[PATCH] BLOCK: Move functions out of buffer code [try #6]

Move some functions out of the buffering code that aren't strictly buffering
specific.  This is a precursor to being able to disable the block layer.

 (*) Moved some stuff out of fs/buffer.c:

     (*) The file sync and general sync stuff moved to fs/sync.c.

     (*) The superblock sync stuff moved to fs/super.c.

     (*) do_invalidatepage() moved to mm/truncate.c.

     (*) try_to_release_page() moved to mm/filemap.c.

 (*) Moved some related declarations between header files:

     (*) declarations for do_invalidatepage() and try_to_release_page() moved
     	 to linux/mm.h.

     (*) __set_page_dirty_buffers() moved to linux/buffer_head.h.

Signed-Off-By: David Howells <dhowells@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

9 files changed, 204 insertions, 177 deletions

diff --git a/fs/buffer.c b/fs/buffer.c
index 3b6d701073e7..16cfbcd254f1 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -159,31 +159,6 @@ int sync_blockdev(struct block_device *bdev)
 }
 EXPORT_SYMBOL(sync_blockdev);
 
-static void __fsync_super(struct super_block *sb)
-{
-        sync_inodes_sb(sb, 0);
-        DQUOT_SYNC(sb);
-        lock_super(sb);
-        if (sb->s_dirt && sb->s_op->write_super)
-                sb->s_op->write_super(sb);
-        unlock_super(sb);
-        if (sb->s_op->sync_fs)
-                sb->s_op->sync_fs(sb, 1);
-        sync_blockdev(sb->s_bdev);
-        sync_inodes_sb(sb, 1);
-}
-
-/*
- * Write out and wait upon all dirty data associated with this
- * superblock.  Filesystem data as well as the underlying block
- * device.  Takes the superblock lock.
- */
-int fsync_super(struct super_block *sb)
-{
-        __fsync_super(sb);
-        return sync_blockdev(sb->s_bdev);
-}
-
 /*
  * Write out and wait upon all dirty data associated with this
  * device.   Filesystem data as well as the underlying block
@@ -260,118 +235,6 @@ void thaw_bdev(struct block_device *bdev, struct super_block *sb)
 EXPORT_SYMBOL(thaw_bdev);
 
 /*
- * sync everything.  Start out by waking pdflush, because that writes back
- * all queues in parallel.
- */
-static void do_sync(unsigned long wait)
-{
-        wakeup_pdflush(0);
-        sync_inodes(0);         /* All mappings, inodes and their blockdevs */
-        DQUOT_SYNC(NULL);
-        sync_supers();          /* Write the superblocks */
-        sync_filesystems(0);    /* Start syncing the filesystems */
-        sync_filesystems(wait); /* Waitingly sync the filesystems */
-        sync_inodes(wait);      /* Mappings, inodes and blockdevs, again. */
-        if (!wait)
-                printk("Emergency Sync complete\n");
-        if (unlikely(laptop_mode))
-                laptop_sync_completion();
-}
-
-asmlinkage long sys_sync(void)
-{
-        do_sync(1);
-        return 0;
-}
-
-void emergency_sync(void)
-{
-        pdflush_operation(do_sync, 0);
-}
-
-/*
- * Generic function to fsync a file.
- *
- * filp may be NULL if called via the msync of a vma.
- */
- 
-int file_fsync(struct file *filp, struct dentry *dentry, int datasync)
-{
-        struct inode * inode = dentry->d_inode;
-        struct super_block * sb;
-        int ret, err;
-
-        /* sync the inode to buffers */
-        ret = write_inode_now(inode, 0);
-
-        /* sync the superblock to buffers */
-        sb = inode->i_sb;
-        lock_super(sb);
-        if (sb->s_op->write_super)
-                sb->s_op->write_super(sb);
-        unlock_super(sb);
-
-        /* .. finally sync the buffers to disk */
-        err = sync_blockdev(sb->s_bdev);
-        if (!ret)
-                ret = err;
-        return ret;
-}
-
-long do_fsync(struct file *file, int datasync)
-{
-        int ret;
-        int err;
-        struct address_space *mapping = file->f_mapping;
-
-        if (!file->f_op || !file->f_op->fsync) {
-                /* Why?  We can still call filemap_fdatawrite */
-                ret = -EINVAL;
-                goto out;
-        }
-
-        ret = filemap_fdatawrite(mapping);
-
-        /*
-         * We need to protect against concurrent writers, which could cause
-         * livelocks in fsync_buffers_list().
-         */
-        mutex_lock(&mapping->host->i_mutex);
-        err = file->f_op->fsync(file, file->f_dentry, datasync);
-        if (!ret)
-                ret = err;
-        mutex_unlock(&mapping->host->i_mutex);
-        err = filemap_fdatawait(mapping);
-        if (!ret)
-                ret = err;
-out:
-        return ret;
-}
-
-static long __do_fsync(unsigned int fd, int datasync)
-{
-        struct file *file;
-        int ret = -EBADF;
-
-        file = fget(fd);
-        if (file) {
-                ret = do_fsync(file, datasync);
-                fput(file);
-        }
-        return ret;
-}
-
-asmlinkage long sys_fsync(unsigned int fd)
-{
-        return __do_fsync(fd, 0);
-}
-
-asmlinkage long sys_fdatasync(unsigned int fd)
-{
-        return __do_fsync(fd, 1);
-}
-
-/*
  * Various filesystems appear to want __find_get_block to be non-blocking.
  * But it's the page lock which protects the buffers.  To get around this,
  * we get exclusion from try_to_free_buffers with the blockdev mapping's
@@ -1551,35 +1414,6 @@ static void discard_buffer(struct buffer_head * bh)
 }
 
 /**
- * try_to_release_page() - release old fs-specific metadata on a page
- *
- * @page: the page which the kernel is trying to free
- * @gfp_mask: memory allocation flags (and I/O mode)
- *
- * The address_space is to try to release any data against the page
- * (presumably at page->private).  If the release was successful, return `1'.
- * Otherwise return zero.
- *
- * The @gfp_mask argument specifies whether I/O may be performed to release
- * this page (__GFP_IO), and whether the call may block (__GFP_WAIT).
- *
- * NOTE: @gfp_mask may go away, and this function may become non-blocking.
- */
-int try_to_release_page(struct page *page, gfp_t gfp_mask)
-{
-        struct address_space * const mapping = page->mapping;
-
-        BUG_ON(!PageLocked(page));
-        if (PageWriteback(page))
-                return 0;
-        
-        if (mapping && mapping->a_ops->releasepage)
-                return mapping->a_ops->releasepage(page, gfp_mask);
-        return try_to_free_buffers(page);
-}
-EXPORT_SYMBOL(try_to_release_page);
-
-/**
  * block_invalidatepage - invalidate part of all of a buffer-backed page
  *
  * @page: the page which is affected
@@ -1630,14 +1464,6 @@ out:
 }
 EXPORT_SYMBOL(block_invalidatepage);
 
-void do_invalidatepage(struct page *page, unsigned long offset)
-{
-        void (*invalidatepage)(struct page *, unsigned long);
-        invalidatepage = page->mapping->a_ops->invalidatepage ? :
-                block_invalidatepage;
-        (*invalidatepage)(page, offset);
-}
-
 /*
  * We attach and possibly dirty the buffers atomically wrt
  * __set_page_dirty_buffers() via private_lock.  try_to_free_buffers
diff --git a/fs/super.c b/fs/super.c
index 6987824d0dce..15671cd048b1 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -220,6 +220,37 @@ static int grab_super(struct super_block *s) __releases(sb_lock)
         return 0;
 }
 
+/*
+ * Write out and wait upon all dirty data associated with this
+ * superblock.  Filesystem data as well as the underlying block
+ * device.  Takes the superblock lock.  Requires a second blkdev
+ * flush by the caller to complete the operation.
+ */
+void __fsync_super(struct super_block *sb)
+{
+        sync_inodes_sb(sb, 0);
+        DQUOT_SYNC(sb);
+        lock_super(sb);
+        if (sb->s_dirt && sb->s_op->write_super)
+                sb->s_op->write_super(sb);
+        unlock_super(sb);
+        if (sb->s_op->sync_fs)
+                sb->s_op->sync_fs(sb, 1);
+        sync_blockdev(sb->s_bdev);
+        sync_inodes_sb(sb, 1);
+}
+
+/*
+ * Write out and wait upon all dirty data associated with this
+ * superblock.  Filesystem data as well as the underlying block
+ * device.  Takes the superblock lock.
+ */
+int fsync_super(struct super_block *sb)
+{
+        __fsync_super(sb);
+        return sync_blockdev(sb->s_bdev);
+}
+
 /**
  *      generic_shutdown_super  -       common helper for ->kill_sb()
  *      @sb: superblock to kill
diff --git a/fs/sync.c b/fs/sync.c
index 955aef04da28..1de747b5ddb9 100644
--- a/fs/sync.c
+++ b/fs/sync.c
@@ -10,11 +10,124 @@
 #include <linux/syscalls.h>
 #include <linux/linkage.h>
 #include <linux/pagemap.h>
+#include <linux/quotaops.h>
+#include <linux/buffer_head.h>
 
 #define VALID_FLAGS (SYNC_FILE_RANGE_WAIT_BEFORE|SYNC_FILE_RANGE_WRITE| \
                         SYNC_FILE_RANGE_WAIT_AFTER)
 
 /*
+ * sync everything.  Start out by waking pdflush, because that writes back
+ * all queues in parallel.
+ */
+static void do_sync(unsigned long wait)
+{
+        wakeup_pdflush(0);
+        sync_inodes(0);         /* All mappings, inodes and their blockdevs */
+        DQUOT_SYNC(NULL);
+        sync_supers();          /* Write the superblocks */
+        sync_filesystems(0);    /* Start syncing the filesystems */
+        sync_filesystems(wait); /* Waitingly sync the filesystems */
+        sync_inodes(wait);      /* Mappings, inodes and blockdevs, again. */
+        if (!wait)
+                printk("Emergency Sync complete\n");
+        if (unlikely(laptop_mode))
+                laptop_sync_completion();
+}
+
+asmlinkage long sys_sync(void)
+{
+        do_sync(1);
+        return 0;
+}
+
+void emergency_sync(void)
+{
+        pdflush_operation(do_sync, 0);
+}
+
+/*
+ * Generic function to fsync a file.
+ *
+ * filp may be NULL if called via the msync of a vma.
+ */
+int file_fsync(struct file *filp, struct dentry *dentry, int datasync)
+{
+        struct inode * inode = dentry->d_inode;
+        struct super_block * sb;
+        int ret, err;
+
+        /* sync the inode to buffers */
+        ret = write_inode_now(inode, 0);
+
+        /* sync the superblock to buffers */
+        sb = inode->i_sb;
+        lock_super(sb);
+        if (sb->s_op->write_super)
+                sb->s_op->write_super(sb);
+        unlock_super(sb);
+
+        /* .. finally sync the buffers to disk */
+        err = sync_blockdev(sb->s_bdev);
+        if (!ret)
+                ret = err;
+        return ret;
+}
+
+long do_fsync(struct file *file, int datasync)
+{
+        int ret;
+        int err;
+        struct address_space *mapping = file->f_mapping;
+
+        if (!file->f_op || !file->f_op->fsync) {
+                /* Why?  We can still call filemap_fdatawrite */
+                ret = -EINVAL;
+                goto out;
+        }
+
+        ret = filemap_fdatawrite(mapping);
+
+        /*
+         * We need to protect against concurrent writers, which could cause
+         * livelocks in fsync_buffers_list().
+         */
+        mutex_lock(&mapping->host->i_mutex);
+        err = file->f_op->fsync(file, file->f_dentry, datasync);
+        if (!ret)
+                ret = err;
+        mutex_unlock(&mapping->host->i_mutex);
+        err = filemap_fdatawait(mapping);
+        if (!ret)
+                ret = err;
+out:
+        return ret;
+}
+
+static long __do_fsync(unsigned int fd, int datasync)
+{
+        struct file *file;
+        int ret = -EBADF;
+
+        file = fget(fd);
+        if (file) {
+                ret = do_fsync(file, datasync);
+                fput(file);
+        }
+        return ret;
+}
+
+asmlinkage long sys_fsync(unsigned int fd)
+{
+        return __do_fsync(fd, 0);
+}
+
+asmlinkage long sys_fdatasync(unsigned int fd)
+{
+        return __do_fsync(fd, 1);
+}
+
+/*
  * sys_sync_file_range() permits finely controlled syncing over a segment of
  * a file in the range offset .. (offset+nbytes-1) inclusive.  If nbytes is
  * zero then sys_sync_file_range() will operate from offset out to EOF.
diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index 737e407d0cd1..64b508e35d2a 100644
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -190,9 +190,7 @@ extern int buffer_heads_over_limit;
  * Generic address_space_operations implementations for buffer_head-backed
  * address_spaces.
  */
-int try_to_release_page(struct page * page, gfp_t gfp_mask);
 void block_invalidatepage(struct page *page, unsigned long offset);
-void do_invalidatepage(struct page *page, unsigned long offset);
 int block_write_full_page(struct page *page, get_block_t *get_block,
                                 struct writeback_control *wbc);
 int block_read_full_page(struct page*, get_block_t*);
@@ -302,4 +300,5 @@ static inline void lock_buffer(struct buffer_head *bh)
                 __lock_buffer(bh);
 }
 
+extern int __set_page_dirty_buffers(struct page *page);
 #endif /* _LINUX_BUFFER_HEAD_H */
diff --git a/include/linux/fs.h b/include/linux/fs.h
index d68c37af4dfb..1728142ec4b6 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1546,6 +1546,7 @@ extern int __filemap_fdatawrite_range(struct address_space *mapping,
 extern long do_fsync(struct file *file, int datasync);
 extern void sync_supers(void);
 extern void sync_filesystems(int wait);
+extern void __fsync_super(struct super_block *sb);
 extern void emergency_sync(void);
 extern void emergency_remount(void);
 extern int do_remount_sb(struct super_block *sb, int flags,
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 7b703b6d4358..4edf1934e5ca 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -743,7 +743,9 @@ int get_user_pages(struct task_struct *tsk, struct mm_struct *mm, unsigned long
                 int len, int write, int force, struct page **pages, struct vm_area_struct **vmas);
 void print_bad_pte(struct vm_area_struct *, pte_t, unsigned long);
 
-int __set_page_dirty_buffers(struct page *page);
+extern int try_to_release_page(struct page * page, gfp_t gfp_mask);
+extern void do_invalidatepage(struct page *page, unsigned long offset);
+
 int __set_page_dirty_nobuffers(struct page *page);
 int redirty_page_for_writepage(struct writeback_control *wbc,
                                 struct page *page);
diff --git a/mm/filemap.c b/mm/filemap.c
index 3277f3b23524..d6846de08887 100644
--- a/mm/filemap.c
+++ b/mm/filemap.c
@@ -2491,3 +2491,33 @@ generic_file_direct_IO(int rw, struct kiocb *iocb, const struct iovec *iov,
         }
         return retval;
 }
+
+/**
+ * try_to_release_page() - release old fs-specific metadata on a page
+ *
+ * @page: the page which the kernel is trying to free
+ * @gfp_mask: memory allocation flags (and I/O mode)
+ *
+ * The address_space is to try to release any data against the page
+ * (presumably at page->private).  If the release was successful, return `1'.
+ * Otherwise return zero.
+ *
+ * The @gfp_mask argument specifies whether I/O may be performed to release
+ * this page (__GFP_IO), and whether the call may block (__GFP_WAIT).
+ *
+ * NOTE: @gfp_mask may go away, and this function may become non-blocking.
+ */
+int try_to_release_page(struct page *page, gfp_t gfp_mask)
+{
+        struct address_space * const mapping = page->mapping;
+
+        BUG_ON(!PageLocked(page));
+        if (PageWriteback(page))
+                return 0;
+
+        if (mapping && mapping->a_ops->releasepage)
+                return mapping->a_ops->releasepage(page, gfp_mask);
+        return try_to_free_buffers(page);
+}
+
+EXPORT_SYMBOL(try_to_release_page);
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 488b7088557c..9fdcc7903956 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -30,6 +30,7 @@
 #include <linux/sysctl.h>
 #include <linux/cpu.h>
 #include <linux/syscalls.h>
+#include <linux/buffer_head.h>
 
 /*
  * The maximum number of pages to writeout in a single bdflush/kupdate
diff --git a/mm/truncate.c b/mm/truncate.c
index a654928323dc..cd3e34b816db 100644
--- a/mm/truncate.c
+++ b/mm/truncate.c
@@ -17,6 +17,30 @@
                                    do_invalidatepage */
 
 
+/**
+ * do_invalidatepage - invalidate part of all of a page
+ * @page: the page which is affected
+ * @offset: the index of the truncation point
+ *
+ * do_invalidatepage() is called when all or part of the page has become
+ * invalidated by a truncate operation.
+ *
+ * do_invalidatepage() does not have to release all buffers, but it must
+ * ensure that no dirty buffer is left outside @offset and that no I/O
+ * is underway against any of the blocks which are outside the truncation
+ * point.  Because the caller is about to free (and possibly reuse) those
+ * blocks on-disk.
+ */
+void do_invalidatepage(struct page *page, unsigned long offset)
+{
+        void (*invalidatepage)(struct page *, unsigned long);
+        invalidatepage = page->mapping->a_ops->invalidatepage;
+        if (!invalidatepage)
+                invalidatepage = block_invalidatepage;
+        if (invalidatepage)
+                (*invalidatepage)(page, offset);
+}
+
 static inline void truncate_partial_page(struct page *page, unsigned partial)
 {
         memclear_highpage_flush(page, partial, PAGE_CACHE_SIZE-partial);