[PATCH 4/4] Hook ext4 to the vfs fiemap interface.

Theodore Ts'o
2008-09-13T18:49:27Z

From: Eric Sandeen <sandeen@redhat.com>

ext4_ext_walk_space() was reinstated to be used for iterating over file
extents with a callback; it is used by the ext4 fiemap implementation.

Signed-off-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
---
fs/ext4/ext4.h | 2 +
fs/ext4/ext4_extents.h | 15 +++
fs/ext4/extents.c | 248 ++++++++++++++++++++++++++++++++++++++++++++++++
fs/ext4/file.c | 4 +
4 files changed, 269 insertions(+), 0 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 9fccf13..8ad9980 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -1127,6 +1127,8 @@ struct buffer_head *ext4_getblk(handle_t *, struct inode *,
ext4_lblk_t, int, int *);
struct buffer_head *ext4_bread(handle_t *, struct inode *,
ext4_lblk_t, int, int *);
+int ext4_get_block(struct inode *inode, sector_t iblock,
+ struct buffer_head *bh_result, int create);
int ext4_get_blocks_handle(handle_t *handle, struct inode *inode,
ext4_lblk_t iblock, unsigned long maxblocks,
struct buffer_head *bh_result,
diff --git a/fs/ext4/ext4_extents.h b/fs/ext4/ext4_extents.h
index 0f2c744..fbe34b4 100644
--- a/fs/ext4/ext4_extents.h
+++ b/fs/ext4/ext4_extents.h
@@ -124,6 +124,19 @@ struct ext4_ext_path {
#define EXT4_EXT_CACHE_GAP 1
#define EXT4_EXT_CACHE_EXTENT 2

+/*
+ * to be called by ext4_ext_walk_space()
+ * negative retcode - error
+ * positive retcode - signal for ext4_ext_walk_space(), see below
+ * callback must return valid extent (passed or newly created)
+ */
+typedef int (*ext_prepare_callback)(struct inode *, struct ext4_ext_path *,
+ struct ext4_ext_cache *,
+ struct ext4_extent *, void *);
+
+#define EXT_CONTINUE 0
+#define EXT_BREAK 1
+#define EXT_REPEAT 2

#define EXT_MAX_BLOCK 0xffffffff

@@ -224,6 +237,8 @@ extern int ext4_ext_try_to_merge(struct inode *inode,
struct ext4_extent *);
extern unsigned int ext4_ext_check_overlap(struct inode *, struct ext4_extent *, struct ext4_ext_path *);
extern int ext4_ext_insert_extent(handle_t *, struct inode *, struct ext4_ext_path *, struct ext4_extent *);
+extern int ext4_ext_walk_space(struct inode *, ext4_lblk_t, ext4_lblk_t,
+ ext_prepare_callback, void *);
extern struct ext4_ext_path *ext4_ext_find_extent(struct inode *, ext4_lblk_t,
struct ext4_ext_path *);
extern int ext4_ext_search_left(struct inode *, struct ext4_ext_path *,
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 6ff30ff..32c1aa9 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -40,6 +40,7 @@
#include <linux/slab.h>
#include <linux/falloc.h>
#include <asm/uaccess.h>
+#include <linux/fiemap.h>
#include "ext4_jbd2.h"
#include "ext4_extents.h"

@@ -1657,6 +1658,113 @@ cleanup:
return err;
}

+int ext4_ext_walk_space(struct inode *inode, ext4_lblk_t block,
+ ext4_lblk_t num, ext_prepare_callback func,
+ void *cbdata)
+{
+ struct ext4_ext_path *path = NULL;
+ struct ext4_ext_cache cbex;
+ struct ext4_extent *ex;
+ ext4_lblk_t next, start = 0, end = 0;
+ ext4_lblk_t last = block + num;
+ int depth, exists, err = 0;
+
+ BUG_ON(func == NULL);
+ BUG_ON(inode == NULL);
+
+ while (block < last && block != EXT_MAX_BLOCK) {
+ num = last - block;
+ /* find extent for this block */
+ path = ext4_ext_find_extent(inode, block, path);
+ if (IS_ERR(path)) {
+ err = PTR_ERR(path);
+ path = NULL;
+ break;
+ }
+
+ depth = ext_depth(inode);
+ BUG_ON(path[depth].p_hdr == NULL);
+ ex = path[depth].p_ext;
+ next = ext4_ext_next_allocated_block(path);
+
+ exists = 0;
+ if (!ex) {
+ /* there is no extent yet, so try to allocate
+ * all requested space */
+ start = block;
+ end = block + num;
+ } else if (le32_to_cpu(ex->ee_block) > block) {
+ /* need to allocate space before found extent */
+ start = block;
+ end = le32_to_cpu(ex->ee_block);
+ if (block + num < end)
+ end = block + num;
+ } else if (block >= le32_to_cpu(ex->ee_block)
+ + ext4_ext_get_actual_len(ex)) {
+ /* need to allocate space after found extent */
+ start = block;
+ end = block + num;
+ if (end >= next)
+ end = next;
+ } else if (block >= le32_to_cpu(ex->ee_block)) {
+ /*
+ * some part of requested space is covered
+ * by found extent
+ */
+ start = block;
+ end = le32_to_cpu(ex->ee_block)
+ + ext4_ext_get_actual_len(ex);
+ if (block + num < end)
+ end = block + num;
+ exists = 1;
+ } else {
+ BUG();
+ }
+ BUG_ON(end <= start);
+
+ if (!exists) {
+ cbex.ec_block = start;
+ cbex.ec_len = end - start;
+ cbex.ec_start = 0;
+ cbex.ec_type = EXT4_EXT_CACHE_GAP;
+ } else {
+ cbex.ec_block = le32_to_cpu(ex->ee_block);
+ cbex.ec_len = ext4_ext_get_actual_len(ex);
+ cbex.ec_start = ext_pblock(ex);
+ cbex.ec_type = EXT4_EXT_CACHE_EXTENT;
+ }
+
+ BUG_ON(cbex.ec_len == 0);
+ err = func(inode, path, &cbex, ex, cbdata);
+ ext4_ext_drop_refs(path);
+
+ if (err < 0)
+ break;
+
+ if (err == EXT_REPEAT)
+ continue;
+ else if (err == EXT_BREAK) {
+ err = 0;
+ break;
+ }
+
+ if (ext_depth(inode) != depth) {
+ /* depth was changed. we have to realloc path */
+ kfree(path);
+ path = NULL;
+ }
+
+ block = cbex.ec_block + cbex.ec_len;
+ }
+
+ if (path) {
+ ext4_ext_drop_refs(path);
+ kfree(path);
+ }
+
+ return err;
+}
+
static void
ext4_ext_put_in_cache(struct inode *inode, ext4_lblk_t block,
__u32 len, ext4_fsblk_t start, int type)
@@ -3006,3 +3114,143 @@ retry:
mutex_unlock(&inode->i_mutex);
return ret > 0 ? ret2 : ret;
}
+
+/*
+ * Callback function called for each extent to gather FIEMAP information.
+ */
+int ext4_ext_fiemap_cb(struct inode *inode, struct ext4_ext_path *path,
+ struct ext4_ext_cache *newex, struct ext4_extent *ex,
+ void *data)
+{
+ struct fiemap_extent_info *fieinfo = data;
+ unsigned long blksize_bits = inode->i_sb->s_blocksize_bits;
+ __u64 logical;
+ __u64 physical;
+ __u64 length;
+ __u32 flags = 0;
+ int error;
+
+ logical = (__u64)newex->ec_block << blksize_bits;
+
+ if (newex->ec_type == EXT4_EXT_CACHE_GAP) {
+ pgoff_t offset;
+ struct page *page;
+ struct buffer_head *bh = NULL;
+
+ offset = logical >> PAGE_SHIFT;
+ page = find_get_page(inode->i_mapping, offset);
+ if (!page || !page_has_buffers(page))
+ return EXT_CONTINUE;
+
+ bh = page_buffers(page);
+
+ if (!bh)
+ return EXT_CONTINUE;
+
+ if (buffer_delay(bh)) {
+ flags |= FIEMAP_EXTENT_DELALLOC;
+ page_cache_release(page);
+ } else {
+ page_cache_release(page);
+ return EXT_CONTINUE;
+ }
+ }
+
+ physical = (__u64)newex->ec_start << blksize_bits;
+ length = (__u64)newex->ec_len << blksize_bits;
+
+ if (ex && ext4_ext_is_uninitialized(ex))
+ flags |= FIEMAP_EXTENT_UNWRITTEN;
+
+ /*
+ * If this extent reaches EXT_MAX_BLOCK, it must be last.
+ *
+ * Or if ext4_ext_next_allocated_block is EXT_MAX_BLOCK,
+ * this also indicates no more allocated blocks.
+ *
+ * XXX this might miss a single-block extent at EXT_MAX_BLOCK
+ */
+ if (logical + length - 1 == EXT_MAX_BLOCK ||
+ ext4_ext_next_allocated_block(path) == EXT_MAX_BLOCK)
+ flags |= FIEMAP_EXTENT_LAST;
+
+ error = fiemap_fill_next_extent(fieinfo, logical, physical,
+ length, flags);
+ if (error < 0)
+ return error;
+ if (error == 1)
+ return EXT_BREAK;
+
+ return EXT_CONTINUE;
+}
+
+/* fiemap flags we can handle specified here */
+#define EXT4_FIEMAP_FLAGS (FIEMAP_FLAG_SYNC|FIEMAP_FLAG_XATTR)
+
+int ext4_xattr_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo)
+{
+ __u64 physical = 0;
+ __u64 length;
+ __u32 flags = FIEMAP_EXTENT_LAST;
+ int blockbits = inode->i_sb->s_blocksize_bits;
+ int error = 0;
+
+ /* in-inode? */
+ if (EXT4_I(inode)->i_state & EXT4_STATE_XATTR) {
+ struct ext4_iloc iloc;
+ int offset; /* offset of xattr in inode */
+
+ error = ext4_get_inode_loc(inode, &iloc);
+ if (error)
+ return error;
+ physical = iloc.bh->b_blocknr << blockbits;
+ offset = EXT4_GOOD_OLD_INODE_SIZE +
+ EXT4_I(inode)->i_extra_isize;
+ physical += offset;
+ length = EXT4_SB(inode->i_sb)->s_inode_size - offset;
+ flags |= FIEMAP_EXTENT_DATA_INLINE;
+ } else { /* external block */
+ physical = EXT4_I(inode)->i_file_acl << blockbits;
+ length = inode->i_sb->s_blocksize;
+ }
+
+ if (physical)
+ error = fiemap_fill_next_extent(fieinfo, 0, physical,
+ length, flags);
+ return (error < 0 ? error : 0);
+}
+
+int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
+ __u64 start, __u64 len)
+{
+ ext4_lblk_t start_blk;
+ ext4_lblk_t len_blks;
+ int error = 0;
+
+ /* fallback to generic here if not in extents fmt */
+ if (!(EXT4_I(inode)->i_flags & EXT4_EXTENTS_FL))
+ return generic_block_fiemap(inode, fieinfo, start, len,
+ ext4_get_block);
+
+ if (fiemap_check_flags(fieinfo, EXT4_FIEMAP_FLAGS))
+ return -EBADR;
+
+ if (fieinfo->fi_flags & FIEMAP_FLAG_XATTR) {
+ error = ext4_xattr_fiemap(inode, fieinfo);
+ } else {
+ start_blk = start >> inode->i_sb->s_blocksize_bits;
+ len_blks = len >> inode->i_sb->s_blocksize_bits;
+
+ /*
+ * Walk the extent tree gathering extent information.
+ * ext4_ext_fiemap_cb will push extents back to user.
+ */
+ down_write(&EXT4_I(inode)->i_data_sem);
+ error = ext4_ext_walk_space(inode, start_blk, len_blks,
+ ext4_ext_fiemap_cb, fieinfo);
+ up_write(&EXT4_I(inode)->i_data_sem);
+ }
+
+ return error;
+}
+
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 11b289f..8749d8e 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -140,6 +140,9 @@ static int ext4_file_mmap(struct file *file, struct vm_area_struct *vma)
return 0;
}

+extern int ext4_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
+ __u64 start, __u64 len);
+
const struct file_operations ext4_file_operations = {
.llseek = generic_file_llseek,
.read = do_sync_read,
@@ -170,5 +173,6 @@ const struct inode_operations ext4_file_inode_operations = {
#endif
.permission = ext4_permission,
.fallocate = ext4_fallocate,
+ .fiemap = ext4_fiemap,
};

--
1.5.6.1.205.ge2c7.dirty