Re: [PATCH 4/5] FAT: notify userspace of fs errors with uevents

[Denis Karpov <ext-denis.2.karpov@nokia.com>]

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On Thu, Jun 11, 2009 at 02:24:48PM +0200, Karpov Denis.2 (EXT-Teleca/Helsinki) wrote:
> Add mechnism to optionally notify userspace about fs errors with
> uevents associated with fs kobject's attribute:
> 	/sys/fs/fat/<part_bdev>/fs_fault
> 
> uevent's type is KOBJ_CHANGE, uevent's environment variable FS_FAULT=1.

As Jan and Artem pointed out in the earlier thread, 'notify' mount option 
that would make fs use this mechanism doesn't make much sense.
So, send notification uevents unconditionally, fixed patch is attached
(nevermind patch5/5).

Denis

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>From 5e3bd63625ae5de61676e9bb1fe6f04582fef936 Mon Sep 17 00:00:00 2001
From: Denis Karpov <ext-denis.2.karpov@nokia.com>
Date: Thu, 11 Jun 2009 07:25:52 -0400
Subject: [PATCH] FAT: notify userspace of fs errors with uevents

Make FAT notify userspace about fs errors with uevents associated
with fs kobject's attribute:
	/sys/fs/fat/<part_bdev>/fs_fault

uevent's type is KOBJ_CHANGE, uevent's environment variable FS_FAULT=1.

Signed-off-by: Denis Karpov <ext-denis.2.karpov@nokia.com>
---
 fs/fat/fat.h   |    6 +++---
 fs/fat/inode.c |   37 +++++++++++++++++++++++++++++++------
 fs/fat/misc.c  |    4 ++--
 3 files changed, 36 insertions(+), 11 deletions(-)

diff --git a/fs/fat/fat.h b/fs/fat/fat.h
index 480be11..ebf4c62 100644
--- a/fs/fat/fat.h
+++ b/fs/fat/fat.h
@@ -87,9 +87,9 @@ struct msdos_sb_info {
 #define FAT_CACHE_VALID	0	/* special case for valid cache */
 
 /* Mark FAT run-time errors  */
-#define FAT_FS_FAULT_SET(sbi, val) \
+#define FAT_FS_FAULT_SET(sbi, val, notify) \
 	fat_sbi_attr_set_notify(sbi, offsetof(struct msdos_sb_info, fs_fault), \
-				val)
+				val, notify)
 
 /*
  * MS-DOS file system inode data in memory
@@ -320,7 +320,7 @@ extern int fat_fill_super(struct super_block *sb, void *data, int silent,
 extern int fat_flush_inodes(struct super_block *sb, struct inode *i1,
 		            struct inode *i2);
 extern int fat_sbi_attr_set_notify(struct msdos_sb_info *sbi,
-			unsigned long offset, unsigned long val);
+			unsigned long offset, unsigned long val, int notify);
 
 /* fat/misc.c */
 extern void fat_fs_error(struct super_block *s, const char *function,
diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index 4613343..b1a0c8d 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -527,7 +527,7 @@ static int fat_remount(struct super_block *sb, int *flags, char *data)
 {
 	struct msdos_sb_info *sbi = MSDOS_SB(sb);
 	*flags |= MS_NODIRATIME | (sbi->options.isvfat ? 0 : MS_NOATIME);
-	FAT_FS_FAULT_SET(sbi, 0);
+	FAT_FS_FAULT_SET(sbi, 0, 0);
 	return 0;
 }
 
@@ -1185,6 +1185,7 @@ struct fat_attr {
 	ssize_t (*store)(struct fat_attr *, struct msdos_sb_info *,
 			 const char *, size_t);
 	unsigned short offset;
+	unsigned short uevent;
 };
 
 static ssize_t fat_sbi_attr_show(struct fat_attr *a, struct msdos_sb_info *sbi,
@@ -1206,17 +1207,22 @@ static ssize_t fat_sbi_attr_store(struct fat_attr *a,
 	return count;
 }
 
-#define FAT_SBI_ATTR(_name, _mode, _show, _store) \
+#define FAT_SBI_ATTR(_name, _mode, _show, _store, _uevent) \
 static struct fat_attr fat_attr_##_name = {			\
 	.attr = {.name = __stringify(_name), .mode = _mode },	\
 	.show	= _show,					\
 	.store	= _store,					\
 	.offset = offsetof(struct msdos_sb_info, _name),	\
+	.uevent = _uevent,					\
 }
 #define FAT_SBI_RO_ATTR(name) FAT_SBI_ATTR(name, 0444, \
-				fat_sbi_attr_show, NULL)
+				fat_sbi_attr_show, NULL, 0)
 #define FAT_SBI_RW_ATTR(name) FAT_SBI_ATTR(name, 0644 \
-				fat_sbi_attr_show, fat_sbi_attr_store)
+				fat_sbi_attr_show, fat_sbi_attr_store, 0)
+#define FAT_SBI_RO_ATTR_NOTIFY(name) FAT_SBI_ATTR(name, 0444, \
+				fat_sbi_attr_show, NULL, 1)
+#define FAT_SBI_RW_ATTR_NOTIFY(name) FAT_SBI_ATTR(name, 0644, \
+				fat_sbi_attr_show, fat_sbi_attr_store, 1)
 
 #define ATTR_LIST(name) (&fat_attr_ ##name.attr)
 
@@ -1240,11 +1246,15 @@ static struct attribute *find_attr_by_offset(struct kobject *kobj,
 
 int fat_sbi_attr_set_notify(struct msdos_sb_info *sbi,
 			unsigned long offset,
-			unsigned long val)
+			unsigned long val,
+			int notify)
 {
 	struct fat_attr *a =
 		(struct fat_attr *) find_attr_by_offset(&sbi->s_kobj, offset);
 	unsigned long *attr_val;
+	int ev_len;
+	char *t_str;
+	char *envp[] = { NULL, NULL };
 
 	if (!a)
 		return -EINVAL;
@@ -1257,6 +1267,21 @@ int fat_sbi_attr_set_notify(struct msdos_sb_info *sbi,
 
 	sysfs_notify(&sbi->s_kobj, NULL, a->attr.name);
 
+	if (!notify || !a->uevent)
+		return 0;
+
+	/* dec MAX_UINT == 10 char string */
+	ev_len = strlen(a->attr.name) + 1 + 10 + 1;
+	envp[0] = t_str = kzalloc(ev_len, GFP_KERNEL);
+	if (!t_str)
+		return -ENOMEM;
+
+	snprintf(t_str, ev_len, "%s=%lu", a->attr.name, val);
+	while ((*t_str++ = toupper(*t_str)))
+		;
+	kobject_uevent_env(&sbi->s_kobj, KOBJ_CHANGE, envp);
+	kfree(envp[0]);
+
 	return 0;
 }
 EXPORT_SYMBOL(fat_sbi_attr_set_notify);
@@ -1573,7 +1598,7 @@ int fat_fill_super(struct super_block *sb, void *data, int silent,
 		printk(KERN_ERR "FAT: create fs kobject failed\n");
 		goto out_fail;
 	}
-	FAT_FS_FAULT_SET(sbi, 0);
+	FAT_FS_FAULT_SET(sbi, 0, 0);
 
 	return 0;
 
diff --git a/fs/fat/misc.c b/fs/fat/misc.c
index ce478be..236e021 100644
--- a/fs/fat/misc.c
+++ b/fs/fat/misc.c
@@ -35,7 +35,7 @@ void fat_fs_error(struct super_block *s, const char *function,
 		printk(KERN_ERR "    File system has been set read-only\n");
 	}
 
-	FAT_FS_FAULT_SET(sbi, 1);
+	FAT_FS_FAULT_SET(sbi, 1, 1);
 }
 EXPORT_SYMBOL_GPL(fat_fs_error);
 
@@ -58,7 +58,7 @@ void fat_fs_warning(struct super_block *s, const char * function,
 	printk("\n");
 	va_end(args);
 
-	FAT_FS_FAULT_SET(sbi, 1);
+	FAT_FS_FAULT_SET(sbi, 1, 1);
 }
 EXPORT_SYMBOL_GPL(fat_fs_warning);
 
-- 
1.6.3.1