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From:   Jan Kara <jack@suse.cz>
To:     Ted Tso <tytso@mit.edu>
Cc:     <linux-ext4@vger.kernel.org>, Jan Kara <jack@suse.cz>
Subject: [PATCH] mke2fs: Warn if fs block size is incompatible with DAX
Date:   Thu,  9 Jul 2020 16:40:57 +0200
Message-Id: <20200709144057.21333-1-jack@suse.cz>
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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