diff options
| -rw-r--r-- | fs/ext4/extents.c | 30 |
1 files changed, 26 insertions, 4 deletions
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c index 0554c48cb1fd..d53e20f53103 100644 --- a/fs/ext4/extents.c +++ b/fs/ext4/extents.c @@ -117,11 +117,33 @@ static ext4_fsblk_t ext4_ext_find_goal(struct inode *inode, struct ext4_extent *ex; depth = path->p_depth; - /* try to predict block placement */ + /* + * Try to predict block placement assuming that we are + * filling in a file which will eventually be + * non-sparse --- i.e., in the case of libbfd writing + * an ELF object sections out-of-order but in a way + * the eventually results in a contiguous object or + * executable file, or some database extending a table + * space file. However, this is actually somewhat + * non-ideal if we are writing a sparse file such as + * qemu or KVM writing a raw image file that is going + * to stay fairly sparse, since it will end up + * fragmenting the file system's free space. Maybe we + * should have some hueristics or some way to allow + * userspace to pass a hint to file system, + * especiially if the latter case turns out to be + * common. + */ ex = path[depth].p_ext; - if (ex) - return (ext4_ext_pblock(ex) + - (block - le32_to_cpu(ex->ee_block))); + if (ex) { + ext4_fsblk_t ext_pblk = ext4_ext_pblock(ex); + ext4_lblk_t ext_block = le32_to_cpu(ex->ee_block); + + if (block > ext_block) + return ext_pblk + (block - ext_block); + else + return ext_pblk - (ext_block - block); + } /* it looks like index is empty; * try to find starting block from index itself */ |