* @inode: owner
* @ind: descriptor of indirect block.
*
- * This function returns the prefered place for block allocation.
+ * This function returns the preferred place for block allocation.
* It is used when heuristic for sequential allocation fails.
* Rules are:
* + if there is a block to the left of our position - allocate near it.
}
/**
- * ext4_find_goal - find a prefered place for allocation.
+ * ext4_find_goal - find a preferred place for allocation.
* @inode: owner
* @block: block we want
* @partial: pointer to the last triple within a chain
*
- * Normally this function find the prefered place for block allocation,
+ * Normally this function find the preferred place for block allocation,
* returns it.
*/
static ext4_fsblk_t ext4_find_goal(struct inode *inode, ext4_lblk_t block,
*/
#define DIO_CREDITS 25
+
+/*
+ *
+ *
+ * ext4_ext4 get_block() wrapper function
+ * It will do a look up first, and returns if the blocks already mapped.
+ * Otherwise it takes the write lock of the i_data_sem and allocate blocks
+ * and store the allocated blocks in the result buffer head and mark it
+ * mapped.
+ *
+ * If file type is extents based, it will call ext4_ext_get_blocks(),
+ * Otherwise, call with ext4_get_blocks_handle() to handle indirect mapping
+ * based files
+ *
+ * On success, it returns the number of blocks being mapped or allocate.
+ * if create==0 and the blocks are pre-allocated and uninitialized block,
+ * the result buffer head is unmapped. If the create ==1, it will make sure
+ * the buffer head is mapped.
+ *
+ * It returns 0 if plain look up failed (blocks have not been allocated), in
+ * that casem, buffer head is unmapped
+ *
+ * It returns the error in case of allocation failure.
+ */
int ext4_get_blocks_wrap(handle_t *handle, struct inode *inode, sector_t block,
unsigned long max_blocks, struct buffer_head *bh,
int create, int extend_disksize)
{
int retval;
+
+ clear_buffer_mapped(bh);
+
/*
* Try to see if we can get the block without requesting
* for new file system block.
inode, block, max_blocks, bh, 0, 0);
}
up_read((&EXT4_I(inode)->i_data_sem));
- if (!create || (retval > 0))
+
+ /* If it is only a block(s) look up */
+ if (!create)
+ return retval;
+
+ /*
+ * Returns if the blocks have already allocated
+ *
+ * Note that if blocks have been preallocated
+ * ext4_ext_get_block() returns th create = 0
+ * with buffer head unmapped.
+ */
+ if (retval > 0 && buffer_mapped(bh))
return retval;
/*
- * We need to allocate new blocks which will result
- * in i_data update
+ * New blocks allocate and/or writing to uninitialized extent
+ * will possibly result in updating i_data, so we take
+ * the write lock of i_data_sem, and call get_blocks()
+ * with create == 1 flag.
*/
down_write((&EXT4_I(inode)->i_data_sem));
/*