log4(OP_WRITE_ATOMIC, offset, size, FL_SKIPPED);
> > + goto out;
> > + }
> > + break;
> > }
> >
> > switch (op) {
> > @@ -2385,6 +2478,11 @@ have_op:
> > dowrite(offset, size, 0);
> > break;
> >
> > + case OP_WRITE_ATOMIC:
> > + TRIM_OFF_LEN(offset, size, maxfilelen);
> > + dowrite(offset, size, RWF_ATOMIC);
> > + break;
> > +
> > case OP_MAPREAD:
> > TRIM_OFF_LEN(offset, size, file_size);
> > domapread(offset, size);
> > @@ -2511,13 +2609,14 @@ void
> > usage(void)
> > {
> > fprintf(stdout, "usage: %s",
> > - "fsx [-dfhknqxyzBEFHIJKLORWXZ0]\n\
> > + "fsx [-adfhknqxyzBEFHIJKLORWXZ0]\n\
> > [-b opnum] [-c Prob] [-g filldata] [-i logdev] [-j logid]\n\
> > [-l flen] [-m start:end] [-o oplen] [-p progressinterval]\n\
> > [-r readbdy] [-s style] [-t truncbdy] [-w writebdy]\n\
> > [-A|-U] [-D startingop] [-N numops] [-P dirpath] [-S seed]\n\
> > [--replay-ops=opsfile] [--record-ops[=opsfile]] [--duration=seconds]\n\
> > ... fname\n\
> > + -a: disable atomic writes\n\
> > -b opnum: beginning operation number (default 1)\n\
> > -c P: 1 in P chance of file close+open at each op (default infinity)\n\
> > -d: debug output for all operations\n\
> > @@ -3059,9 +3158,13 @@ main(int argc, char **argv)
> > setvbuf(stdout, (char *)0, _IOLBF, 0); /* line buffered stdout */
> >
> > while ((ch = getopt_long(argc, argv,
> > - "0b:c:de:fg:hi:j:kl:m:no:p:qr:s:t:uw:xyABD:EFJKHzCILN:OP:RS:UWXZ",
> > + "0ab:c:de:fg:hi:j:kl:m:no:p:qr:s:t:uw:xyABD:EFJKHzCILN:OP:RS:UWXZ",
> > longopts, NULL)) != EOF)
> > switch (ch) {
> > + case 'a':
> > + prt("main(): Atomic writes disabled\n");
> > + do_atomic_writes = 0;
> > + break;
> > case 'b':
> > simulatedopcount = getnum(optarg, &endp);
> > if (!quiet)
> > @@ -3475,6 +3578,8 @@ main(int argc, char **argv)
> > exchange_range_calls = test_exchange_range();
> > if (dontcache_io)
> > dontcache_io = test_dontcache_io();
> > + if (do_atomic_writes)
> > + do_atomic_writes = test_atomic_writes();
> >
> > while (keep_running())
> > if (!test())
> > --
> > 2.49.0
> >
>
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