[PATCH v1] fs/jfs: Switch to use new generic UUID API

[PATCH v1] fs/jfs: Switch to use new generic UUID API

[Andy Shevchenko]

There are new types and helpers that are supposed to be used in new code.

As a preparation to get rid of legacy types and API functions do
the conversion here.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
---

- not tested on real FS

 fs/jfs/jfs_incore.h     |  6 ++++--
 fs/jfs/jfs_logmgr.c     | 17 ++++++++---------
 fs/jfs/jfs_logmgr.h     | 10 +++++-----
 fs/jfs/jfs_mount.c      |  4 ++--
 fs/jfs/jfs_superblock.h |  7 ++++---
 fs/jfs/super.c          |  5 +++--
 6 files changed, 26 insertions(+), 23 deletions(-)

diff --git a/fs/jfs/jfs_incore.h b/fs/jfs/jfs_incore.h
index 912a3af2393e..340eb8e4f716 100644
--- a/fs/jfs/jfs_incore.h
+++ b/fs/jfs/jfs_incore.h
@@ -23,6 +23,8 @@
 #include <linux/rwsem.h>
 #include <linux/slab.h>
 #include <linux/bitops.h>
+#include <linux/uuid.h>
+
 #include "jfs_types.h"
 #include "jfs_xtree.h"
 #include "jfs_dtree.h"
@@ -178,8 +180,8 @@ struct jfs_sb_info {
 	pxd_t		logpxd;		/* pxd describing log	*/
 	pxd_t		fsckpxd;	/* pxd describing fsck wkspc */
 	pxd_t		ait2;		/* pxd describing AIT copy	*/
-	char		uuid[16];	/* 128-bit uuid for volume	*/
-	char		loguuid[16];	/* 128-bit uuid for log	*/
+	uuid_t		uuid;		/* 128-bit uuid for volume	*/
+	uuid_t		loguuid;	/* 128-bit uuid for log	*/
 	/*
 	 * commit_state is used for synchronization of the jfs_commit
 	 * threads.  It is protected by LAZY_LOCK().
diff --git a/fs/jfs/jfs_logmgr.c b/fs/jfs/jfs_logmgr.c
index 6b68df395892..6361fa4d85db 100644
--- a/fs/jfs/jfs_logmgr.c
+++ b/fs/jfs/jfs_logmgr.c
@@ -1092,8 +1092,7 @@ int lmLogOpen(struct super_block *sb)
 	mutex_lock(&jfs_log_mutex);
 	list_for_each_entry(log, &jfs_external_logs, journal_list) {
 		if (log->bdev->bd_dev == sbi->logdev) {
-			if (memcmp(log->uuid, sbi->loguuid,
-				   sizeof(log->uuid))) {
+			if (!uuid_equal(&log->uuid, &sbi->loguuid)) {
 				jfs_warn("wrong uuid on JFS journal");
 				mutex_unlock(&jfs_log_mutex);
 				return -EINVAL;
@@ -1130,7 +1129,7 @@ int lmLogOpen(struct super_block *sb)
 	}
 
 	log->bdev = bdev;
-	memcpy(log->uuid, sbi->loguuid, sizeof(log->uuid));
+	uuid_copy(&log->uuid, &sbi->loguuid);
 
 	/*
 	 * initialize log:
@@ -1336,7 +1335,7 @@ int lmLogInit(struct jfs_log * log)
 			jfs_info("lmLogInit: inline log:0x%p base:0x%Lx size:0x%x",
 				 log, (unsigned long long)log->base, log->size);
 		} else {
-			if (memcmp(logsuper->uuid, log->uuid, 16)) {
+			if (!uuid_equal(&logsuper->uuid, &log->uuid)) {
 				jfs_warn("wrong uuid on JFS log device");
 				goto errout20;
 			}
@@ -1732,7 +1731,7 @@ static int lmLogFileSystem(struct jfs_log * log, struct jfs_sb_info *sbi,
 	int i;
 	struct logsuper *logsuper;
 	struct lbuf *bpsuper;
-	char *uuid = sbi->uuid;
+	uuid_t *uuid = &sbi->uuid;
 
 	/*
 	 * insert/remove file system device to log active file system list.
@@ -1743,8 +1742,8 @@ static int lmLogFileSystem(struct jfs_log * log, struct jfs_sb_info *sbi,
 	logsuper = (struct logsuper *) bpsuper->l_ldata;
 	if (activate) {
 		for (i = 0; i < MAX_ACTIVE; i++)
-			if (!memcmp(logsuper->active[i].uuid, NULL_UUID, 16)) {
-				memcpy(logsuper->active[i].uuid, uuid, 16);
+			if (uuid_is_null(&logsuper->active[i].uuid)) {
+				uuid_copy(&logsuper->active[i].uuid, uuid);
 				sbi->aggregate = i;
 				break;
 			}
@@ -1755,8 +1754,8 @@ static int lmLogFileSystem(struct jfs_log * log, struct jfs_sb_info *sbi,
 		}
 	} else {
 		for (i = 0; i < MAX_ACTIVE; i++)
-			if (!memcmp(logsuper->active[i].uuid, uuid, 16)) {
-				memcpy(logsuper->active[i].uuid, NULL_UUID, 16);
+			if (uuid_equal(&logsuper->active[i].uuid, uuid)) {
+				uuid_copy(&logsuper->active[i].uuid, &uuid_null);
 				break;
 			}
 		if (i == MAX_ACTIVE) {
diff --git a/fs/jfs/jfs_logmgr.h b/fs/jfs/jfs_logmgr.h
index e38c21598850..870fc22360e7 100644
--- a/fs/jfs/jfs_logmgr.h
+++ b/fs/jfs/jfs_logmgr.h
@@ -19,6 +19,8 @@
 #ifndef	_H_JFS_LOGMGR
 #define _H_JFS_LOGMGR
 
+#include <linux/uuid.h>
+
 #include "jfs_filsys.h"
 #include "jfs_lock.h"
 
@@ -73,15 +75,13 @@ struct logsuper {
 	__le32 state;		/* 4: state - see below */
 
 	__le32 end;		/* 4: addr of last log record set by logredo */
-	char uuid[16];		/* 16: 128-bit journal uuid */
+	uuid_t uuid;		/* 16: 128-bit journal uuid */
 	char label[16];		/* 16: journal label */
 	struct {
-		char uuid[16];
+		uuid_t uuid;
 	} active[MAX_ACTIVE];	/* 2048: active file systems list */
 };
 
-#define NULL_UUID "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"
-
 /* log flag: commit option (see jfs_filsys.h) */
 
 /* log state */
@@ -410,7 +410,7 @@ struct jfs_log {
 	spinlock_t synclock;	/* 4: synclist lock */
 	struct lbuf *wqueue;	/* 4: log pageout queue */
 	int count;		/* 4: count */
-	char uuid[16];		/* 16: 128-bit uuid of log device */
+	uuid_t uuid;		/* 16: 128-bit uuid of log device */
 
 	int no_integrity;	/* 3: flag to disable journaling to disk */
 };
diff --git a/fs/jfs/jfs_mount.c b/fs/jfs/jfs_mount.c
index d8658607bf46..c9c1f16b93df 100644
--- a/fs/jfs/jfs_mount.c
+++ b/fs/jfs/jfs_mount.c
@@ -389,8 +389,8 @@ static int chkSuper(struct super_block *sb)
 		sbi->logpxd = j_sb->s_logpxd;
 	else {
 		sbi->logdev = new_decode_dev(le32_to_cpu(j_sb->s_logdev));
-		memcpy(sbi->uuid, j_sb->s_uuid, sizeof(sbi->uuid));
-		memcpy(sbi->loguuid, j_sb->s_loguuid, sizeof(sbi->uuid));
+		uuid_copy(&sbi->uuid, &j_sb->s_uuid);
+		uuid_copy(&sbi->loguuid, &j_sb->s_loguuid);
 	}
 	sbi->fsckpxd = j_sb->s_fsckpxd;
 	sbi->ait2 = j_sb->s_ait2;
diff --git a/fs/jfs/jfs_superblock.h b/fs/jfs/jfs_superblock.h
index 04847b8d3070..0a401f083d1a 100644
--- a/fs/jfs/jfs_superblock.h
+++ b/fs/jfs/jfs_superblock.h
@@ -18,6 +18,8 @@
 #ifndef	_H_JFS_SUPERBLOCK
 #define _H_JFS_SUPERBLOCK
 
+#include <linux/uuid.h>
+
 /*
  * make the magic number something a human could read
  */
@@ -100,10 +102,9 @@ struct jfs_superblock {
 	pxd_t s_xlogpxd;	/* 8: extendfs logpxd */
 	/* - 128 byte boundary - */
 
-	char s_uuid[16];	/* 16: 128-bit uuid for volume */
+	uuid_t s_uuid;		/* 16: 128-bit uuid for volume */
 	char s_label[16];	/* 16: volume label */
-	char s_loguuid[16];	/* 16: 128-bit uuid for log device */
-
+	uuid_t s_loguuid;	/* 16: 128-bit uuid for log device */
 };
 
 extern int readSuper(struct super_block *, struct buffer_head **);
diff --git a/fs/jfs/super.c b/fs/jfs/super.c
index 65d8fc87ab11..99a43e7f6ee0 100644
--- a/fs/jfs/super.c
+++ b/fs/jfs/super.c
@@ -174,8 +174,9 @@ static int jfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 	buf->f_files = maxinodes;
 	buf->f_ffree = maxinodes - (atomic_read(&imap->im_numinos) -
 				    atomic_read(&imap->im_numfree));
-	buf->f_fsid.val[0] = (u32)crc32_le(0, sbi->uuid, sizeof(sbi->uuid)/2);
-	buf->f_fsid.val[1] = (u32)crc32_le(0, sbi->uuid + sizeof(sbi->uuid)/2,
+	buf->f_fsid.val[0] = (u32)crc32_le(0, (char *)&sbi->uuid,
+					sizeof(sbi->uuid)/2);
+	buf->f_fsid.val[1] = (u32)crc32_le(0, (char *)&sbi->uuid + sizeof(sbi->uuid)/2,
 					sizeof(sbi->uuid)/2);
 
 	buf->f_namelen = JFS_NAME_MAX;
-- 
2.20.1

Re: [PATCH v1] fs/jfs: Switch to use new generic UUID API

[Dave Kleikamp]

On 1/10/19 7:41 AM, Andy Shevchenko wrote:
> There are new types and helpers that are supposed to be used in new code.
> 
> As a preparation to get rid of legacy types and API functions do
> the conversion here.

Looks good to me. I tweaked it slightly to keep checkpatch from
complaining about lines over 80 characters. I'll push it into -next for
v5.1.

Shaggy

> 
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
> 
> - not tested on real FS
> 
>  fs/jfs/jfs_incore.h     |  6 ++++--
>  fs/jfs/jfs_logmgr.c     | 17 ++++++++---------
>  fs/jfs/jfs_logmgr.h     | 10 +++++-----
>  fs/jfs/jfs_mount.c      |  4 ++--
>  fs/jfs/jfs_superblock.h |  7 ++++---
>  fs/jfs/super.c          |  5 +++--
>  6 files changed, 26 insertions(+), 23 deletions(-)
> 
> diff --git a/fs/jfs/jfs_incore.h b/fs/jfs/jfs_incore.h
> index 912a3af2393e..340eb8e4f716 100644
> --- a/fs/jfs/jfs_incore.h
> +++ b/fs/jfs/jfs_incore.h
> @@ -23,6 +23,8 @@
>  #include <linux/rwsem.h>
>  #include <linux/slab.h>
>  #include <linux/bitops.h>
> +#include <linux/uuid.h>
> +
>  #include "jfs_types.h"
>  #include "jfs_xtree.h"
>  #include "jfs_dtree.h"
> @@ -178,8 +180,8 @@ struct jfs_sb_info {
>  	pxd_t		logpxd;		/* pxd describing log	*/
>  	pxd_t		fsckpxd;	/* pxd describing fsck wkspc */
>  	pxd_t		ait2;		/* pxd describing AIT copy	*/
> -	char		uuid[16];	/* 128-bit uuid for volume	*/
> -	char		loguuid[16];	/* 128-bit uuid for log	*/
> +	uuid_t		uuid;		/* 128-bit uuid for volume	*/
> +	uuid_t		loguuid;	/* 128-bit uuid for log	*/
>  	/*
>  	 * commit_state is used for synchronization of the jfs_commit
>  	 * threads.  It is protected by LAZY_LOCK().
> diff --git a/fs/jfs/jfs_logmgr.c b/fs/jfs/jfs_logmgr.c
> index 6b68df395892..6361fa4d85db 100644
> --- a/fs/jfs/jfs_logmgr.c
> +++ b/fs/jfs/jfs_logmgr.c
> @@ -1092,8 +1092,7 @@ int lmLogOpen(struct super_block *sb)
>  	mutex_lock(&jfs_log_mutex);
>  	list_for_each_entry(log, &jfs_external_logs, journal_list) {
>  		if (log->bdev->bd_dev == sbi->logdev) {
> -			if (memcmp(log->uuid, sbi->loguuid,
> -				   sizeof(log->uuid))) {
> +			if (!uuid_equal(&log->uuid, &sbi->loguuid)) {
>  				jfs_warn("wrong uuid on JFS journal");
>  				mutex_unlock(&jfs_log_mutex);
>  				return -EINVAL;
> @@ -1130,7 +1129,7 @@ int lmLogOpen(struct super_block *sb)
>  	}
>  
>  	log->bdev = bdev;
> -	memcpy(log->uuid, sbi->loguuid, sizeof(log->uuid));
> +	uuid_copy(&log->uuid, &sbi->loguuid);
>  
>  	/*
>  	 * initialize log:
> @@ -1336,7 +1335,7 @@ int lmLogInit(struct jfs_log * log)
>  			jfs_info("lmLogInit: inline log:0x%p base:0x%Lx size:0x%x",
>  				 log, (unsigned long long)log->base, log->size);
>  		} else {
> -			if (memcmp(logsuper->uuid, log->uuid, 16)) {
> +			if (!uuid_equal(&logsuper->uuid, &log->uuid)) {
>  				jfs_warn("wrong uuid on JFS log device");
>  				goto errout20;
>  			}
> @@ -1732,7 +1731,7 @@ static int lmLogFileSystem(struct jfs_log * log, struct jfs_sb_info *sbi,
>  	int i;
>  	struct logsuper *logsuper;
>  	struct lbuf *bpsuper;
> -	char *uuid = sbi->uuid;
> +	uuid_t *uuid = &sbi->uuid;
>  
>  	/*
>  	 * insert/remove file system device to log active file system list.
> @@ -1743,8 +1742,8 @@ static int lmLogFileSystem(struct jfs_log * log, struct jfs_sb_info *sbi,
>  	logsuper = (struct logsuper *) bpsuper->l_ldata;
>  	if (activate) {
>  		for (i = 0; i < MAX_ACTIVE; i++)
> -			if (!memcmp(logsuper->active[i].uuid, NULL_UUID, 16)) {
> -				memcpy(logsuper->active[i].uuid, uuid, 16);
> +			if (uuid_is_null(&logsuper->active[i].uuid)) {
> +				uuid_copy(&logsuper->active[i].uuid, uuid);
>  				sbi->aggregate = i;
>  				break;
>  			}
> @@ -1755,8 +1754,8 @@ static int lmLogFileSystem(struct jfs_log * log, struct jfs_sb_info *sbi,
>  		}
>  	} else {
>  		for (i = 0; i < MAX_ACTIVE; i++)
> -			if (!memcmp(logsuper->active[i].uuid, uuid, 16)) {
> -				memcpy(logsuper->active[i].uuid, NULL_UUID, 16);
> +			if (uuid_equal(&logsuper->active[i].uuid, uuid)) {
> +				uuid_copy(&logsuper->active[i].uuid, &uuid_null);
>  				break;
>  			}
>  		if (i == MAX_ACTIVE) {
> diff --git a/fs/jfs/jfs_logmgr.h b/fs/jfs/jfs_logmgr.h
> index e38c21598850..870fc22360e7 100644
> --- a/fs/jfs/jfs_logmgr.h
> +++ b/fs/jfs/jfs_logmgr.h
> @@ -19,6 +19,8 @@
>  #ifndef	_H_JFS_LOGMGR
>  #define _H_JFS_LOGMGR
>  
> +#include <linux/uuid.h>
> +
>  #include "jfs_filsys.h"
>  #include "jfs_lock.h"
>  
> @@ -73,15 +75,13 @@ struct logsuper {
>  	__le32 state;		/* 4: state - see below */
>  
>  	__le32 end;		/* 4: addr of last log record set by logredo */
> -	char uuid[16];		/* 16: 128-bit journal uuid */
> +	uuid_t uuid;		/* 16: 128-bit journal uuid */
>  	char label[16];		/* 16: journal label */
>  	struct {
> -		char uuid[16];
> +		uuid_t uuid;
>  	} active[MAX_ACTIVE];	/* 2048: active file systems list */
>  };
>  
> -#define NULL_UUID "\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0"
> -
>  /* log flag: commit option (see jfs_filsys.h) */
>  
>  /* log state */
> @@ -410,7 +410,7 @@ struct jfs_log {
>  	spinlock_t synclock;	/* 4: synclist lock */
>  	struct lbuf *wqueue;	/* 4: log pageout queue */
>  	int count;		/* 4: count */
> -	char uuid[16];		/* 16: 128-bit uuid of log device */
> +	uuid_t uuid;		/* 16: 128-bit uuid of log device */
>  
>  	int no_integrity;	/* 3: flag to disable journaling to disk */
>  };
> diff --git a/fs/jfs/jfs_mount.c b/fs/jfs/jfs_mount.c
> index d8658607bf46..c9c1f16b93df 100644
> --- a/fs/jfs/jfs_mount.c
> +++ b/fs/jfs/jfs_mount.c
> @@ -389,8 +389,8 @@ static int chkSuper(struct super_block *sb)
>  		sbi->logpxd = j_sb->s_logpxd;
>  	else {
>  		sbi->logdev = new_decode_dev(le32_to_cpu(j_sb->s_logdev));
> -		memcpy(sbi->uuid, j_sb->s_uuid, sizeof(sbi->uuid));
> -		memcpy(sbi->loguuid, j_sb->s_loguuid, sizeof(sbi->uuid));
> +		uuid_copy(&sbi->uuid, &j_sb->s_uuid);
> +		uuid_copy(&sbi->loguuid, &j_sb->s_loguuid);
>  	}
>  	sbi->fsckpxd = j_sb->s_fsckpxd;
>  	sbi->ait2 = j_sb->s_ait2;
> diff --git a/fs/jfs/jfs_superblock.h b/fs/jfs/jfs_superblock.h
> index 04847b8d3070..0a401f083d1a 100644
> --- a/fs/jfs/jfs_superblock.h
> +++ b/fs/jfs/jfs_superblock.h
> @@ -18,6 +18,8 @@
>  #ifndef	_H_JFS_SUPERBLOCK
>  #define _H_JFS_SUPERBLOCK
>  
> +#include <linux/uuid.h>
> +
>  /*
>   * make the magic number something a human could read
>   */
> @@ -100,10 +102,9 @@ struct jfs_superblock {
>  	pxd_t s_xlogpxd;	/* 8: extendfs logpxd */
>  	/* - 128 byte boundary - */
>  
> -	char s_uuid[16];	/* 16: 128-bit uuid for volume */
> +	uuid_t s_uuid;		/* 16: 128-bit uuid for volume */
>  	char s_label[16];	/* 16: volume label */
> -	char s_loguuid[16];	/* 16: 128-bit uuid for log device */
> -
> +	uuid_t s_loguuid;	/* 16: 128-bit uuid for log device */
>  };
>  
>  extern int readSuper(struct super_block *, struct buffer_head **);
> diff --git a/fs/jfs/super.c b/fs/jfs/super.c
> index 65d8fc87ab11..99a43e7f6ee0 100644
> --- a/fs/jfs/super.c
> +++ b/fs/jfs/super.c
> @@ -174,8 +174,9 @@ static int jfs_statfs(struct dentry *dentry, struct kstatfs *buf)
>  	buf->f_files = maxinodes;
>  	buf->f_ffree = maxinodes - (atomic_read(&imap->im_numinos) -
>  				    atomic_read(&imap->im_numfree));
> -	buf->f_fsid.val[0] = (u32)crc32_le(0, sbi->uuid, sizeof(sbi->uuid)/2);
> -	buf->f_fsid.val[1] = (u32)crc32_le(0, sbi->uuid + sizeof(sbi->uuid)/2,
> +	buf->f_fsid.val[0] = (u32)crc32_le(0, (char *)&sbi->uuid,
> +					sizeof(sbi->uuid)/2);
> +	buf->f_fsid.val[1] = (u32)crc32_le(0, (char *)&sbi->uuid + sizeof(sbi->uuid)/2,
>  					sizeof(sbi->uuid)/2);
>  
>  	buf->f_namelen = JFS_NAME_MAX;
> 

Re: [PATCH v1] fs/jfs: Switch to use new generic UUID API

[Christoph Hellwig]

> +	buf->f_fsid.val[1] = (u32)crc32_le(0, (char *)&sbi->uuid + sizeof(sbi->uuid)/2,

This adds an overly long line, and has weird operator spacing.

In fact given how much deep magic it does it should probably be moved
into a helper and properly documented when you touch it anyway.

Re: [PATCH v1] fs/jfs: Switch to use new generic UUID API

[Dave Kleikamp]

On 1/21/19 2:49 AM, Christoph Hellwig wrote:
>> +	buf->f_fsid.val[1] = (u32)crc32_le(0, (char *)&sbi->uuid + sizeof(sbi->uuid)/2,
> 
> This adds an overly long line, and has weird operator spacing.
> 
> In fact given how much deep magic it does it should probably be moved
> into a helper and properly documented when you touch it anyway.
> 

I cleaned this up a bit when I pushed it to the jfs tree.

https://github.com/kleikamp/linux-shaggy/commit/2e3bc6125154c691e987e2554f2c99ec10f83b73

Here's the relevant part. It's still a bit ugly, but I got rid of an
unnecessary cast and kept the lines from exceeding 80 characters.

diff --git a/fs/jfs/super.c b/fs/jfs/super.c
index 65d8fc87ab11..c15ff56a8516 100644
--- a/fs/jfs/super.c
+++ b/fs/jfs/super.c
@@ -174,9 +174,11 @@ static int jfs_statfs(struct dentry *dentry, struct kstatfs *buf)
 	buf->f_files = maxinodes;
 	buf->f_ffree = maxinodes - (atomic_read(&imap->im_numinos) -
 				    atomic_read(&imap->im_numfree));
-	buf->f_fsid.val[0] = (u32)crc32_le(0, sbi->uuid, sizeof(sbi->uuid)/2);
-	buf->f_fsid.val[1] = (u32)crc32_le(0, sbi->uuid + sizeof(sbi->uuid)/2,
-					sizeof(sbi->uuid)/2);
+	buf->f_fsid.val[0] = crc32_le(0, (char *)&sbi->uuid,
+				      sizeof(sbi->uuid)/2);
+	buf->f_fsid.val[1] = crc32_le(0,
+				      (char *)&sbi->uuid + sizeof(sbi->uuid)/2,
+				      sizeof(sbi->uuid)/2);
 
 	buf->f_namelen = JFS_NAME_MAX;
 	return 0;

Re: [PATCH v1] fs/jfs: Switch to use new generic UUID API

[Christoph Hellwig]

On Mon, Jan 21, 2019 at 10:19:15AM -0600, Dave Kleikamp wrote:
> diff --git a/fs/jfs/super.c b/fs/jfs/super.c
> index 65d8fc87ab11..c15ff56a8516 100644
> --- a/fs/jfs/super.c
> +++ b/fs/jfs/super.c
> @@ -174,9 +174,11 @@ static int jfs_statfs(struct dentry *dentry, struct kstatfs *buf)
>  	buf->f_files = maxinodes;
>  	buf->f_ffree = maxinodes - (atomic_read(&imap->im_numinos) -
>  				    atomic_read(&imap->im_numfree));
> -	buf->f_fsid.val[0] = (u32)crc32_le(0, sbi->uuid, sizeof(sbi->uuid)/2);
> -	buf->f_fsid.val[1] = (u32)crc32_le(0, sbi->uuid + sizeof(sbi->uuid)/2,
> -					sizeof(sbi->uuid)/2);
> +	buf->f_fsid.val[0] = crc32_le(0, (char *)&sbi->uuid,
> +				      sizeof(sbi->uuid)/2);
> +	buf->f_fsid.val[1] = crc32_le(0,
> +				      (char *)&sbi->uuid + sizeof(sbi->uuid)/2,
> +				      sizeof(sbi->uuid)/2);

I'd really love to see a little helper to calculate the fsid, and
a comment on that function documenting the design decision behind it.

Re: [PATCH v1] fs/jfs: Switch to use new generic UUID API

[Dave Kleikamp]

On 1/21/19 10:23 AM, Christoph Hellwig wrote:
> On Mon, Jan 21, 2019 at 10:19:15AM -0600, Dave Kleikamp wrote:
>> diff --git a/fs/jfs/super.c b/fs/jfs/super.c
>> index 65d8fc87ab11..c15ff56a8516 100644
>> --- a/fs/jfs/super.c
>> +++ b/fs/jfs/super.c
>> @@ -174,9 +174,11 @@ static int jfs_statfs(struct dentry *dentry, struct kstatfs *buf)
>>  	buf->f_files = maxinodes;
>>  	buf->f_ffree = maxinodes - (atomic_read(&imap->im_numinos) -
>>  				    atomic_read(&imap->im_numfree));
>> -	buf->f_fsid.val[0] = (u32)crc32_le(0, sbi->uuid, sizeof(sbi->uuid)/2);
>> -	buf->f_fsid.val[1] = (u32)crc32_le(0, sbi->uuid + sizeof(sbi->uuid)/2,
>> -					sizeof(sbi->uuid)/2);
>> +	buf->f_fsid.val[0] = crc32_le(0, (char *)&sbi->uuid,
>> +				      sizeof(sbi->uuid)/2);
>> +	buf->f_fsid.val[1] = crc32_le(0,
>> +				      (char *)&sbi->uuid + sizeof(sbi->uuid)/2,
>> +				      sizeof(sbi->uuid)/2);
> 
> I'd really love to see a little helper to calculate the fsid, and
> a comment on that function documenting the design decision behind it.

I can do that. It was a long time ago, but I'm sure the design decision
was that I took the idea from another filesystem, possibly reiserfs, but
I'll make a better case than that. :-)

Shaggy