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Subject[patch 74/87] ext4: add EXT4_IOC_ALLOC_DA_BLKS ioctl
2.6.29-stable review patch.  If anyone has any objections, please let us know.

------------------

From: "Theodore Ts'o" <tytso@mit.edu>

(cherry picked from commit ccd2506bd43113659aa904d5bea5d1300605e2a6)

Add an ioctl which forces all of the delay allocated blocks to be
allocated. This also provides a function ext4_alloc_da_blocks() which
will be used by the following commits to force files to be fully
allocated to preserve application-expected ext3 behaviour.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
---
fs/ext4/ext4.h | 3 +++
fs/ext4/inode.c | 42 ++++++++++++++++++++++++++++++++++++++++++
fs/ext4/ioctl.c | 14 ++++++++++++++
3 files changed, 59 insertions(+)

--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -326,7 +326,9 @@ struct ext4_new_group_data {
#define EXT4_IOC_GROUP_EXTEND _IOW('f', 7, unsigned long)
#define EXT4_IOC_GROUP_ADD _IOW('f', 8, struct ext4_new_group_input)
#define EXT4_IOC_MIGRATE _IO('f', 9)
+ /* note ioctl 10 reserved for an early version of the FIEMAP ioctl */
/* note ioctl 11 reserved for filesystem-independent FIEMAP ioctl */
+#define EXT4_IOC_ALLOC_DA_BLKS _IO('f', 12)

/*
* ioctl commands in 32 bit emulation
@@ -1115,6 +1117,7 @@ extern int ext4_can_truncate(struct inod
extern void ext4_truncate(struct inode *);
extern void ext4_set_inode_flags(struct inode *);
extern void ext4_get_inode_flags(struct ext4_inode_info *);
+extern int ext4_alloc_da_blocks(struct inode *inode);
extern void ext4_set_aops(struct inode *inode);
extern int ext4_writepage_trans_blocks(struct inode *);
extern int ext4_meta_trans_blocks(struct inode *, int nrblocks, int idxblocks);
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -2816,6 +2816,48 @@ out:
return;
}

+/*
+ * Force all delayed allocation blocks to be allocated for a given inode.
+ */
+int ext4_alloc_da_blocks(struct inode *inode)
+{
+ if (!EXT4_I(inode)->i_reserved_data_blocks &&
+ !EXT4_I(inode)->i_reserved_meta_blocks)
+ return 0;
+
+ /*
+ * We do something simple for now. The filemap_flush() will
+ * also start triggering a write of the data blocks, which is
+ * not strictly speaking necessary (and for users of
+ * laptop_mode, not even desirable). However, to do otherwise
+ * would require replicating code paths in:
+ *
+ * ext4_da_writepages() ->
+ * write_cache_pages() ---> (via passed in callback function)
+ * __mpage_da_writepage() -->
+ * mpage_add_bh_to_extent()
+ * mpage_da_map_blocks()
+ *
+ * The problem is that write_cache_pages(), located in
+ * mm/page-writeback.c, marks pages clean in preparation for
+ * doing I/O, which is not desirable if we're not planning on
+ * doing I/O at all.
+ *
+ * We could call write_cache_pages(), and then redirty all of
+ * the pages by calling redirty_page_for_writeback() but that
+ * would be ugly in the extreme. So instead we would need to
+ * replicate parts of the code in the above functions,
+ * simplifying them becuase we wouldn't actually intend to
+ * write out the pages, but rather only collect contiguous
+ * logical block extents, call the multi-block allocator, and
+ * then update the buffer heads with the block allocations.
+ *
+ * For now, though, we'll cheat by calling filemap_flush(),
+ * which will map the blocks, and start the I/O, but not
+ * actually wait for the I/O to complete.
+ */
+ return filemap_flush(inode->i_mapping);
+}

/*
* bmap() is special. It gets used by applications such as lilo and by
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -262,6 +262,20 @@ setversion_out:
return err;
}

+ case EXT4_IOC_ALLOC_DA_BLKS:
+ {
+ int err;
+ if (!is_owner_or_cap(inode))
+ return -EACCES;
+
+ err = mnt_want_write(filp->f_path.mnt);
+ if (err)
+ return err;
+ err = ext4_alloc_da_blocks(inode);
+ mnt_drop_write(filp->f_path.mnt);
+ return err;
+ }
+
default:
return -ENOTTY;
}



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