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-rw-r--r--fs/ext4/extents.c13
-rw-r--r--fs/ext4/inode.c47
2 files changed, 57 insertions, 3 deletions
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 8a59f7ba30e..bcf5d040e32 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -2287,9 +2287,22 @@ out:
}
/*
+ * Block allocation/map/preallocation routine for extents based files
+ *
+ *
* Need to be called with
* down_read(&EXT4_I(inode)->i_data_sem) if not allocating file system block
* (ie, create is zero). Otherwise down_write(&EXT4_I(inode)->i_data_sem)
+ *
+ * return > 0, number of of blocks already mapped/allocated
+ * if create == 0 and these are pre-allocated blocks
+ * buffer head is unmapped
+ * otherwise blocks are mapped
+ *
+ * return = 0, if plain look up failed (blocks have not been allocated)
+ * buffer head is unmapped
+ *
+ * return < 0, error case.
*/
int ext4_ext_get_blocks(handle_t *handle, struct inode *inode,
ext4_lblk_t iblock,
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 34f3eb615fd..945cbf6cb1f 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -908,11 +908,38 @@ out:
*/
#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.
@@ -926,12 +953,26 @@ int ext4_get_blocks_wrap(handle_t *handle, struct inode *inode, sector_t 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));
/*