[PATCH] mke2fs: Warn if fs block size is incompatible with DAX

* [PATCH] mke2fs: Warn if fs block size is incompatible with DAX
@ 2020-07-09 14:40 Jan Kara
  2020-08-05 14:15 ` Jan Kara
  2020-10-01 14:31 ` Theodore Y. Ts'o
  0 siblings, 2 replies; 3+ messages in thread
From: Jan Kara @ 2020-07-09 14:40 UTC (permalink / raw)
  To: Ted Tso; +Cc: linux-ext4, Jan Kara

If we are creating filesystem on DAX capable device, warn if set block
size is incompatible with DAX to give admin some hint why DAX might not
be available.

Signed-off-by: Jan Kara <jack@suse.cz>
---
 configure.ac  |  3 +++
 misc/mke2fs.c | 81 ++++++++++++++++++++++++++++++++++++++---------------------
 2 files changed, 55 insertions(+), 29 deletions(-)

diff --git a/configure.ac b/configure.ac
index 18e434bc6ebc..7d9210740387 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1142,6 +1142,9 @@ if test -n "$BLKID_CMT"; then
   AC_CHECK_LIB(blkid, blkid_probe_get_topology,
 		      AC_DEFINE(HAVE_BLKID_PROBE_GET_TOPOLOGY, 1,
 				[Define to 1 if blkid has blkid_probe_get_topology]))
+  AC_CHECK_LIB(blkid, blkid_topology_get_dax,
+		      AC_DEFINE(HAVE_BLKID_TOPOLOGY_GET_DAX, 1,
+				[Define to 1 if blkid has blkid_topology_get_dax]))
   AC_CHECK_LIB(blkid, blkid_probe_enable_partitions,
 		      AC_DEFINE(HAVE_BLKID_PROBE_ENABLE_PARTITIONS, 1,
 				[Define to 1 if blkid has blkid_probe_enable_partitions]))
diff --git a/misc/mke2fs.c b/misc/mke2fs.c
index c90dcf0e87c1..8c8f5ea467d3 100644
--- a/misc/mke2fs.c
+++ b/misc/mke2fs.c
@@ -1468,23 +1468,30 @@ int get_bool_from_profile(char **types, const char *opt, int def_val)
 extern const char *mke2fs_default_profile;
 static const char *default_files[] = { "<default>", 0 };
 
+struct device_param {
+	unsigned long min_io;		/* prefered minimum IO size */
+	unsigned long opt_io;		/* optimal IO size */
+	unsigned long alignment_offset;	/* alignment offset wrt physical block size */
+	unsigned int dax:1;		/* supports dax? */
+};
+
 #ifdef HAVE_BLKID_PROBE_GET_TOPOLOGY
 /*
  * Sets the geometry of a device (stripe/stride), and returns the
  * device's alignment offset, if any, or a negative error.
  */
 static int get_device_geometry(const char *file,
-			       struct ext2_super_block *param,
-			       unsigned int psector_size)
+			       unsigned int blocksize,
+			       unsigned int psector_size,
+			       struct device_param *dev_param)
 {
 	int rc = -1;
-	unsigned int blocksize;
 	blkid_probe pr;
 	blkid_topology tp;
-	unsigned long min_io;
-	unsigned long opt_io;
 	struct stat statbuf;
 
+	memset(dev_param, 0, sizeof(*dev_param));
+
 	/* Nothing to do for a regular file */
 	if (!stat(file, &statbuf) && S_ISREG(statbuf.st_mode))
 		return 0;
@@ -1497,23 +1504,20 @@ static int get_device_geometry(const char *file,
 	if (!tp)
 		goto out;
 
-	min_io = blkid_topology_get_minimum_io_size(tp);
-	opt_io = blkid_topology_get_optimal_io_size(tp);
-	blocksize = EXT2_BLOCK_SIZE(param);
-	if ((min_io == 0) && (psector_size > blocksize))
-		min_io = psector_size;
-	if ((opt_io == 0) && min_io)
-		opt_io = min_io;
-	if ((opt_io == 0) && (psector_size > blocksize))
-		opt_io = psector_size;
-
-	/* setting stripe/stride to blocksize is pointless */
-	if (min_io > blocksize)
-		param->s_raid_stride = min_io / blocksize;
-	if (opt_io > blocksize)
-		param->s_raid_stripe_width = opt_io / blocksize;
-
-	rc = blkid_topology_get_alignment_offset(tp);
+	dev_param->min_io = blkid_topology_get_minimum_io_size(tp);
+	dev_param->opt_io = blkid_topology_get_optimal_io_size(tp);
+	if ((dev_param->min_io == 0) && (psector_size > blocksize))
+		dev_param->min_io = psector_size;
+	if ((dev_param->opt_io == 0) && dev_param->min_io > 0)
+		dev_param->opt_io = dev_param->min_io;
+	if ((dev_param->opt_io == 0) && (psector_size > blocksize))
+		dev_param->opt_io = psector_size;
+
+	dev_param->alignment_offset = blkid_topology_get_alignment_offset(tp);
+#ifdef HAVE_BLKID_TOPOLOGY_GET_DAX
+	dev_param->dax = blkid_topology_get_dax(tp);
+#endif
+	rc = 0;
 out:
 	blkid_free_probe(pr);
 	return rc;
@@ -1562,6 +1566,7 @@ static void PRS(int argc, char *argv[])
 	int		use_bsize;
 	char		*newpath;
 	int		pathlen = sizeof(PATH_SET) + 1;
+	struct device_param dev_param;
 
 	if (oldpath)
 		pathlen += strlen(oldpath);
@@ -2307,17 +2312,35 @@ profile_error:
 	}
 
 #ifdef HAVE_BLKID_PROBE_GET_TOPOLOGY
-	retval = get_device_geometry(device_name, &fs_param,
-				     (unsigned int) psector_size);
+	retval = get_device_geometry(device_name, blocksize,
+				     psector_size, &dev_param);
 	if (retval < 0) {
 		fprintf(stderr,
 			_("warning: Unable to get device geometry for %s\n"),
 			device_name);
-	} else if (retval) {
-		printf(_("%s alignment is offset by %lu bytes.\n"),
-		       device_name, retval);
-		printf(_("This may result in very poor performance, "
-			  "(re)-partitioning suggested.\n"));
+	} else {
+		/* setting stripe/stride to blocksize is pointless */
+		if (dev_param.min_io > blocksize)
+			fs_param.s_raid_stride = dev_param.min_io / blocksize;
+		if (dev_param.opt_io > blocksize) {
+			fs_param.s_raid_stripe_width =
+						dev_param.opt_io / blocksize;
+		}
+
+		if (dev_param.alignment_offset) {
+			printf(_("%s alignment is offset by %lu bytes.\n"),
+			       device_name, dev_param.alignment_offset);
+			printf(_("This may result in very poor performance, "
+				  "(re)-partitioning suggested.\n"));
+		}
+
+		if (dev_param.dax && blocksize != sys_page_size) {
+			fprintf(stderr,
+				_("%s is capable of DAX but current block size "
+				  "%u is different from system page size %u so "
+				  "filesystem will not support DAX.\n"),
+				device_name, blocksize, sys_page_size);
+		}
 	}
 #endif
 
-- 
2.16.4


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