ext4: Split uninitialized extents for direct I/O

When writing into an unitialized extent via direct I/O, and the direct
I/O doesn't exactly cover the unitialized extent, split the extent
into uninitialized and initialized extents before submitting the I/O.
This avoids needing to deal with an ENOSPC error in the end_io
callback that gets used for direct I/O.

When the IO is complete, the written extent will be marked as initialized.

Singed-Off-By: Mingming Cao <cmm@us.ibm.com> 
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 21 insertions, 1 deletions

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index a58438e18d0b..2b4293aac162 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -128,6 +128,15 @@ struct mpage_da_data {
         int retval;
 };
 
+typedef struct ext4_io_end {
+        struct inode            *inode;         /* file being written to */
+        unsigned int            flag;           /* sync IO or AIO */
+        int                     error;          /* I/O error code */
+        ext4_lblk_t             offset;         /* offset in the file */
+        size_t                  size;           /* size of the extent */
+        struct work_struct      work;           /* data work queue */
+} ext4_io_end_t;
+
 /*
  * Special inodes numbers
  */
@@ -347,7 +356,16 @@ struct ext4_new_group_data {
         /* Call ext4_da_update_reserve_space() after successfully 
            allocating the blocks */
 #define EXT4_GET_BLOCKS_UPDATE_RESERVE_SPACE    0x0008
-
+        /* caller is from the direct IO path, request to creation of an
+        unitialized extents if not allocated, split the uninitialized
+        extent if blocks has been preallocated already*/
+#define EXT4_GET_BLOCKS_DIO                     0x0010
+#define EXT4_GET_BLOCKS_CONVERT                 0x0020
+#define EXT4_GET_BLOCKS_DIO_CREATE_EXT          (EXT4_GET_BLOCKS_DIO|\
+                                         EXT4_GET_BLOCKS_CREATE_UNINIT_EXT)
+        /* Convert extent to initialized after direct IO complete */
+#define EXT4_GET_BLOCKS_DIO_CONVERT_EXT         (EXT4_GET_BLOCKS_CONVERT|\
+                                         EXT4_GET_BLOCKS_DIO_CREATE_EXT)
 
 /*
  * ioctl commands
@@ -1700,6 +1718,8 @@ extern void ext4_ext_init(struct super_block *);
 extern void ext4_ext_release(struct super_block *);
 extern long ext4_fallocate(struct inode *inode, int mode, loff_t offset,
                           loff_t len);
+extern int ext4_convert_unwritten_extents(struct inode *inode, loff_t offset,
+                          loff_t len);
 extern int ext4_get_blocks(handle_t *handle, struct inode *inode,
                            sector_t block, unsigned int max_blocks,
                            struct buffer_head *bh, int flags);