get rid of DEBUG_WRITECOUNT

it only makes control flow in __fput() and friends more convoluted.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

arch/powerpc/configs/ppc6xx_defconfig

@@ -1244,7 +1244,6 @@ CONFIG_DEBUG_SPINLOCK_SLEEP=y
 CONFIG_DEBUG_HIGHMEM=y
 CONFIG_DEBUG_INFO=y
 CONFIG_DEBUG_VM=y
-CONFIG_DEBUG_WRITECOUNT=y
 CONFIG_DEBUG_LIST=y
 CONFIG_DEBUG_SG=y
 # CONFIG_RCU_CPU_STALL_DETECTOR is not set

arch/powerpc/configs/ps3_defconfig

@@ -174,7 +174,6 @@ CONFIG_DETECT_HUNG_TASK=y
 CONFIG_PROVE_LOCKING=y
 CONFIG_DEBUG_LOCKDEP=y
 CONFIG_DEBUG_INFO=y
-CONFIG_DEBUG_WRITECOUNT=y
 CONFIG_DEBUG_MEMORY_INIT=y
 CONFIG_DEBUG_LIST=y
 CONFIG_RCU_CPU_STALL_TIMEOUT=60

arch/s390/configs/default_defconfig

@@ -550,7 +550,6 @@ CONFIG_LOCK_STAT=y
 CONFIG_DEBUG_LOCKDEP=y
 CONFIG_DEBUG_ATOMIC_SLEEP=y
 CONFIG_DEBUG_LOCKING_API_SELFTESTS=y
-CONFIG_DEBUG_WRITECOUNT=y
 CONFIG_DEBUG_LIST=y
 CONFIG_DEBUG_SG=y
 CONFIG_DEBUG_NOTIFIERS=y

arch/sh/configs/rsk7203_defconfig

@@ -128,7 +128,6 @@ CONFIG_DEBUG_MUTEXES=y
 CONFIG_DEBUG_SPINLOCK_SLEEP=y
 CONFIG_DEBUG_INFO=y
 CONFIG_DEBUG_VM=y
-CONFIG_DEBUG_WRITECOUNT=y
 CONFIG_DEBUG_LIST=y
 CONFIG_DEBUG_SG=y
 CONFIG_FRAME_POINTER=y

arch/xtensa/configs/iss_defconfig

@@ -627,7 +627,6 @@ CONFIG_SCHED_DEBUG=y
 # CONFIG_DEBUG_KOBJECT is not set
 # CONFIG_DEBUG_INFO is not set
 # CONFIG_DEBUG_VM is not set
-# CONFIG_DEBUG_WRITECOUNT is not set
 # CONFIG_DEBUG_MEMORY_INIT is not set
 # CONFIG_DEBUG_LIST is not set
 # CONFIG_DEBUG_SG is not set

arch/xtensa/configs/s6105_defconfig

@@ -569,7 +569,6 @@ CONFIG_DEBUG_SPINLOCK_SLEEP=y
 # CONFIG_DEBUG_INFO is not set
 # CONFIG_DEBUG_VM is not set
 CONFIG_DEBUG_NOMMU_REGIONS=y
-# CONFIG_DEBUG_WRITECOUNT is not set
 # CONFIG_DEBUG_MEMORY_INIT is not set
 # CONFIG_DEBUG_LIST is not set
 # CONFIG_DEBUG_SG is not set

fs/file_table.c

@@ -52,7 +52,6 @@ static void file_free_rcu(struct rcu_head *head)
 static inline void file_free(struct file *f)
 {
 	percpu_counter_dec(&nr_files);
-	file_check_state(f);
 	call_rcu(&f->f_u.fu_rcuhead, file_free_rcu);
 }
 
@@ -186,7 +185,6 @@ struct file *alloc_file(struct path *path, fmode_t mode,
 	 * that we can do debugging checks at __fput()
 	 */
 	if ((mode & FMODE_WRITE) && !special_file(path->dentry->d_inode->i_mode)) {
-		file_take_write(file);
 		WARN_ON(mnt_clone_write(path->mnt));
 	}
 	if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
@@ -213,10 +211,7 @@ static void drop_file_write_access(struct file *file)
 		return;
 
 	put_write_access(inode);
-	if (file_check_writeable(file) != 0)
-		return;
 	__mnt_drop_write(mnt);
-	file_release_write(file);
 }
 
 /* the real guts of fput() - releasing the last reference to file

fs/open.c

@@ -683,7 +683,6 @@ static int do_dentry_open(struct file *f,
 		error = __get_file_write_access(inode, f->f_path.mnt);
 		if (error)
 			goto cleanup_file;
-		file_take_write(f);
 	}
 
 	f->f_mapping = inode->i_mapping;
@@ -731,14 +730,7 @@ cleanup_all:
 	fops_put(f->f_op);
 	if (f->f_mode & FMODE_WRITE) {
 		if (!special_file(inode->i_mode)) {
-			/*
-			 * We don't consider this a real
-			 * mnt_want/drop_write() pair
-			 * because it all happenend right
-			 * here, so just reset the state.
-			 */
 			put_write_access(inode);
-			file_reset_write(f);
 			__mnt_drop_write(f->f_path.mnt);
 		}
 	}

include/linux/fs.h

@@ -769,9 +769,6 @@ static inline int ra_has_index(struct file_ra_state *ra, pgoff_t index)
 		index <  ra->start + ra->size);
 }
 
-#define FILE_MNT_WRITE_TAKEN	1
-#define FILE_MNT_WRITE_RELEASED	2
-
 struct file {
 	union {
 		struct llist_node	fu_llist;
@@ -809,9 +806,6 @@ struct file {
 	struct list_head	f_tfile_llink;
 #endif /* #ifdef CONFIG_EPOLL */
 	struct address_space	*f_mapping;
-#ifdef CONFIG_DEBUG_WRITECOUNT
-	unsigned long f_mnt_write_state;
-#endif
 } __attribute__((aligned(4)));	/* lest something weird decides that 2 is OK */
 
 struct file_handle {
@@ -829,49 +823,6 @@ static inline struct file *get_file(struct file *f)
 #define fput_atomic(x)	atomic_long_add_unless(&(x)->f_count, -1, 1)
 #define file_count(x)	atomic_long_read(&(x)->f_count)
 
-#ifdef CONFIG_DEBUG_WRITECOUNT
-static inline void file_take_write(struct file *f)
-{
-	WARN_ON(f->f_mnt_write_state != 0);
-	f->f_mnt_write_state = FILE_MNT_WRITE_TAKEN;
-}
-static inline void file_release_write(struct file *f)
-{
-	f->f_mnt_write_state |= FILE_MNT_WRITE_RELEASED;
-}
-static inline void file_reset_write(struct file *f)
-{
-	f->f_mnt_write_state = 0;
-}
-static inline void file_check_state(struct file *f)
-{
-	/*
-	 * At this point, either both or neither of these bits
-	 * should be set.
-	 */
-	WARN_ON(f->f_mnt_write_state == FILE_MNT_WRITE_TAKEN);
-	WARN_ON(f->f_mnt_write_state == FILE_MNT_WRITE_RELEASED);
-}
-static inline int file_check_writeable(struct file *f)
-{
-	if (f->f_mnt_write_state == FILE_MNT_WRITE_TAKEN)
-		return 0;
-	printk(KERN_WARNING "writeable file with no "
-			    "mnt_want_write()\n");
-	WARN_ON(1);
-	return -EINVAL;
-}
-#else /* !CONFIG_DEBUG_WRITECOUNT */
-static inline void file_take_write(struct file *filp) {}
-static inline void file_release_write(struct file *filp) {}
-static inline void file_reset_write(struct file *filp) {}
-static inline void file_check_state(struct file *filp) {}
-static inline int file_check_writeable(struct file *filp)
-{
-	return 0;
-}
-#endif /* CONFIG_DEBUG_WRITECOUNT */
-
 #define	MAX_NON_LFS	((1UL<<31) - 1)
 
 /* Page cache limit. The filesystems should put that into their s_maxbytes 

lib/Kconfig.debug

@@ -1030,16 +1030,6 @@ config DEBUG_BUGVERBOSE
 	  of the BUG call as well as the EIP and oops trace.  This aids
 	  debugging but costs about 70-100K of memory.
 
-config DEBUG_WRITECOUNT
-	bool "Debug filesystem writers count"
-	depends on DEBUG_KERNEL
-	help
-	  Enable this to catch wrong use of the writers count in struct
-	  vfsmount.  This will increase the size of each file struct by
-	  32 bits.
-
-	  If unsure, say N.
-
 config DEBUG_LIST
 	bool "Debug linked list manipulation"
 	depends on DEBUG_KERNEL