fs/buffer.c: remove redundant initialization in alloc_page_buffers()

[can-eth-gw-linux.git] / fs / buffer.c

diff --git a/fs/buffer.c b/fs/buffer.c
index 28a74ff5324b86928c3dabd18618ddfd422a550a..c017a2dfb9097e73837230d244ffb14f73dd0e1c 100644 (file)
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -46,8 +46,7 @@ static int fsync_buffers_list(spinlock_t *lock, struct list_head *list);
 
 #define BH_ENTRY(list) list_entry((list), struct buffer_head, b_assoc_buffers)
 
-inline void
-init_buffer(struct buffer_head *bh, bh_end_io_t *handler, void *private)
+void init_buffer(struct buffer_head *bh, bh_end_io_t *handler, void *private)
 {
        bh->b_end_io = handler;
        bh->b_private = private;
@@ -555,7 +554,7 @@ void emergency_thaw_all(void)
  */
 int sync_mapping_buffers(struct address_space *mapping)
 {
-       struct address_space *buffer_mapping = mapping->assoc_mapping;
+       struct address_space *buffer_mapping = mapping->private_data;
 
        if (buffer_mapping == NULL || list_empty(&mapping->private_list))
                return 0;
@@ -588,10 +587,10 @@ void mark_buffer_dirty_inode(struct buffer_head *bh, struct inode *inode)
        struct address_space *buffer_mapping = bh->b_page->mapping;
 
        mark_buffer_dirty(bh);
-       if (!mapping->assoc_mapping) {
-               mapping->assoc_mapping = buffer_mapping;
+       if (!mapping->private_data) {
+               mapping->private_data = buffer_mapping;
        } else {
-               BUG_ON(mapping->assoc_mapping != buffer_mapping);
+               BUG_ON(mapping->private_data != buffer_mapping);
        }
        if (!bh->b_assoc_map) {
                spin_lock(&buffer_mapping->private_lock);
@@ -788,7 +787,7 @@ void invalidate_inode_buffers(struct inode *inode)
        if (inode_has_buffers(inode)) {
                struct address_space *mapping = &inode->i_data;
                struct list_head *list = &mapping->private_list;
-               struct address_space *buffer_mapping = mapping->assoc_mapping;
+               struct address_space *buffer_mapping = mapping->private_data;
 
                spin_lock(&buffer_mapping->private_lock);
                while (!list_empty(list))
@@ -811,7 +810,7 @@ int remove_inode_buffers(struct inode *inode)
        if (inode_has_buffers(inode)) {
                struct address_space *mapping = &inode->i_data;
                struct list_head *list = &mapping->private_list;
-               struct address_space *buffer_mapping = mapping->assoc_mapping;
+               struct address_space *buffer_mapping = mapping->private_data;
 
                spin_lock(&buffer_mapping->private_lock);
                while (!list_empty(list)) {
@@ -850,13 +849,10 @@ try_again:
                if (!bh)
                        goto no_grow;
 
-               bh->b_bdev = NULL;
                bh->b_this_page = head;
                bh->b_blocknr = -1;
                head = bh;
 
-               bh->b_state = 0;
-               atomic_set(&bh->b_count, 0);
                bh->b_size = size;
 
                /* Link the buffer to its page */
@@ -911,6 +907,18 @@ link_dev_buffers(struct page *page, struct buffer_head *head)
        attach_page_buffers(page, head);
 }
 
+static sector_t blkdev_max_block(struct block_device *bdev, unsigned int size)
+{
+       sector_t retval = ~((sector_t)0);
+       loff_t sz = i_size_read(bdev->bd_inode);
+
+       if (sz) {
+               unsigned int sizebits = blksize_bits(size);
+               retval = (sz >> sizebits);
+       }
+       return retval;
+}
+
 /*
  * Initialise the state of a blockdev page's buffers.
  */ 
@@ -921,7 +929,7 @@ init_page_buffers(struct page *page, struct block_device *bdev,
        struct buffer_head *head = page_buffers(page);
        struct buffer_head *bh = head;
        int uptodate = PageUptodate(page);
-       sector_t end_block = blkdev_max_block(I_BDEV(bdev->bd_inode));
+       sector_t end_block = blkdev_max_block(I_BDEV(bdev->bd_inode), size);
 
        do {
                if (!buffer_mapped(bh)) {
@@ -2881,6 +2889,55 @@ static void end_bio_bh_io_sync(struct bio *bio, int err)
        bio_put(bio);
 }
 
+/*
+ * This allows us to do IO even on the odd last sectors
+ * of a device, even if the bh block size is some multiple
+ * of the physical sector size.
+ *
+ * We'll just truncate the bio to the size of the device,
+ * and clear the end of the buffer head manually.
+ *
+ * Truly out-of-range accesses will turn into actual IO
+ * errors, this only handles the "we need to be able to
+ * do IO at the final sector" case.
+ */
+static void guard_bh_eod(int rw, struct bio *bio, struct buffer_head *bh)
+{
+       sector_t maxsector;
+       unsigned bytes;
+
+       maxsector = i_size_read(bio->bi_bdev->bd_inode) >> 9;
+       if (!maxsector)
+               return;
+
+       /*
+        * If the *whole* IO is past the end of the device,
+        * let it through, and the IO layer will turn it into
+        * an EIO.
+        */
+       if (unlikely(bio->bi_sector >= maxsector))
+               return;
+
+       maxsector -= bio->bi_sector;
+       bytes = bio->bi_size;
+       if (likely((bytes >> 9) <= maxsector))
+               return;
+
+       /* Uhhuh. We've got a bh that straddles the device size! */
+       bytes = maxsector << 9;
+
+       /* Truncate the bio.. */
+       bio->bi_size = bytes;
+       bio->bi_io_vec[0].bv_len = bytes;
+
+       /* ..and clear the end of the buffer for reads */
+       if ((rw & RW_MASK) == READ) {
+               void *kaddr = kmap_atomic(bh->b_page);
+               memset(kaddr + bh_offset(bh) + bytes, 0, bh->b_size - bytes);
+               kunmap_atomic(kaddr);
+       }
+}
+
 int submit_bh(int rw, struct buffer_head * bh)
 {
        struct bio *bio;
@@ -2917,6 +2974,9 @@ int submit_bh(int rw, struct buffer_head * bh)
        bio->bi_end_io = end_bio_bh_io_sync;
        bio->bi_private = bh;
 
+       /* Take care of bh's that straddle the end of the device */
+       guard_bh_eod(rw, bio, bh);
+
        bio_get(bio);
        submit_bio(rw, bio);