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Btrfs: [PATCH] extent_map: provide generic bmap 

generic_bmap is completely trivial, while the extent to bh mapping in
btrfs is rather complex.  So provide a extent_bmap instead that takes
a get_extent callback and can be used by filesystem using the extent_map
code.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
This commit is contained in:
Christoph Hellwig 2007-09-10 20:02:30 -04:00 committed by David Woodhouse
parent 90f1c19a9f
commit d396c6f554
3 changed files with 23 additions and 21 deletions
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19
fs/btrfs/extent_map.c
View File

@ -1816,3 +1816,22 @@ int try_release_extent_mapping(struct extent_map_tree *tree, struct page *page)
}
EXPORT_SYMBOL(try_release_extent_mapping);
sector_t extent_bmap(struct address_space *mapping, sector_t iblock,
get_extent_t *get_extent)
{
struct inode *inode = mapping->host;
u64 start = iblock << inode->i_blkbits;
u64 end = start + (1 << inode->i_blkbits) - 1;
struct extent_map *em;
em = get_extent(inode, NULL, 0, start, end, 0);
if (!em || IS_ERR(em))
return 0;
// XXX(hch): block 0 is valid in some cases, e.g. XFS RT device
if (em->block_start == EXTENT_MAP_INLINE ||
em->block_start == 0)
return 0;
return (em->block_start + start - em->start) >> inode->i_blkbits;
}

2
fs/btrfs/extent_map.h
View File

@ -99,6 +99,8 @@ int extent_prepare_write(struct extent_map_tree *tree,
int extent_commit_write(struct extent_map_tree *tree,
struct inode *inode, struct page *page,
unsigned from, unsigned to);
sector_t extent_bmap(struct address_space *mapping, sector_t iblock,
get_extent_t *get_extent);
int set_range_dirty(struct extent_map_tree *tree, u64 start, u64 end);
int set_state_private(struct extent_map_tree *tree, u64 start, u64 private);
int get_state_private(struct extent_map_tree *tree, u64 start, u64 *private);

23
fs/btrfs/inode.c
View File

@ -1567,28 +1567,9 @@ out:
return em;
}
static int btrfs_get_block_bmap(struct inode *inode, sector_t iblock,
struct buffer_head *result, int create)
static sector_t btrfs_bmap(struct address_space *mapping, sector_t iblock)
{
struct btrfs_root *root = BTRFS_I(inode)->root;
u64 start = iblock << inode->i_blkbits;
u64 end = start + root->blocksize -1;
struct extent_map *em;
em = btrfs_get_extent(inode, NULL, 0, start, end, 0);
if (em && !IS_ERR(em) && em->block_start != EXTENT_MAP_INLINE &&
em->block_start != 0) {
u64 offset;
offset = start - em->start;
start = (em->block_start + offset) >> inode->i_blkbits;
btrfs_map_bh_to_logical(root, result, start);
}
return 0;
}
static sector_t btrfs_bmap(struct address_space *as, sector_t block)
{
return generic_block_bmap(as, block, btrfs_get_block_bmap);
return extent_bmap(mapping, iblock, btrfs_get_extent);
}
static int btrfs_prepare_write(struct file *file, struct page *page,