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Message-Id: <1210875464-25552-4-git-send-email-sandeen@redhat.com>
Date: Thu, 15 May 2008 13:17:44 -0500
From: Eric Sandeen <sandeen@...hat.com>
To: sandeen@...hat.com
Subject: [PATCH 3/3] libext2fs: add ext2fs_extent_set_bmap
Allows unmapping or remapping single mapped logical blocks,
and mapping currently unmapped blocks.
Also implements ext2fs_extent_fix_parents() to fix parent
index logical starts, if the first index of a node changes
its logical start block.
Currently this results in new single-block extents; I think
perhaps ext2fs_extent_insert should grow a flag to request
merging with a nearby extent?
Signed-off-by: Eric Sandeen <sandeen@...hat.com>
---
lib/ext2fs/extent.c | 263 ++++++++++++++++++++++++++++++++++++++++++++++
lib/ext2fs/extent_dbg.ct | 3 +
2 files changed, 266 insertions(+), 0 deletions(-)
diff --git a/lib/ext2fs/extent.c b/lib/ext2fs/extent.c
index 8a6eaa2..821c05f 100644
--- a/lib/ext2fs/extent.c
+++ b/lib/ext2fs/extent.c
@@ -637,6 +637,64 @@ errcode_t ext2fs_extent_goto(ext2_extent_handle_t handle,
return extent_goto(handle, 0, blk);
}
+/*
+ * Traverse back up to root fixing parents of current node as needed.
+ *
+ * If we changed start of first entry in a node, fix parent index start
+ * and so on.
+ *
+ * Safe to call for any position in node; if not at the first entry,
+ * will simply return.
+ */
+errcode_t ext2fs_extent_fix_parents(ext2_extent_handle_t handle)
+{
+ int retval = 0;
+ blk64_t start;
+ struct extent_path *path;
+ struct ext2fs_extent extent;
+
+ EXT2_CHECK_MAGIC(handle, EXT2_ET_MAGIC_EXTENT_HANDLE);
+
+ if (!(handle->fs->flags & EXT2_FLAG_RW))
+ return EXT2_ET_RO_FILSYS;
+
+ if (!handle->path)
+ return EXT2_ET_NO_CURRENT_NODE;
+
+ path = handle->path + handle->level;
+ if (!path->curr)
+ return EXT2_ET_NO_CURRENT_NODE;
+
+ retval = ext2fs_extent_get(handle, EXT2_EXTENT_CURRENT, &extent);
+ if (retval)
+ goto done;
+
+ /* modified node's start block */
+ start = extent.e_lblk;
+
+ /* traverse up until index not first, or startblk matches, or top */
+ while (handle->level > 0 &&
+ (path->left == path->entries - 1)) {
+ retval = ext2fs_extent_get(handle, EXT2_EXTENT_UP, &extent);
+ if (retval)
+ goto done;
+ if (extent.e_lblk == start)
+ break;
+ path = handle->path + handle->level;
+ extent.e_len += (extent.e_lblk - start);
+ extent.e_lblk = start;
+ retval = ext2fs_extent_replace(handle, 0, &extent);
+ if (retval)
+ goto done;
+ update_path(handle);
+ }
+
+ /* put handle back to where we started */
+ retval = ext2fs_extent_goto(handle, start);
+done:
+ return retval;
+}
+
errcode_t ext2fs_extent_replace(ext2_extent_handle_t handle,
int flags EXT2FS_ATTR((unused)),
struct ext2fs_extent *extent)
@@ -938,6 +996,175 @@ errout:
return retval;
}
+/*
+ * Sets the physical block for a logical file block in the extent tree.
+ *
+ * May: map unmapped, unmap mapped, or remap mapped blocks.
+ *
+ * Mapping an unmapped block adds a single-block extent.
+ *
+ * Unmapping first or last block modifies extent in-place
+ * - But may need to fix parent's starts too in first-block case
+ *
+ * Mapping any unmapped block requires adding a (single-block) extent
+ * and inserting into proper point in tree.
+ *
+ * Modifying (unmapping or remapping) a block in the middle
+ * of an extent requires splitting the extent.
+ * - Remapping case requires new single-block extent.
+ *
+ * Remapping first or last block adds an extent.
+ *
+ * We really need extent adding to be smart about merging.
+ */
+
+errcode_t ext2fs_extent_set_bmap(ext2_extent_handle_t handle,
+ blk64_t logical, blk64_t physical)
+{
+ int retval = 0;
+ int mapped = 1; /* logical is mapped? */
+ struct extent_path *path;
+ struct ext2fs_extent extent;
+ struct ext2fs_extent newextent;
+
+ EXT2_CHECK_MAGIC(handle, EXT2_ET_MAGIC_EXTENT_HANDLE);
+
+ if (!(handle->fs->flags & EXT2_FLAG_RW))
+ return EXT2_ET_RO_FILSYS;
+
+ /* go to the logical spot we want to (re/un)map */
+ retval = ext2fs_extent_goto(handle, logical);
+ if (retval) {
+ if (retval == EXT2_ET_EXTENT_NOT_FOUND) {
+ retval = 0;
+ mapped = 0;
+ if (!physical) {
+ dbg_printf("block already unmapped\n");
+ goto done;
+ }
+ } else
+ goto done;
+ }
+
+ if (!handle->path)
+ return EXT2_ET_NO_CURRENT_NODE;
+
+ path = handle->path + handle->level;
+ if (!path->curr)
+ return EXT2_ET_NO_CURRENT_NODE;
+
+ /*
+ * This may be the extent *before* the requested logical,
+ * if it's currently unmapped.
+ */
+ retval = ext2fs_extent_get(handle, EXT2_EXTENT_CURRENT, &extent);
+ if (retval)
+ goto done;
+
+ /* check if already pointing to the requested physical */
+ if (mapped && extent.e_pblk + (logical - extent.e_lblk) == physical) {
+ dbg_printf("physical block unchanged\n");
+ goto done;
+ }
+
+ /* if (re)mapping, set up new extent, we'll insert it later */
+ if (physical) {
+ newextent.e_len = 1;
+ newextent.e_pblk = physical;
+ newextent.e_lblk = logical;
+ newextent.e_flags = EXT2_EXTENT_FLAGS_LEAF;
+ }
+
+ if (!mapped) {
+ dbg_printf("mapping unmapped logical block\n");
+ retval = ext2fs_extent_insert(handle,
+ EXT2_EXTENT_INSERT_AFTER, &newextent);
+ if (retval)
+ goto done;
+ retval = ext2fs_extent_fix_parents(handle);
+ if (retval)
+ goto done;
+ } else if (logical == extent.e_lblk + extent.e_len - 1 &&
+ extent.e_len == 1) {
+ dbg_printf("(re/un)mapping only block in extent\n");
+ if (physical) {
+ extent.e_pblk = physical;
+ retval = ext2fs_extent_replace(handle, 0, &extent);
+ } else {
+ retval = ext2fs_extent_delete(handle, 0);
+ if (retval)
+ goto done;
+ retval = ext2fs_extent_fix_parents(handle);
+ }
+
+ if (retval)
+ goto done;
+ } else if (logical == extent.e_lblk + extent.e_len - 1) {
+ dbg_printf("(re/un)mapping last block in extent\n");
+ extent.e_len--;
+ retval = ext2fs_extent_replace(handle, 0, &extent);
+ if (retval)
+ goto done;
+ if (physical) {
+ retval = ext2fs_extent_insert(handle,
+ EXT2_EXTENT_INSERT_AFTER, &newextent);
+ if (retval)
+ goto done;
+ }
+ } else if (logical == extent.e_lblk) {
+ dbg_printf("(re/un)mapping first block in extent\n");
+ extent.e_pblk++;
+ extent.e_lblk++;
+ extent.e_len--;
+ retval = ext2fs_extent_replace(handle, 0, &extent);
+ if (retval)
+ goto done;
+ if (physical) {
+ /* insert new extent ahead of current */
+ retval = ext2fs_extent_insert(handle,
+ 0, &newextent);
+ if (retval)
+ goto done;
+ } else {
+ retval = ext2fs_extent_fix_parents(handle);
+ if (retval)
+ goto done;
+ }
+ } else {
+ __u32 orig_length;
+
+ dbg_printf("(re/un)mapping in middle of extent\n");
+ /* need to split this extent; later */
+
+ orig_length = extent.e_len;
+
+ /* shorten pre-split extent */
+ extent.e_len = (logical - extent.e_lblk);
+ retval = ext2fs_extent_replace(handle, 0, &extent);
+ if (retval)
+ goto done;
+ /* insert our new extent, if any */
+ if (physical) {
+ /* insert new extent after current */
+ retval = ext2fs_extent_insert(handle,
+ EXT2_EXTENT_INSERT_AFTER, &newextent);
+ if (retval)
+ goto done;
+ }
+ /* add post-split extent */
+ extent.e_pblk += extent.e_len + 1;
+ extent.e_lblk += extent.e_len + 1;
+ extent.e_len = orig_length - extent.e_len - 1;
+ retval = ext2fs_extent_insert(handle,
+ EXT2_EXTENT_INSERT_AFTER, &extent);
+ if (retval)
+ goto done;
+ }
+
+done:
+ return retval;
+}
+
errcode_t ext2fs_extent_delete(ext2_extent_handle_t handle,
int flags EXT2FS_ATTR((unused)))
{
@@ -1277,6 +1504,42 @@ void do_insert_node(int argc, char *argv[])
do_current_node(argc, argv);
}
+void do_set_bmap(int argc, char **argv)
+{
+ errcode_t retval;
+ blk_t logical;
+ blk_t physical;
+ char *cmd;
+ int err;
+
+ if (check_fs_read_write(argv[0]))
+ return;
+
+ cmd = argv[0];
+
+ if (argc != 3) {
+ fprintf(stderr, "usage: %s <lblk> <pblk>\n", cmd);
+ return;
+ }
+
+ logical = parse_ulong(argv[1], cmd,
+ "logical block", &err);
+ if (err)
+ return;
+
+ physical = parse_ulong(argv[2], cmd,
+ "physical block", &err);
+ if (err)
+ return;
+
+ retval = ext2fs_extent_set_bmap(current_handle, logical, (blk64_t) physical);
+ if (retval) {
+ com_err(cmd, retval, 0);
+ return;
+ }
+ do_current_node(argc, argv);
+}
+
void do_print_all(int argc, char **argv)
{
struct ext2fs_extent extent;
diff --git a/lib/ext2fs/extent_dbg.ct b/lib/ext2fs/extent_dbg.ct
index 788fdab..d0571f4 100644
--- a/lib/ext2fs/extent_dbg.ct
+++ b/lib/ext2fs/extent_dbg.ct
@@ -55,6 +55,9 @@ request do_insert_node, "Insert node",
request do_split_node, "Split node",
split_node, split;
+request do_set_bmap, "Set block mapping",
+ set_bmap;
+
request do_replace_node, "Insert node",
replace_node, replace;
--
1.5.4.1
--
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