[PATCHSET 0/2] Add RWF_DONTCACHE support

[PATCHSET 0/2] Add RWF_DONTCACHE support

[Jens Axboe]

Hi,

This adds support for RWF_DONTCACHE for fsx and fsstress, which was
used for testing the kernel patchset referenced in the two patches.

-- 
Jens Axboe

[PATCH 1/2] fsstress: add support for RWF_DONTCACHE

[Jens Axboe]

Using RWF_DONTCACHE tells the kernel that any page cache instantiated
by this operation should get pruned once the operation completes. If
data is in cache prior to the operation it will remain there.

Add ops for testing both the read and write side of this. If the kernel
being tested doesn't support RWF_DONTCACHE, then operations are performed
with regular read/write buffered IO.

See the kernel posting adding support:

https://lore.kernel.org/linux-fsdevel/20241220154831.1086649-1-axboe@kernel.dk/

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 ltp/fsstress.c | 136 +++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 136 insertions(+)

diff --git a/ltp/fsstress.c b/ltp/fsstress.c
index 3d248ee25791..df9f6ffb86fc 100644
--- a/ltp/fsstress.c
+++ b/ltp/fsstress.c
@@ -82,6 +82,12 @@ static int renameat2(int dfd1, const char *path1,
 #define RENAME_WHITEOUT		(1 << 2)	/* Whiteout source */
 #endif
 
+#ifndef RWF_DONTCACHE
+#define RWF_DONTCACHE		0x80
+#endif
+
+static int have_rwf_dontcache = 1;
+
 #define FILELEN_MAX		(32*4096)
 
 typedef enum {
@@ -117,6 +123,7 @@ typedef enum {
 	OP_COLLAPSE,
 	OP_INSERT,
 	OP_READ,
+	OP_READ_DONTCACHE,
 	OP_READLINK,
 	OP_READV,
 	OP_REMOVEFATTR,
@@ -143,6 +150,7 @@ typedef enum {
 	OP_URING_READ,
 	OP_URING_WRITE,
 	OP_WRITE,
+	OP_WRITE_DONTCACHE,
 	OP_WRITEV,
 	OP_EXCHANGE_RANGE,
 	OP_LAST
@@ -248,6 +256,7 @@ void	zero_f(opnum_t, long);
 void	collapse_f(opnum_t, long);
 void	insert_f(opnum_t, long);
 void	unshare_f(opnum_t, long);
+void	read_dontcache_f(opnum_t, long);
 void	read_f(opnum_t, long);
 void	readlink_f(opnum_t, long);
 void	readv_f(opnum_t, long);
@@ -273,6 +282,7 @@ void	unlink_f(opnum_t, long);
 void	unresvsp_f(opnum_t, long);
 void	uring_read_f(opnum_t, long);
 void	uring_write_f(opnum_t, long);
+void	write_dontcache_f(opnum_t, long);
 void	write_f(opnum_t, long);
 void	writev_f(opnum_t, long);
 void	exchangerange_f(opnum_t, long);
@@ -315,6 +325,7 @@ struct opdesc	ops[OP_LAST]	= {
 	[OP_COLLAPSE]	   = {"collapse",      collapse_f,	1, 1 },
 	[OP_INSERT]	   = {"insert",	       insert_f,	1, 1 },
 	[OP_READ]	   = {"read",	       read_f,		1, 0 },
+	[OP_READ_DONTCACHE] = {"read_dontcache", read_dontcache_f,	1, 0 },
 	[OP_READLINK]	   = {"readlink",      readlink_f,	1, 0 },
 	[OP_READV]	   = {"readv",	       readv_f,		1, 0 },
 	/* remove (delete) extended attribute */
@@ -346,6 +357,7 @@ struct opdesc	ops[OP_LAST]	= {
 	[OP_URING_WRITE]   = {"uring_write",   uring_write_f,	1, 1 },
 	[OP_WRITE]	   = {"write",	       write_f,		4, 1 },
 	[OP_WRITEV]	   = {"writev",	       writev_f,	4, 1 },
+	[OP_WRITE_DONTCACHE]= {"write_dontcache", write_dontcache_f,4, 1 },
 	[OP_EXCHANGE_RANGE]= {"exchangerange", exchangerange_f,	2, 1 },
 }, *ops_end;
 
@@ -4635,6 +4647,71 @@ readv_f(opnum_t opno, long r)
 	close(fd);
 }
 
+void
+read_dontcache_f(opnum_t opno, long r)
+{
+	int		e;
+	pathname_t	f;
+	int		fd;
+	int64_t		lr;
+	off64_t		off;
+	struct stat64	stb;
+	int		v;
+	char		st[1024];
+	struct iovec	iov;
+	int flags;
+
+	init_pathname(&f);
+	if (!get_fname(FT_REGFILE, r, &f, NULL, NULL, &v)) {
+		if (v)
+			printf("%d/%lld: read - no filename\n", procid, opno);
+		free_pathname(&f);
+		return;
+	}
+	fd = open_path(&f, O_RDONLY);
+	e = fd < 0 ? errno : 0;
+	check_cwd();
+	if (fd < 0) {
+		if (v)
+			printf("%d/%lld: read - open %s failed %d\n",
+				procid, opno, f.path, e);
+		free_pathname(&f);
+		return;
+	}
+	if (fstat64(fd, &stb) < 0) {
+		if (v)
+			printf("%d/%lld: read - fstat64 %s failed %d\n",
+				procid, opno, f.path, errno);
+		free_pathname(&f);
+		close(fd);
+		return;
+	}
+	inode_info(st, sizeof(st), &stb, v);
+	if (stb.st_size == 0) {
+		if (v)
+			printf("%d/%lld: read - %s%s zero size\n", procid, opno,
+			       f.path, st);
+		free_pathname(&f);
+		close(fd);
+		return;
+	}
+	lr = ((int64_t)random() << 32) + random();
+	off = (off64_t)(lr % stb.st_size);
+	iov.iov_len = (random() % FILELEN_MAX) + 1;
+	iov.iov_base = malloc(iov.iov_len);
+	flags = have_rwf_dontcache ? RWF_DONTCACHE : 0;
+	e = preadv2(fd, &iov, 1, off, flags) < 0 ? errno : 0;
+	if (have_rwf_dontcache && e == EOPNOTSUPP)
+		e = preadv2(fd, &iov, 1, off, 0) < 0 ? errno : 0;
+	free(iov.iov_base);
+	if (v)
+		printf("%d/%lld: read dontcache %s%s [%lld,%d] %d\n",
+		       procid, opno, f.path, st, (long long)off,
+		       (int)iov.iov_len, e);
+	free_pathname(&f);
+	close(fd);
+}
+
 void
 removefattr_f(opnum_t opno, long r)
 {
@@ -5509,6 +5586,65 @@ writev_f(opnum_t opno, long r)
 	close(fd);
 }
 
+void
+write_dontcache_f(opnum_t opno, long r)
+{
+	int		e;
+	pathname_t	f;
+	int		fd;
+	int64_t		lr;
+	off64_t		off;
+	struct stat64	stb;
+	int		v;
+	char		st[1024];
+	struct iovec	iov;
+	int flags;
+
+	init_pathname(&f);
+	if (!get_fname(FT_REGm, r, &f, NULL, NULL, &v)) {
+		if (v)
+			printf("%d/%lld: write - no filename\n", procid, opno);
+		free_pathname(&f);
+		return;
+	}
+	fd = open_path(&f, O_WRONLY);
+	e = fd < 0 ? errno : 0;
+	check_cwd();
+	if (fd < 0) {
+		if (v)
+			printf("%d/%lld: write - open %s failed %d\n",
+				procid, opno, f.path, e);
+		free_pathname(&f);
+		return;
+	}
+	if (fstat64(fd, &stb) < 0) {
+		if (v)
+			printf("%d/%lld: write - fstat64 %s failed %d\n",
+				procid, opno, f.path, errno);
+		free_pathname(&f);
+		close(fd);
+		return;
+	}
+	inode_info(st, sizeof(st), &stb, v);
+	lr = ((int64_t)random() << 32) + random();
+	off = (off64_t)(lr % MIN(stb.st_size + (1024 * 1024), MAXFSIZE));
+	off %= maxfsize;
+	iov.iov_len = (random() % FILELEN_MAX) + 1;
+	iov.iov_base = malloc(iov.iov_len);
+	memset(iov.iov_base, nameseq & 0xff, iov.iov_len);
+	flags = have_rwf_dontcache ? RWF_DONTCACHE : 0;
+	e = pwritev2(fd, &iov, 1, off, flags) < 0 ? errno : 0;
+	if (have_rwf_dontcache && e == EOPNOTSUPP)
+		e = pwritev2(fd, &iov, 1, off, 0) < 0 ? errno : 0;
+	free(iov.iov_base);
+	if (v)
+		printf("%d/%lld: write dontcache %s%s [%lld,%d] %d\n",
+		       procid, opno, f.path, st, (long long)off,
+		       (int)iov.iov_len, e);
+	free_pathname(&f);
+	close(fd);
+}
+
 char *
 xattr_flag_to_string(int flag)
 {
-- 
2.47.1

[PATCH 2/2] fsx: add support for RWF_DONTCACHE

[Jens Axboe]

Using RWF_DONTCACHE tells the kernel that any page cache instantiated
by this operation should get pruned once the operation completes. If
data is in cache prior to the operation it will remain there.

Add ops for testing both the read and write side of this. At startup,
kernel support for this feature is probed. If support isn't available,
uncached/dontcache IO is performed as regular buffered IO. If -Z is
used to turn on O_DIRECT, then uncached/dontcache IO isn't performed.
Defaults to on if available, and adds a -T parameter to turn it off.

See the kernel posting adding support:

https://lore.kernel.org/linux-fsdevel/20241220154831.1086649-1-axboe@kernel.dk/

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
 ltp/fsx.c | 115 ++++++++++++++++++++++++++++++++++++------------------
 1 file changed, 77 insertions(+), 38 deletions(-)

diff --git a/ltp/fsx.c b/ltp/fsx.c
index 41933354328a..7c996026157d 100644
--- a/ltp/fsx.c
+++ b/ltp/fsx.c
@@ -43,6 +43,10 @@
 # define MAP_FILE 0
 #endif
 
+#ifndef RWF_DONTCACHE
+#define RWF_DONTCACHE	0x80
+#endif
+
 #define NUMPRINTCOLUMNS 32	/* # columns of data to print on each line */
 
 /* Operation flags (bitmask) */
@@ -101,7 +105,9 @@ int			logcount = 0;	/* total ops */
 enum {
 	/* common operations */
 	OP_READ = 0,
+	OP_READ_DONTCACHE,
 	OP_WRITE,
+	OP_WRITE_DONTCACHE,
 	OP_MAPREAD,
 	OP_MAPWRITE,
 	OP_MAX_LITE,
@@ -190,15 +196,16 @@ int	o_direct;			/* -Z */
 int	aio = 0;
 int	uring = 0;
 int	mark_nr = 0;
+int	dontcache_io = 1;
 
 int page_size;
 int page_mask;
 int mmap_mask;
-int fsx_rw(int rw, int fd, char *buf, unsigned len, unsigned offset);
+int fsx_rw(int rw, int fd, char *buf, unsigned len, unsigned offset, int flags);
 #define READ 0
 #define WRITE 1
-#define fsxread(a,b,c,d)	fsx_rw(READ, a,b,c,d)
-#define fsxwrite(a,b,c,d)	fsx_rw(WRITE, a,b,c,d)
+#define fsxread(a,b,c,d,f)	fsx_rw(READ, a,b,c,d,f)
+#define fsxwrite(a,b,c,d,f)	fsx_rw(WRITE, a,b,c,d,f)
 
 struct timespec deadline;
 
@@ -266,7 +273,9 @@ prterr(const char *prefix)
 
 static const char *op_names[] = {
 	[OP_READ] = "read",
+	[OP_READ_DONTCACHE] = "read_dontcache",
 	[OP_WRITE] = "write",
+	[OP_WRITE_DONTCACHE] = "write_dontcache",
 	[OP_MAPREAD] = "mapread",
 	[OP_MAPWRITE] = "mapwrite",
 	[OP_TRUNCATE] = "truncate",
@@ -393,12 +402,14 @@ logdump(void)
 				prt("\t******WWWW");
 			break;
 		case OP_READ:
+		case OP_READ_DONTCACHE:
 			prt("READ     0x%x thru 0x%x\t(0x%x bytes)",
 			    lp->args[0], lp->args[0] + lp->args[1] - 1,
 			    lp->args[1]);
 			if (overlap)
 				prt("\t***RRRR***");
 			break;
+		case OP_WRITE_DONTCACHE:
 		case OP_WRITE:
 			prt("WRITE    0x%x thru 0x%x\t(0x%x bytes)",
 			    lp->args[0], lp->args[0] + lp->args[1] - 1,
@@ -784,9 +795,8 @@ doflush(unsigned offset, unsigned size)
 }
 
 void
-doread(unsigned offset, unsigned size)
+doread(unsigned offset, unsigned size, int flags)
 {
-	off_t ret;
 	unsigned iret;
 
 	offset -= offset % readbdy;
@@ -818,12 +828,7 @@ doread(unsigned offset, unsigned size)
 			(monitorend == -1 || offset <= monitorend))))))
 		prt("%lld read\t0x%x thru\t0x%x\t(0x%x bytes)\n", testcalls,
 		    offset, offset + size - 1, size);
-	ret = lseek(fd, (off_t)offset, SEEK_SET);
-	if (ret == (off_t)-1) {
-		prterr("doread: lseek");
-		report_failure(140);
-	}
-	iret = fsxread(fd, temp_buf, size, offset);
+	iret = fsxread(fd, temp_buf, size, offset, flags);
 	if (iret != size) {
 		if (iret == -1)
 			prterr("doread: read");
@@ -870,7 +875,6 @@ check_contents(void)
 	unsigned map_offset;
 	unsigned map_size;
 	char *p;
-	off_t ret;
 	unsigned iret;
 
 	if (!check_buf) {
@@ -885,13 +889,7 @@ check_contents(void)
 	if (size == 0)
 		return;
 
-	ret = lseek(fd, (off_t)offset, SEEK_SET);
-	if (ret == (off_t)-1) {
-		prterr("doread: lseek");
-		report_failure(140);
-	}
-
-	iret = fsxread(fd, check_buf, size, offset);
+	iret = fsxread(fd, check_buf, size, offset, 0);
 	if (iret != size) {
 		if (iret == -1)
 			prterr("check_contents: read");
@@ -1064,9 +1062,8 @@ update_file_size(unsigned offset, unsigned size)
 }
 
 void
-dowrite(unsigned offset, unsigned size)
+dowrite(unsigned offset, unsigned size, int flags)
 {
-	off_t ret;
 	unsigned iret;
 
 	offset -= offset % writebdy;
@@ -1099,14 +1096,9 @@ dowrite(unsigned offset, unsigned size)
 		       (monitorstart == -1 ||
 			(offset + size > monitorstart &&
 			(monitorend == -1 || offset <= monitorend))))))
-		prt("%lld write\t0x%x thru\t0x%x\t(0x%x bytes)\n", testcalls,
-		    offset, offset + size - 1, size);
-	ret = lseek(fd, (off_t)offset, SEEK_SET);
-	if (ret == (off_t)-1) {
-		prterr("dowrite: lseek");
-		report_failure(150);
-	}
-	iret = fsxwrite(fd, good_buf + offset, size, offset);
+		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);
+	iret = fsxwrite(fd, good_buf + offset, size, offset, flags);
 	if (iret != size) {
 		if (iret == -1)
 			prterr("dowrite: write");
@@ -1954,6 +1946,26 @@ do_preallocate(unsigned offset, unsigned length, int keep_size, int unshare)
 }
 #endif
 
+int
+test_dontcache_io(void)
+{
+	char buf[4096];
+	struct iovec iov = { .iov_base = buf, .iov_len = sizeof(buf) };
+	int ret, e;
+
+	ret = preadv2(fd, &iov, 1, 0, RWF_DONTCACHE);
+	e = ret < 0 ? errno : 0;
+	if (e == EOPNOTSUPP) {
+		if (!quiet)
+			fprintf(stderr,
+				"main: filesystem does not support "
+				"dontcache IO, disabling!\n");
+		return 0;
+	}
+
+	return 1;
+}
+
 void
 writefileimage()
 {
@@ -2337,12 +2349,28 @@ have_op:
 	switch (op) {
 	case OP_READ:
 		TRIM_OFF_LEN(offset, size, file_size);
-		doread(offset, size);
+		doread(offset, size, 0);
+		break;
+
+	case OP_READ_DONTCACHE:
+		TRIM_OFF_LEN(offset, size, file_size);
+		if (dontcache_io)
+			doread(offset, size, RWF_DONTCACHE);
+		else
+			doread(offset, size, 0);
 		break;
 
 	case OP_WRITE:
 		TRIM_OFF_LEN(offset, size, maxfilelen);
-		dowrite(offset, size);
+		dowrite(offset, size, 0);
+		break;
+
+	case OP_WRITE_DONTCACHE:
+		TRIM_OFF_LEN(offset, size, maxfilelen);
+		if (dontcache_io)
+			dowrite(offset, size, RWF_DONTCACHE);
+		else
+			dowrite(offset, size, 0);
 		break;
 
 	case OP_MAPREAD:
@@ -2538,6 +2566,7 @@ usage(void)
 "	-0: Do not use exchange range calls\n"
 #endif
 "	-K: Do not use keep size\n\
+	-T: Do not use dontcache IO\n\
 	-L: fsxLite - no file creations & no file size changes\n\
 	-N numops: total # operations to do (default infinity)\n\
 	-O: use oplen (see -o flag) for every op (default random)\n\
@@ -2546,7 +2575,7 @@ usage(void)
 	-S seed: for random # generator (default 1) 0 gets timestamp\n\
 	-W: mapped write operations DISabled\n\
 	-X: Read file and compare to good buffer after every operation\n\
-	-Z: O_DIRECT (use -R, -W, -r and -w too)\n\
+	-Z: O_DIRECT (use -R, -W, -r and -w too, excludes dontcache IO)\n\
 	--replay-ops=opsfile: replay ops from recorded .fsxops file\n\
 	--record-ops[=opsfile]: dump ops file also on success. optionally specify ops file name\n\
 	--duration=seconds: ignore any -N setting and run for this many seconds\n\
@@ -2702,7 +2731,7 @@ uring_setup()
 }
 
 int
-uring_rw(int rw, int fd, char *buf, unsigned len, unsigned offset)
+uring_rw(int rw, int fd, char *buf, unsigned len, unsigned offset, int flags)
 {
 	struct io_uring_sqe     *sqe;
 	struct io_uring_cqe     *cqe;
@@ -2733,6 +2762,7 @@ uring_rw(int rw, int fd, char *buf, unsigned len, unsigned offset)
 		} else {
 			io_uring_prep_writev(sqe, fd, &iovec, 1, o);
 		}
+		sqe->rw_flags = flags;
 
 		ret = io_uring_submit_and_wait(&ring, 1);
 		if (ret != 1) {
@@ -2781,7 +2811,7 @@ uring_rw(int rw, int fd, char *buf, unsigned len, unsigned offset)
 }
 #else
 int
-uring_rw(int rw, int fd, char *buf, unsigned len, unsigned offset)
+uring_rw(int rw, int fd, char *buf, unsigned len, unsigned offset, int flags)
 {
 	fprintf(stderr, "io_rw: need IO_URING support!\n");
 	exit(111);
@@ -2789,19 +2819,21 @@ uring_rw(int rw, int fd, char *buf, unsigned len, unsigned offset)
 #endif
 
 int
-fsx_rw(int rw, int fd, char *buf, unsigned len, unsigned offset)
+fsx_rw(int rw, int fd, char *buf, unsigned len, unsigned offset, int flags)
 {
 	int ret;
 
 	if (aio) {
 		ret = aio_rw(rw, fd, buf, len, offset);
 	} else if (uring) {
-		ret = uring_rw(rw, fd, buf, len, offset);
+		ret = uring_rw(rw, fd, buf, len, offset, flags);
 	} else {
+		struct iovec iov = { .iov_base = buf, .iov_len = len };
+
 		if (rw == READ)
-			ret = read(fd, buf, len);
+			ret = preadv2(fd, &iov, 1, offset, flags);
 		else
-			ret = write(fd, buf, len);
+			ret = pwritev2(fd, &iov, 1, offset, flags);
 	}
 	return ret;
 }
@@ -3065,6 +3097,9 @@ main(int argc, char **argv)
 			if (seed < 0)
 				usage();
 			break;
+		case 'T':
+			dontcache_io = 0;
+			break;
 		case 'W':
 		        mapped_writes = 0;
 			if (!quiet)
@@ -3076,6 +3111,7 @@ main(int argc, char **argv)
 		case 'Z':
 			o_direct = O_DIRECT;
 			o_flags |= O_DIRECT;
+			dontcache_io = 0;
 			break;
 		case 254:  /* --duration */
 			if (!optarg) {
@@ -3293,6 +3329,9 @@ main(int argc, char **argv)
 		copy_range_calls = test_copy_range();
 	if (exchange_range_calls)
 		exchange_range_calls = test_exchange_range();
+	if (dontcache_io)
+		dontcache_io = test_dontcache_io();
+	printf("Dontcache_io=%d\n", dontcache_io);
 
 	while (keep_running())
 		if (!test())
-- 
2.47.1

Re: [PATCH 2/2] fsx: add support for RWF_DONTCACHE

[Darrick J. Wong]

On Mon, Jan 06, 2025 at 10:48:47AM -0700, Jens Axboe wrote:
> Using RWF_DONTCACHE tells the kernel that any page cache instantiated
> by this operation should get pruned once the operation completes. If
> data is in cache prior to the operation it will remain there.
> 
> Add ops for testing both the read and write side of this. At startup,
> kernel support for this feature is probed. If support isn't available,
> uncached/dontcache IO is performed as regular buffered IO. If -Z is
> used to turn on O_DIRECT, then uncached/dontcache IO isn't performed.
> Defaults to on if available, and adds a -T parameter to turn it off.
> 
> See the kernel posting adding support:
> 
> https://lore.kernel.org/linux-fsdevel/20241220154831.1086649-1-axboe@kernel.dk/
> 
> Signed-off-by: Jens Axboe <axboe@kernel.dk>
> ---
>  ltp/fsx.c | 115 ++++++++++++++++++++++++++++++++++++------------------
>  1 file changed, 77 insertions(+), 38 deletions(-)
> 
> diff --git a/ltp/fsx.c b/ltp/fsx.c
> index 41933354328a..7c996026157d 100644
> --- a/ltp/fsx.c
> +++ b/ltp/fsx.c
> @@ -43,6 +43,10 @@
>  # define MAP_FILE 0
>  #endif
>  
> +#ifndef RWF_DONTCACHE
> +#define RWF_DONTCACHE	0x80
> +#endif
> +
>  #define NUMPRINTCOLUMNS 32	/* # columns of data to print on each line */
>  
>  /* Operation flags (bitmask) */
> @@ -101,7 +105,9 @@ int			logcount = 0;	/* total ops */
>  enum {
>  	/* common operations */
>  	OP_READ = 0,
> +	OP_READ_DONTCACHE,
>  	OP_WRITE,
> +	OP_WRITE_DONTCACHE,
>  	OP_MAPREAD,
>  	OP_MAPWRITE,
>  	OP_MAX_LITE,
> @@ -190,15 +196,16 @@ int	o_direct;			/* -Z */
>  int	aio = 0;
>  int	uring = 0;
>  int	mark_nr = 0;
> +int	dontcache_io = 1;
>  
>  int page_size;
>  int page_mask;
>  int mmap_mask;
> -int fsx_rw(int rw, int fd, char *buf, unsigned len, unsigned offset);
> +int fsx_rw(int rw, int fd, char *buf, unsigned len, unsigned offset, int flags);
>  #define READ 0
>  #define WRITE 1
> -#define fsxread(a,b,c,d)	fsx_rw(READ, a,b,c,d)
> -#define fsxwrite(a,b,c,d)	fsx_rw(WRITE, a,b,c,d)
> +#define fsxread(a,b,c,d,f)	fsx_rw(READ, a,b,c,d,f)
> +#define fsxwrite(a,b,c,d,f)	fsx_rw(WRITE, a,b,c,d,f)
>  
>  struct timespec deadline;
>  
> @@ -266,7 +273,9 @@ prterr(const char *prefix)
>  
>  static const char *op_names[] = {
>  	[OP_READ] = "read",
> +	[OP_READ_DONTCACHE] = "read_dontcache",
>  	[OP_WRITE] = "write",
> +	[OP_WRITE_DONTCACHE] = "write_dontcache",
>  	[OP_MAPREAD] = "mapread",
>  	[OP_MAPWRITE] = "mapwrite",
>  	[OP_TRUNCATE] = "truncate",
> @@ -393,12 +402,14 @@ logdump(void)
>  				prt("\t******WWWW");
>  			break;
>  		case OP_READ:
> +		case OP_READ_DONTCACHE:
>  			prt("READ     0x%x thru 0x%x\t(0x%x bytes)",
>  			    lp->args[0], lp->args[0] + lp->args[1] - 1,
>  			    lp->args[1]);
>  			if (overlap)
>  				prt("\t***RRRR***");
>  			break;
> +		case OP_WRITE_DONTCACHE:
>  		case OP_WRITE:
>  			prt("WRITE    0x%x thru 0x%x\t(0x%x bytes)",
>  			    lp->args[0], lp->args[0] + lp->args[1] - 1,
> @@ -784,9 +795,8 @@ doflush(unsigned offset, unsigned size)
>  }
>  
>  void
> -doread(unsigned offset, unsigned size)
> +doread(unsigned offset, unsigned size, int flags)
>  {
> -	off_t ret;
>  	unsigned iret;
>  
>  	offset -= offset % readbdy;
> @@ -818,12 +828,7 @@ doread(unsigned offset, unsigned size)
>  			(monitorend == -1 || offset <= monitorend))))))
>  		prt("%lld read\t0x%x thru\t0x%x\t(0x%x bytes)\n", testcalls,
>  		    offset, offset + size - 1, size);
> -	ret = lseek(fd, (off_t)offset, SEEK_SET);
> -	if (ret == (off_t)-1) {
> -		prterr("doread: lseek");
> -		report_failure(140);
> -	}
> -	iret = fsxread(fd, temp_buf, size, offset);
> +	iret = fsxread(fd, temp_buf, size, offset, flags);
>  	if (iret != size) {
>  		if (iret == -1)
>  			prterr("doread: read");
> @@ -870,7 +875,6 @@ check_contents(void)
>  	unsigned map_offset;
>  	unsigned map_size;
>  	char *p;
> -	off_t ret;
>  	unsigned iret;
>  
>  	if (!check_buf) {
> @@ -885,13 +889,7 @@ check_contents(void)
>  	if (size == 0)
>  		return;
>  
> -	ret = lseek(fd, (off_t)offset, SEEK_SET);
> -	if (ret == (off_t)-1) {
> -		prterr("doread: lseek");
> -		report_failure(140);
> -	}
> -
> -	iret = fsxread(fd, check_buf, size, offset);
> +	iret = fsxread(fd, check_buf, size, offset, 0);
>  	if (iret != size) {
>  		if (iret == -1)
>  			prterr("check_contents: read");
> @@ -1064,9 +1062,8 @@ update_file_size(unsigned offset, unsigned size)
>  }
>  
>  void
> -dowrite(unsigned offset, unsigned size)
> +dowrite(unsigned offset, unsigned size, int flags)
>  {
> -	off_t ret;
>  	unsigned iret;
>  
>  	offset -= offset % writebdy;
> @@ -1099,14 +1096,9 @@ dowrite(unsigned offset, unsigned size)
>  		       (monitorstart == -1 ||
>  			(offset + size > monitorstart &&
>  			(monitorend == -1 || offset <= monitorend))))))
> -		prt("%lld write\t0x%x thru\t0x%x\t(0x%x bytes)\n", testcalls,
> -		    offset, offset + size - 1, size);
> -	ret = lseek(fd, (off_t)offset, SEEK_SET);
> -	if (ret == (off_t)-1) {
> -		prterr("dowrite: lseek");
> -		report_failure(150);
> -	}
> -	iret = fsxwrite(fd, good_buf + offset, size, offset);
> +		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);
> +	iret = fsxwrite(fd, good_buf + offset, size, offset, flags);
>  	if (iret != size) {
>  		if (iret == -1)
>  			prterr("dowrite: write");
> @@ -1954,6 +1946,26 @@ do_preallocate(unsigned offset, unsigned length, int keep_size, int unshare)
>  }
>  #endif
>  
> +int
> +test_dontcache_io(void)
> +{
> +	char buf[4096];
> +	struct iovec iov = { .iov_base = buf, .iov_len = sizeof(buf) };
> +	int ret, e;
> +
> +	ret = preadv2(fd, &iov, 1, 0, RWF_DONTCACHE);
> +	e = ret < 0 ? errno : 0;
> +	if (e == EOPNOTSUPP) {
> +		if (!quiet)
> +			fprintf(stderr,
> +				"main: filesystem does not support "
> +				"dontcache IO, disabling!\n");
> +		return 0;
> +	}
> +
> +	return 1;
> +}
> +
>  void
>  writefileimage()
>  {
> @@ -2337,12 +2349,28 @@ have_op:
>  	switch (op) {
>  	case OP_READ:
>  		TRIM_OFF_LEN(offset, size, file_size);
> -		doread(offset, size);
> +		doread(offset, size, 0);
> +		break;
> +
> +	case OP_READ_DONTCACHE:
> +		TRIM_OFF_LEN(offset, size, file_size);
> +		if (dontcache_io)
> +			doread(offset, size, RWF_DONTCACHE);
> +		else
> +			doread(offset, size, 0);
>  		break;
>  
>  	case OP_WRITE:
>  		TRIM_OFF_LEN(offset, size, maxfilelen);
> -		dowrite(offset, size);
> +		dowrite(offset, size, 0);
> +		break;
> +
> +	case OP_WRITE_DONTCACHE:
> +		TRIM_OFF_LEN(offset, size, maxfilelen);
> +		if (dontcache_io)
> +			dowrite(offset, size, RWF_DONTCACHE);
> +		else
> +			dowrite(offset, size, 0);
>  		break;
>  
>  	case OP_MAPREAD:
> @@ -2538,6 +2566,7 @@ usage(void)
>  "	-0: Do not use exchange range calls\n"
>  #endif
>  "	-K: Do not use keep size\n\
> +	-T: Do not use dontcache IO\n\
>  	-L: fsxLite - no file creations & no file size changes\n\
>  	-N numops: total # operations to do (default infinity)\n\
>  	-O: use oplen (see -o flag) for every op (default random)\n\
> @@ -2546,7 +2575,7 @@ usage(void)
>  	-S seed: for random # generator (default 1) 0 gets timestamp\n\
>  	-W: mapped write operations DISabled\n\
>  	-X: Read file and compare to good buffer after every operation\n\
> -	-Z: O_DIRECT (use -R, -W, -r and -w too)\n\
> +	-Z: O_DIRECT (use -R, -W, -r and -w too, excludes dontcache IO)\n\
>  	--replay-ops=opsfile: replay ops from recorded .fsxops file\n\
>  	--record-ops[=opsfile]: dump ops file also on success. optionally specify ops file name\n\
>  	--duration=seconds: ignore any -N setting and run for this many seconds\n\
> @@ -2702,7 +2731,7 @@ uring_setup()
>  }
>  
>  int
> -uring_rw(int rw, int fd, char *buf, unsigned len, unsigned offset)
> +uring_rw(int rw, int fd, char *buf, unsigned len, unsigned offset, int flags)
>  {
>  	struct io_uring_sqe     *sqe;
>  	struct io_uring_cqe     *cqe;
> @@ -2733,6 +2762,7 @@ uring_rw(int rw, int fd, char *buf, unsigned len, unsigned offset)
>  		} else {
>  			io_uring_prep_writev(sqe, fd, &iovec, 1, o);
>  		}
> +		sqe->rw_flags = flags;
>  
>  		ret = io_uring_submit_and_wait(&ring, 1);
>  		if (ret != 1) {
> @@ -2781,7 +2811,7 @@ uring_rw(int rw, int fd, char *buf, unsigned len, unsigned offset)
>  }
>  #else
>  int
> -uring_rw(int rw, int fd, char *buf, unsigned len, unsigned offset)
> +uring_rw(int rw, int fd, char *buf, unsigned len, unsigned offset, int flags)
>  {
>  	fprintf(stderr, "io_rw: need IO_URING support!\n");
>  	exit(111);
> @@ -2789,19 +2819,21 @@ uring_rw(int rw, int fd, char *buf, unsigned len, unsigned offset)
>  #endif
>  
>  int
> -fsx_rw(int rw, int fd, char *buf, unsigned len, unsigned offset)
> +fsx_rw(int rw, int fd, char *buf, unsigned len, unsigned offset, int flags)
>  {
>  	int ret;
>  
>  	if (aio) {
>  		ret = aio_rw(rw, fd, buf, len, offset);
>  	} else if (uring) {
> -		ret = uring_rw(rw, fd, buf, len, offset);
> +		ret = uring_rw(rw, fd, buf, len, offset, flags);
>  	} else {
> +		struct iovec iov = { .iov_base = buf, .iov_len = len };
> +
>  		if (rw == READ)
> -			ret = read(fd, buf, len);
> +			ret = preadv2(fd, &iov, 1, offset, flags);
>  		else
> -			ret = write(fd, buf, len);
> +			ret = pwritev2(fd, &iov, 1, offset, flags);
>  	}
>  	return ret;
>  }
> @@ -3065,6 +3097,9 @@ main(int argc, char **argv)
>  			if (seed < 0)
>  				usage();
>  			break;
> +		case 'T':
> +			dontcache_io = 0;
> +			break;
>  		case 'W':
>  		        mapped_writes = 0;
>  			if (!quiet)
> @@ -3076,6 +3111,7 @@ main(int argc, char **argv)
>  		case 'Z':
>  			o_direct = O_DIRECT;
>  			o_flags |= O_DIRECT;
> +			dontcache_io = 0;
>  			break;
>  		case 254:  /* --duration */
>  			if (!optarg) {
> @@ -3293,6 +3329,9 @@ main(int argc, char **argv)
>  		copy_range_calls = test_copy_range();
>  	if (exchange_range_calls)
>  		exchange_range_calls = test_exchange_range();
> +	if (dontcache_io)
> +		dontcache_io = test_dontcache_io();
> +	printf("Dontcache_io=%d\n", dontcache_io);

Is this a debug printf that got left in by mistake?

(Everything else in here looks fine to me...)

--D

>  
>  	while (keep_running())
>  		if (!test())
> -- 
> 2.47.1
> 
> 

Re: [PATCH 1/2] fsstress: add support for RWF_DONTCACHE

[Darrick J. Wong]

On Mon, Jan 06, 2025 at 10:48:46AM -0700, Jens Axboe wrote:
> Using RWF_DONTCACHE tells the kernel that any page cache instantiated
> by this operation should get pruned once the operation completes. If
> data is in cache prior to the operation it will remain there.
> 
> Add ops for testing both the read and write side of this. If the kernel
> being tested doesn't support RWF_DONTCACHE, then operations are performed
> with regular read/write buffered IO.
> 
> See the kernel posting adding support:
> 
> https://lore.kernel.org/linux-fsdevel/20241220154831.1086649-1-axboe@kernel.dk/
> 
> Signed-off-by: Jens Axboe <axboe@kernel.dk>
> ---
>  ltp/fsstress.c | 136 +++++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 136 insertions(+)
> 
> diff --git a/ltp/fsstress.c b/ltp/fsstress.c
> index 3d248ee25791..df9f6ffb86fc 100644
> --- a/ltp/fsstress.c
> +++ b/ltp/fsstress.c
> @@ -82,6 +82,12 @@ static int renameat2(int dfd1, const char *path1,
>  #define RENAME_WHITEOUT		(1 << 2)	/* Whiteout source */
>  #endif
>  
> +#ifndef RWF_DONTCACHE
> +#define RWF_DONTCACHE		0x80
> +#endif
> +
> +static int have_rwf_dontcache = 1;
> +
>  #define FILELEN_MAX		(32*4096)
>  
>  typedef enum {
> @@ -117,6 +123,7 @@ typedef enum {
>  	OP_COLLAPSE,
>  	OP_INSERT,
>  	OP_READ,
> +	OP_READ_DONTCACHE,
>  	OP_READLINK,
>  	OP_READV,
>  	OP_REMOVEFATTR,
> @@ -143,6 +150,7 @@ typedef enum {
>  	OP_URING_READ,
>  	OP_URING_WRITE,
>  	OP_WRITE,
> +	OP_WRITE_DONTCACHE,
>  	OP_WRITEV,
>  	OP_EXCHANGE_RANGE,
>  	OP_LAST
> @@ -248,6 +256,7 @@ void	zero_f(opnum_t, long);
>  void	collapse_f(opnum_t, long);
>  void	insert_f(opnum_t, long);
>  void	unshare_f(opnum_t, long);
> +void	read_dontcache_f(opnum_t, long);
>  void	read_f(opnum_t, long);
>  void	readlink_f(opnum_t, long);
>  void	readv_f(opnum_t, long);
> @@ -273,6 +282,7 @@ void	unlink_f(opnum_t, long);
>  void	unresvsp_f(opnum_t, long);
>  void	uring_read_f(opnum_t, long);
>  void	uring_write_f(opnum_t, long);
> +void	write_dontcache_f(opnum_t, long);
>  void	write_f(opnum_t, long);
>  void	writev_f(opnum_t, long);
>  void	exchangerange_f(opnum_t, long);
> @@ -315,6 +325,7 @@ struct opdesc	ops[OP_LAST]	= {
>  	[OP_COLLAPSE]	   = {"collapse",      collapse_f,	1, 1 },
>  	[OP_INSERT]	   = {"insert",	       insert_f,	1, 1 },
>  	[OP_READ]	   = {"read",	       read_f,		1, 0 },
> +	[OP_READ_DONTCACHE] = {"read_dontcache", read_dontcache_f,	1, 0 },
>  	[OP_READLINK]	   = {"readlink",      readlink_f,	1, 0 },
>  	[OP_READV]	   = {"readv",	       readv_f,		1, 0 },
>  	/* remove (delete) extended attribute */
> @@ -346,6 +357,7 @@ struct opdesc	ops[OP_LAST]	= {
>  	[OP_URING_WRITE]   = {"uring_write",   uring_write_f,	1, 1 },
>  	[OP_WRITE]	   = {"write",	       write_f,		4, 1 },
>  	[OP_WRITEV]	   = {"writev",	       writev_f,	4, 1 },
> +	[OP_WRITE_DONTCACHE]= {"write_dontcache", write_dontcache_f,4, 1 },
>  	[OP_EXCHANGE_RANGE]= {"exchangerange", exchangerange_f,	2, 1 },
>  }, *ops_end;
>  
> @@ -4635,6 +4647,71 @@ readv_f(opnum_t opno, long r)
>  	close(fd);
>  }
>  
> +void
> +read_dontcache_f(opnum_t opno, long r)
> +{
> +	int		e;
> +	pathname_t	f;
> +	int		fd;
> +	int64_t		lr;
> +	off64_t		off;
> +	struct stat64	stb;
> +	int		v;
> +	char		st[1024];
> +	struct iovec	iov;
> +	int flags;
> +
> +	init_pathname(&f);
> +	if (!get_fname(FT_REGFILE, r, &f, NULL, NULL, &v)) {
> +		if (v)
> +			printf("%d/%lld: read - no filename\n", procid, opno);
> +		free_pathname(&f);
> +		return;
> +	}
> +	fd = open_path(&f, O_RDONLY);
> +	e = fd < 0 ? errno : 0;
> +	check_cwd();
> +	if (fd < 0) {
> +		if (v)
> +			printf("%d/%lld: read - open %s failed %d\n",
> +				procid, opno, f.path, e);
> +		free_pathname(&f);
> +		return;
> +	}
> +	if (fstat64(fd, &stb) < 0) {
> +		if (v)
> +			printf("%d/%lld: read - fstat64 %s failed %d\n",
> +				procid, opno, f.path, errno);
> +		free_pathname(&f);
> +		close(fd);
> +		return;
> +	}
> +	inode_info(st, sizeof(st), &stb, v);
> +	if (stb.st_size == 0) {
> +		if (v)
> +			printf("%d/%lld: read - %s%s zero size\n", procid, opno,
> +			       f.path, st);
> +		free_pathname(&f);
> +		close(fd);
> +		return;
> +	}
> +	lr = ((int64_t)random() << 32) + random();
> +	off = (off64_t)(lr % stb.st_size);
> +	iov.iov_len = (random() % FILELEN_MAX) + 1;
> +	iov.iov_base = malloc(iov.iov_len);

Should there be a check for null iov_base after the allocation?

> +	flags = have_rwf_dontcache ? RWF_DONTCACHE : 0;
> +	e = preadv2(fd, &iov, 1, off, flags) < 0 ? errno : 0;
> +	if (have_rwf_dontcache && e == EOPNOTSUPP)

...and should this set have_rwf_dontcache = 0?

(Other than that, thanks for wiring this up...)

--D

> +		e = preadv2(fd, &iov, 1, off, 0) < 0 ? errno : 0;
> +	free(iov.iov_base);
> +	if (v)
> +		printf("%d/%lld: read dontcache %s%s [%lld,%d] %d\n",
> +		       procid, opno, f.path, st, (long long)off,
> +		       (int)iov.iov_len, e);
> +	free_pathname(&f);
> +	close(fd);
> +}
> +
>  void
>  removefattr_f(opnum_t opno, long r)
>  {
> @@ -5509,6 +5586,65 @@ writev_f(opnum_t opno, long r)
>  	close(fd);
>  }
>  
> +void
> +write_dontcache_f(opnum_t opno, long r)
> +{
> +	int		e;
> +	pathname_t	f;
> +	int		fd;
> +	int64_t		lr;
> +	off64_t		off;
> +	struct stat64	stb;
> +	int		v;
> +	char		st[1024];
> +	struct iovec	iov;
> +	int flags;
> +
> +	init_pathname(&f);
> +	if (!get_fname(FT_REGm, r, &f, NULL, NULL, &v)) {
> +		if (v)
> +			printf("%d/%lld: write - no filename\n", procid, opno);
> +		free_pathname(&f);
> +		return;
> +	}
> +	fd = open_path(&f, O_WRONLY);
> +	e = fd < 0 ? errno : 0;
> +	check_cwd();
> +	if (fd < 0) {
> +		if (v)
> +			printf("%d/%lld: write - open %s failed %d\n",
> +				procid, opno, f.path, e);
> +		free_pathname(&f);
> +		return;
> +	}
> +	if (fstat64(fd, &stb) < 0) {
> +		if (v)
> +			printf("%d/%lld: write - fstat64 %s failed %d\n",
> +				procid, opno, f.path, errno);
> +		free_pathname(&f);
> +		close(fd);
> +		return;
> +	}
> +	inode_info(st, sizeof(st), &stb, v);
> +	lr = ((int64_t)random() << 32) + random();
> +	off = (off64_t)(lr % MIN(stb.st_size + (1024 * 1024), MAXFSIZE));
> +	off %= maxfsize;
> +	iov.iov_len = (random() % FILELEN_MAX) + 1;
> +	iov.iov_base = malloc(iov.iov_len);
> +	memset(iov.iov_base, nameseq & 0xff, iov.iov_len);
> +	flags = have_rwf_dontcache ? RWF_DONTCACHE : 0;
> +	e = pwritev2(fd, &iov, 1, off, flags) < 0 ? errno : 0;
> +	if (have_rwf_dontcache && e == EOPNOTSUPP)
> +		e = pwritev2(fd, &iov, 1, off, 0) < 0 ? errno : 0;
> +	free(iov.iov_base);
> +	if (v)
> +		printf("%d/%lld: write dontcache %s%s [%lld,%d] %d\n",
> +		       procid, opno, f.path, st, (long long)off,
> +		       (int)iov.iov_len, e);
> +	free_pathname(&f);
> +	close(fd);
> +}
> +
>  char *
>  xattr_flag_to_string(int flag)
>  {
> -- 
> 2.47.1
> 
> 

Re: [PATCH 2/2] fsx: add support for RWF_DONTCACHE

[Jens Axboe]

On 1/6/25 7:09 PM, Darrick J. Wong wrote:
>> @@ -3293,6 +3329,9 @@ main(int argc, char **argv)
>>  		copy_range_calls = test_copy_range();
>>  	if (exchange_range_calls)
>>  		exchange_range_calls = test_exchange_range();
>> +	if (dontcache_io)
>> +		dontcache_io = test_dontcache_io();
>> +	printf("Dontcache_io=%d\n", dontcache_io);
> 
> Is this a debug printf that got left in by mistake?
> 
> (Everything else in here looks fine to me...)

Oops indeed yes, good catch!

-- 
Jens Axboe

Re: [PATCH 1/2] fsstress: add support for RWF_DONTCACHE

[Jens Axboe]

On 1/6/25 7:11 PM, Darrick J. Wong wrote:
>> +void
>> +read_dontcache_f(opnum_t opno, long r)
>> +{
>> +	int		e;
>> +	pathname_t	f;
>> +	int		fd;
>> +	int64_t		lr;
>> +	off64_t		off;
>> +	struct stat64	stb;
>> +	int		v;
>> +	char		st[1024];
>> +	struct iovec	iov;
>> +	int flags;
>> +
>> +	init_pathname(&f);
>> +	if (!get_fname(FT_REGFILE, r, &f, NULL, NULL, &v)) {
>> +		if (v)
>> +			printf("%d/%lld: read - no filename\n", procid, opno);
>> +		free_pathname(&f);
>> +		return;
>> +	}
>> +	fd = open_path(&f, O_RDONLY);
>> +	e = fd < 0 ? errno : 0;
>> +	check_cwd();
>> +	if (fd < 0) {
>> +		if (v)
>> +			printf("%d/%lld: read - open %s failed %d\n",
>> +				procid, opno, f.path, e);
>> +		free_pathname(&f);
>> +		return;
>> +	}
>> +	if (fstat64(fd, &stb) < 0) {
>> +		if (v)
>> +			printf("%d/%lld: read - fstat64 %s failed %d\n",
>> +				procid, opno, f.path, errno);
>> +		free_pathname(&f);
>> +		close(fd);
>> +		return;
>> +	}
>> +	inode_info(st, sizeof(st), &stb, v);
>> +	if (stb.st_size == 0) {
>> +		if (v)
>> +			printf("%d/%lld: read - %s%s zero size\n", procid, opno,
>> +			       f.path, st);
>> +		free_pathname(&f);
>> +		close(fd);
>> +		return;
>> +	}
>> +	lr = ((int64_t)random() << 32) + random();
>> +	off = (off64_t)(lr % stb.st_size);
>> +	iov.iov_len = (random() % FILELEN_MAX) + 1;
>> +	iov.iov_base = malloc(iov.iov_len);
> 
> Should there be a check for null iov_base after the allocation?

Nothing else in fsstress seems to bother with malloc() failures, which
at least on Linux, is probably fair game.

>> +	flags = have_rwf_dontcache ? RWF_DONTCACHE : 0;
>> +	e = preadv2(fd, &iov, 1, off, flags) < 0 ? errno : 0;
>> +	if (have_rwf_dontcache && e == EOPNOTSUPP)
> 
> ...and should this set have_rwf_dontcache = 0?

I don't think so? If we get EOPNOTSUPP and we don't have dontcache, then
it's a fatal condition. fsstress defaults to it being available, so we
may very well run into EOPNOTSUPP and then just do a regular read or
write for that case. We could probably do:

if (have_rwf_dontcache && e == EOPNOTSUPP) {
	have_rwf_dontcache = 0;
	e = preadv2(fd, &iov, 1, off, 0) < 0 ? errno : 0;
}

here and on the write side, at least then we won't repeatedly try
RWF_DONTCACHE if we hit EOPNOTSUPP. But in terms of logic, it should be
correct as-is.

-- 
Jens Axboe

Re: [PATCH 1/2] fsstress: add support for RWF_DONTCACHE

[Darrick J. Wong]

On Mon, Jan 06, 2025 at 07:16:17PM -0700, Jens Axboe wrote:
> On 1/6/25 7:11 PM, Darrick J. Wong wrote:
> >> +void
> >> +read_dontcache_f(opnum_t opno, long r)
> >> +{
> >> +	int		e;
> >> +	pathname_t	f;
> >> +	int		fd;
> >> +	int64_t		lr;
> >> +	off64_t		off;
> >> +	struct stat64	stb;
> >> +	int		v;
> >> +	char		st[1024];
> >> +	struct iovec	iov;
> >> +	int flags;
> >> +
> >> +	init_pathname(&f);
> >> +	if (!get_fname(FT_REGFILE, r, &f, NULL, NULL, &v)) {
> >> +		if (v)
> >> +			printf("%d/%lld: read - no filename\n", procid, opno);
> >> +		free_pathname(&f);
> >> +		return;
> >> +	}
> >> +	fd = open_path(&f, O_RDONLY);
> >> +	e = fd < 0 ? errno : 0;
> >> +	check_cwd();
> >> +	if (fd < 0) {
> >> +		if (v)
> >> +			printf("%d/%lld: read - open %s failed %d\n",
> >> +				procid, opno, f.path, e);
> >> +		free_pathname(&f);
> >> +		return;
> >> +	}
> >> +	if (fstat64(fd, &stb) < 0) {
> >> +		if (v)
> >> +			printf("%d/%lld: read - fstat64 %s failed %d\n",
> >> +				procid, opno, f.path, errno);
> >> +		free_pathname(&f);
> >> +		close(fd);
> >> +		return;
> >> +	}
> >> +	inode_info(st, sizeof(st), &stb, v);
> >> +	if (stb.st_size == 0) {
> >> +		if (v)
> >> +			printf("%d/%lld: read - %s%s zero size\n", procid, opno,
> >> +			       f.path, st);
> >> +		free_pathname(&f);
> >> +		close(fd);
> >> +		return;
> >> +	}
> >> +	lr = ((int64_t)random() << 32) + random();
> >> +	off = (off64_t)(lr % stb.st_size);
> >> +	iov.iov_len = (random() % FILELEN_MAX) + 1;
> >> +	iov.iov_base = malloc(iov.iov_len);
> > 
> > Should there be a check for null iov_base after the allocation?
> 
> Nothing else in fsstress seems to bother with malloc() failures, which
> at least on Linux, is probably fair game.

lol ok.

> >> +	flags = have_rwf_dontcache ? RWF_DONTCACHE : 0;
> >> +	e = preadv2(fd, &iov, 1, off, flags) < 0 ? errno : 0;
> >> +	if (have_rwf_dontcache && e == EOPNOTSUPP)
> > 
> > ...and should this set have_rwf_dontcache = 0?
> 
> I don't think so? If we get EOPNOTSUPP and we don't have dontcache, then
> it's a fatal condition. fsstress defaults to it being available, so we
> may very well run into EOPNOTSUPP and then just do a regular read or
> write for that case. We could probably do:
> 
> if (have_rwf_dontcache && e == EOPNOTSUPP) {
> 	have_rwf_dontcache = 0;
> 	e = preadv2(fd, &iov, 1, off, 0) < 0 ? errno : 0;
> }

Yep, that's exactly what I was thinking. :)

--D

> here and on the write side, at least then we won't repeatedly try
> RWF_DONTCACHE if we hit EOPNOTSUPP. But in terms of logic, it should be
> correct as-is.
> 
> -- 
> Jens Axboe
>