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Date: Fri, 11 Apr 2008 17:31:55 -0600
From: Andreas Dilger <adilger@....com>
To: Eric Sandeen <sandeen@...hat.com>
Cc: ext4 development <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH 2/3] reinstate ext4_ext_walk_space()
On Mar 26, 2008 10:42 -0500, Eric Sandeen wrote:
> the ext4 fiemap call needs this helper function.
>
> I need to dig for the original author to see what signed-off-by
> lines should be here.
This was originally written by Alex and was in the extents patches
but later removed.
> Index: linux-2.6.25-rc1/fs/ext4/extents.c
> ===================================================================
> --- linux-2.6.25-rc1.orig/fs/ext4/extents.c
> +++ linux-2.6.25-rc1/fs/ext4/extents.c
> @@ -1588,6 +1588,112 @@ 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, 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)
> Index: linux-2.6.25-rc1/include/linux/ext4_fs_extents.h
> ===================================================================
> --- linux-2.6.25-rc1.orig/include/linux/ext4_fs_extents.h
> +++ linux-2.6.25-rc1/include/linux/ext4_fs_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 *,
> + void *);
> +
> +#define EXT_CONTINUE 0
> +#define EXT_BREAK 1
> +#define EXT_REPEAT 2
>
> #define EXT_MAX_BLOCK 0xffffffff
>
> @@ -221,6 +234,7 @@ extern int ext4_ext_try_to_merge(struct
> 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 *,
>
> --
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Cheers, Andreas
--
Andreas Dilger
Sr. Staff Engineer, Lustre Group
Sun Microsystems of Canada, Inc.
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