[PATCH 35/49] ext4: Clean up ext4_get_blocks() so it does not depend on bh_result->b_state

Theodore Ts'o
2009-06-08T19:28:05Z

The ext4_get_blocks() function was depending on the value of
bh_result->b_state as an input parameter to decide whether or not
update the delalloc accounting statistics by calling
ext4_da_update_reserve_space(). We now use a separate flag,
EXT4_GET_BLOCKS_UPDATE_RESERVE_SPACE, to requests this update, so that
all callers of ext4_get_blocks() can clear map_bh.b_state before
calling ext4_get_blocks() without worrying about any consistency
issues.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
---
fs/ext4/ext4.h | 15 +++++++++----
fs/ext4/inode.c | 56 ++++++++++++++++++++++++++++++------------------------
2 files changed, 41 insertions(+), 30 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 17feb4a..d164f12 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -318,16 +318,21 @@ struct ext4_new_group_data {
*/
/* Allocate any needed blocks and/or convert an unitialized
extent to be an initialized ext4 */
-#define EXT4_GET_BLOCKS_CREATE 1
+#define EXT4_GET_BLOCKS_CREATE 0x0001
/* Request the creation of an unitialized extent */
-#define EXT4_GET_BLOCKS_UNINIT_EXT 2
+#define EXT4_GET_BLOCKS_UNINIT_EXT 0x0002
#define EXT4_GET_BLOCKS_CREATE_UNINIT_EXT (EXT4_GET_BLOCKS_UNINIT_EXT|\
EXT4_GET_BLOCKS_CREATE)
/* Update the ext4_inode_info i_disksize field */
-#define EXT4_GET_BLOCKS_EXTEND_DISKSIZE 4
+#define EXT4_GET_BLOCKS_EXTEND_DISKSIZE 0x0004
/* Caller is from the delayed allocation writeout path,
- so the filesystem blocks have already been accounted for */
-#define EXT4_GET_BLOCKS_DELALLOC_RESERVE 8
+ so set the magic i_delalloc_reserve_flag after taking the
+ inode allocation semaphore for */
+#define EXT4_GET_BLOCKS_DELALLOC_RESERVE 0x0008
+ /* Call ext4_da_update_reserve_space() after successfully
+ allocating the blocks */
+#define EXT4_GET_BLOCKS_UPDATE_RESERVE_SPACE 0x0010
+

/*
* ioctl commands
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index bfe50a2..d7b7480 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -1234,16 +1234,15 @@ int ext4_get_blocks(handle_t *handle, struct inode *inode, sector_t block,
}
}

- if (flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE) {
+ if (flags & EXT4_GET_BLOCKS_DELALLOC_RESERVE)
EXT4_I(inode)->i_delalloc_reserved_flag = 0;
- /*
- * Update reserved blocks/metadata blocks
- * after successful block allocation
- * which were deferred till now
- */
- if ((retval > 0) && buffer_delay(bh))
- ext4_da_update_reserve_space(inode, retval);
- }
+
+ /*
+ * Update reserved blocks/metadata blocks after successful
+ * block allocation which had been deferred till now.
+ */
+ if ((retval > 0) && (flags & EXT4_GET_BLOCKS_UPDATE_RESERVE_SPACE))
+ ext4_da_update_reserve_space(inode, retval);

up_write((&EXT4_I(inode)->i_data_sem));
return retval;
@@ -2015,7 +2014,7 @@ static void ext4_print_free_blocks(struct inode *inode)
*/
static int mpage_da_map_blocks(struct mpage_da_data *mpd)
{
- int err, blks;
+ int err, blks, get_blocks_flags;
struct buffer_head new;
sector_t next = mpd->b_blocknr;
unsigned max_blocks = mpd->b_size >> mpd->inode->i_blkbits;
@@ -2040,23 +2039,30 @@ static int mpage_da_map_blocks(struct mpage_da_data *mpd)
BUG_ON(!handle);

/*
- * We need to make sure the BH_Delay flag is passed down to
- * ext4_da_get_block_write(), since it calls ext4_get_blocks()
- * with the EXT4_GET_BLOCKS_DELALLOC_RESERVE flag. This flag
- * causes ext4_get_blocks() to call
- * ext4_da_update_reserve_space() if the passed buffer head
- * has the BH_Delay flag set. In the future, once we clean up
- * the interfaces to ext4_get_blocks(), we should pass in a
- * separate flag which requests that the delayed allocation
- * statistics should be updated, instead of depending on the
- * state information getting passed down via the map_bh's
- * state bitmasks plus the magic
- * EXT4_GET_BLOCKS_DELALLOC_RESERVE flag.
+ * Call ext4_get_blocks() to allocate any delayed allocation
+ * blocks, or to convert an uninitialized extent to be
+ * initialized (in the case where we have written into
+ * one or more preallocated blocks).
+ *
+ * We pass in the magic EXT4_GET_BLOCKS_DELALLOC_RESERVE to
+ * indicate that we are on the delayed allocation path. This
+ * affects functions in many different parts of the allocation
+ * call path. This flag exists primarily because we don't
+ * want to change *many* call functions, so ext4_get_blocks()
+ * will set the magic i_delalloc_reserved_flag once the
+ * inode's allocation semaphore is taken.
+ *
+ * If the blocks in questions were delalloc blocks, set
+ * EXT4_GET_BLOCKS_DELALLOC_RESERVE so the delalloc accounting
+ * variables are updated after the blocks have been allocated.
*/
- new.b_state = mpd->b_state & (1 << BH_Delay);
+ new.b_state = 0;
+ get_blocks_flags = (EXT4_GET_BLOCKS_CREATE |
+ EXT4_GET_BLOCKS_DELALLOC_RESERVE);
+ if (mpd->b_state & (1 << BH_Delay))
+ get_blocks_flags |= EXT4_GET_BLOCKS_UPDATE_RESERVE_SPACE;
blks = ext4_get_blocks(handle, mpd->inode, next, max_blocks,
- &new, EXT4_GET_BLOCKS_CREATE|
- EXT4_GET_BLOCKS_DELALLOC_RESERVE);
+ &new, get_blocks_flags);
if (blks < 0) {
err = blks;
/*
--
1.6.3.2.1.gb9f7d.dirty