Swap Questions (includes possible bug) - swapfile.c / swap.c

diff -r -u -P -x CVS -x *,v 2.2.6/drivers/block/ll_rw_blk.c current/drivers/block/ll_rw_blk.c
@@ -16,6 +16,7 @@
 #include <linux/config.h>
 #include <linux/locks.h>
 #include <linux/mm.h>
+#include <linux/slab.h>
 #include <linux/init.h>
 
 #include <asm/system.h>

@@ -241,8 +242,24 @@
 }
 
 /* RO fail safe mechanism */
+/* device busy: (C) Manfred Spraul [email protected] */
 
-static long ro_bits[MAX_BLKDEV][8];
+struct kdev_bits {
+	unsigned char ro_bits[(1U << MINORBITS)/8];
+	unsigned char busy_bits[(1U << MINORBITS)/8];
+};
+
+static struct kdev_bits* kdev_info[MAX_BLKDEV] = { NULL, NULL };
+
+#define ALLOC_KDEV_BITS(major) \
+	if (kdev_info[major] == NULL) { \
+		kdev_info[major] = kmalloc(sizeof(struct kdev_bits),GFP_KERNEL); \
+		if(kdev_info[major] == NULL) { \
+			printk("ALLOC_KDEV_BITS() failed due to ENOMEM.\n"); \
+			return; \
+		} \
+		memset(kdev_info[major],0,sizeof(struct kdev_bits)); \
+	}
 
 int is_read_only(kdev_t dev)
 {

@@ -251,7 +268,8 @@
 	major = MAJOR(dev);
 	minor = MINOR(dev);
 	if (major < 0 || major >= MAX_BLKDEV) return 0;
-	return ro_bits[major][minor >> 5] & (1 << (minor & 31));
+	if (kdev_info[major] == NULL) return 0;
+     	return kdev_info[major]->ro_bits[minor >> 3] & (1 << (minor & 7));
 }
 
 void set_device_ro(kdev_t dev,int flag)

@@ -261,10 +279,39 @@
 	major = MAJOR(dev);
 	minor = MINOR(dev);
 	if (major < 0 || major >= MAX_BLKDEV) return;
-	if (flag) ro_bits[major][minor >> 5] |= 1 << (minor & 31);
-	else ro_bits[major][minor >> 5] &= ~(1 << (minor & 31));
+	ALLOC_KDEV_BITS(major)
+	if (flag)
+		kdev_info[major]->ro_bits[minor >> 3] |= 1 << (minor & 7);
+	 else
+		kdev_info[major]->ro_bits[minor >> 3] &= ~(1 << (minor & 7));
+}
+
+int is_device_busy(kdev_t dev)
+{
+	int minor,major;
+
+	major = MAJOR(dev);
+	minor = MINOR(dev);
+	if (major < 0 || major >= MAX_BLKDEV) return 0;
+	if (kdev_info[major] == NULL) return 0;
+	return kdev_info[major]->busy_bits[minor >> 3] & (1 << (minor & 7));
 }
 
+void set_device_busy(kdev_t dev,int flag)
+{
+	int minor,major;
+	
+	major = MAJOR(dev);
+	minor = MINOR(dev);
+	if (major < 0 || major >= MAX_BLKDEV) return;
+	ALLOC_KDEV_BITS(major)
+	if (flag)
+		kdev_info[major]->busy_bits[minor >> 3] |= 1 << (minor & 7);
+	 else
+		kdev_info[major]->busy_bits[minor >> 3] &= ~(1 << (minor & 7));
+}
+
+
 static inline void drive_stat_acct(int cmd, unsigned long nr_sectors,
                                    short disk_index)
 {

@@ -731,7 +778,6 @@
 		req->rq_status = RQ_INACTIVE;
 		req->next = NULL;
 	}
-	memset(ro_bits,0,sizeof(ro_bits));
 	memset(max_readahead, 0, sizeof(max_readahead));
 	memset(max_sectors, 0, sizeof(max_sectors));
 #ifdef CONFIG_AMIGA_Z2RAM

diff -r -u -P -x CVS -x *,v 2.2.6/fs/super.c current/fs/super.c
@@ -131,6 +131,7 @@
 		vfsmnttail->mnt_next = lptr;
 		vfsmnttail = lptr;
 	}
+	set_device_busy(sb->s_dev,1);
 out:
 	return lptr;
 }

@@ -165,6 +166,8 @@
 	kfree(tofree->mnt_devname);
 	kfree(tofree->mnt_dirname);
 	kfree_s(tofree, sizeof(struct vfsmount));
+
+	set_device_busy(dev,0);
 }
 
 int register_filesystem(struct file_system_type * fs)

@@ -873,6 +876,8 @@
 	if (dir_d->d_covers != dir_d)
 		goto dput_and_out;
 
+	if (is_device_busy(dev))
+		goto dput_and_out;
 	/*
 	 * Note: If the superblock already exists,
 	 * read_super just does a get_super().

diff -r -u -P -x CVS -x *,v 2.2.6/include/linux/fs.h current/include/linux/fs.h
@@ -839,6 +839,8 @@
 extern struct buffer_head * find_buffer(kdev_t dev, int block, int size);
 extern void ll_rw_block(int, int, struct buffer_head * bh[]);
 extern int is_read_only(kdev_t);
+extern int is_device_busy(kdev_t);
+extern void set_device_busy(kdev_t dev, int flag);
 extern void __brelse(struct buffer_head *);
 extern inline void brelse(struct buffer_head *buf)
 {

diff -r -u -P -x CVS -x *,v 2.2.6/kernel/ksyms.c current/kernel/ksyms.c
@@ -47,7 +47,7 @@
 #endif
 
 extern char *get_options(char *str, int *ints);
-extern void set_device_ro(kdev_t dev,int flag);
+extern void set_device_ro(kdev_t dev, int flag);
 extern struct file_operations * get_blkfops(unsigned int);
 extern int blkdev_release(struct inode * inode);
 #if !defined(CONFIG_NFSD) && defined(CONFIG_NFSD_MODULE)

@@ -209,6 +209,8 @@
 EXPORT_SYMBOL(blk_dev);
 EXPORT_SYMBOL(is_read_only);
 EXPORT_SYMBOL(set_device_ro);
+EXPORT_SYMBOL(is_device_busy);
+EXPORT_SYMBOL(set_device_busy);
 EXPORT_SYMBOL(bmap);
 EXPORT_SYMBOL(sync_dev);
 EXPORT_SYMBOL(get_blkfops);

diff -r -u -P -x CVS -x *,v 2.2.6/mm/swapfile.c current/mm/swapfile.c
@@ -414,6 +414,7 @@
 			filp.f_op->release(dentry->d_inode,&filp);
 			filp.f_op->release(dentry->d_inode,&filp);
 		}
+		set_device_busy(p->swap_device,0);
 	}
 	dput(dentry);
 

@@ -531,6 +532,10 @@
 
 	if (S_ISBLK(swap_dentry->d_inode->i_mode)) {
 		p->swap_device = swap_dentry->d_inode->i_rdev;
+		if(is_device_busy(p->swap_device)) {
+			error = -EBUSY;
+			goto bad_swap;
+		}
 		set_blocksize(p->swap_device, PAGE_SIZE);
 		
 		filp.f_dentry = swap_dentry;

@@ -686,6 +691,8 @@
 		swap_info[prev].next = p - swap_info;
 	}
 	error = 0;
+	if(p->swap_device != 0)
+		set_device_busy(p->swap_device,1);
 	goto out;
 bad_swap:
 	if(filp.f_op && filp.f_op->release)