2007-04-03 10:07:59

by Aneesh Kumar K.V

[permalink] [raw]
Subject: [RFC][take 2] e2fsprogs: Add ext4migrate

This is work in progress


Changes from from my previous patches are as follows:


a) support for files with holes
b) use the block iterator present in libext2fs
c) don't mark the indirect blocks as unused early. If we mark the
the blocks unused, they can be resued for extent index. If we later
fail to migrate, the indirect blocks content would be overwritten.

The below patches add ext4migrate utility that helps in migrating
a ext3 block mapped inode to ext4 extent mapped inode. I have split
the patches into two. The purpose of splitting the patches into two
is to make the review easeir. The contents of [PATCH 1/2] is derived out of kernel source.

ext4migrate command takes the below syntax
ext4migrate [--display | --migrate ] <image_name> <filename>

The --display option helps in displaying the block map details for an ext3 inode
and extent map details for an ext4 inode. The --migrate option convert a block mapped
ext3 inode to extent mapped ext4 inode.

This needs to be run on an unmounted file system (offline migration).

The extent insert code is derived out of the latest ext4 kernel source. I have tried
to keep the code as close as possible to the kernel sources. This makes sure that any
fixes for the tree building code in kernel should be easily applied to ext4migrate.
The ext3_ext naming convention instead of ext4_ext found in kernel is to
make sure we are in sync with rest of e2fsprogs source.

The inode modification is done only at the last stage. This is to make sure that if we
fail at any intermediate stage, we exit without touching the disk.

The inode update is done as below
a) Walk the extent index blocks and write them to the disk. If failed exit
b) Write the inode. if failed exit.
c) Write the updated block bitmap. if failed exit ( This could be a problem because
we have already updated the inode i_block filed to point to new blocks.). But such
inconsistancy between inode i_block and block bitmap can be fixed by fsck IIUC.


With the above understanding i am not having a backup temporary inode during migration,
because even if we fail during migration we can recover the file contents.

The patch applies on top of e2fsprogs found at

http://www.kernel.org/pub/linux/kernel/people/tytso/e2fsprogs-interim/e2fsprogs-1.39-tyt1/e2fsprogs-1.39-tyt1.tar.bz2

-aneesh


2007-04-03 10:08:13

by Aneesh Kumar K.V

[permalink] [raw]
Subject: [PATCH 1/2] Add extent related functions

From: Aneesh Kumar K.V <[email protected]>

The code is derived out of the latest ext4 kernel source. I
have tried to keep the code as close as possible to the kernel
sources. This makes sure that any fixes for the tree building
code in kernel should be easily applied to ext4migrate. The
ext3_ext naming convention instead of ext4_ext found in kernel is to
make sure we are in sync with rest of e2fsprogs source

Signed-off-by: Aneesh Kumar K.V <[email protected]>
---
ext4migrate/extents.c | 737 +++++++++++++++++++++++++++++++++++++++++++++++++
ext4migrate/extents.h | 10 +
2 files changed, 747 insertions(+), 0 deletions(-)
create mode 100644 ext4migrate/extents.c
create mode 100644 ext4migrate/extents.h

diff --git a/ext4migrate/extents.c b/ext4migrate/extents.c
new file mode 100644
index 0000000..727755f
--- /dev/null
+++ b/ext4migrate/extents.c
@@ -0,0 +1,737 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "migrate.h"
+#include "extents.h"
+
+struct ext4_ext_path {
+ ext4_fsblk_t p_block;
+ __u16 p_depth;
+ struct ext3_extent *p_ext;
+ struct ext3_extent_idx *p_idx;
+ struct ext3_extent_header *p_hdr;
+};
+
+/*
+ * ext_pblock:
+ * combine low and high parts of physical block number into ext4_fsblk_t
+ */
+ext4_fsblk_t ext_pblock(struct ext3_extent *ex)
+{
+ ext4_fsblk_t block;
+
+ block = ex->ee_start;
+ block |= ((ext4_fsblk_t) ex->ee_start_hi << 31) << 1;
+ return block;
+}
+
+/*
+ * idx_pblock:
+ * combine low and high parts of a leaf physical block number into ext4_fsblk_t
+ */
+ext4_fsblk_t idx_pblock(struct ext3_extent_idx *ix)
+{
+ ext4_fsblk_t block;
+
+ block = ix->ei_leaf;
+ block |= ((ext4_fsblk_t) ix->ei_leaf_hi << 31) << 1;
+ return block;
+}
+
+/*
+ * ext3_ext_store_pblock:
+ * stores a large physical block number into an extent struct,
+ * breaking it into parts
+ */
+void ext3_ext_store_pblock(struct ext3_extent *ex, ext4_fsblk_t pb)
+{
+ ex->ee_start = (unsigned long) (pb & 0xffffffff);
+ ex->ee_start_hi = (unsigned long) ((pb >> 31) >> 1) & 0xffff;
+}
+
+/*
+ * ext3_idx_store_pblock:
+ * stores a large physical block number into an index struct,
+ * breaking it into parts
+ */
+static void ext3_idx_store_pblock(struct ext3_extent_idx *ix, ext4_fsblk_t pb)
+{
+ ix->ei_leaf = (unsigned long) (pb & 0xffffffff);
+ ix->ei_leaf_hi = (unsigned long) ((pb >> 31) >> 1) & 0xffff;
+}
+
+
+static int __ext3_ext_space_block(ext2_filsys filesys)
+{
+ int size;
+
+ size = (filesys->blocksize - sizeof(struct ext3_extent_header))
+ / sizeof(struct ext3_extent);
+ return size;
+}
+static int ext3_ext_space_block()
+{
+ return __ext3_ext_space_block(current_fs);
+}
+
+static int __ext3_ext_space_block_idx(ext2_filsys filesys)
+{
+ int size;
+
+ size = (filesys->blocksize - sizeof(struct ext3_extent_header))
+ / sizeof(struct ext3_extent_idx);
+ return size;
+}
+static int ext3_ext_space_block_idx()
+{
+ return __ext3_ext_space_block_idx(current_fs);
+
+}
+
+int ext3_ext_space_root(void)
+{
+ int size;
+
+ size = EXT2_N_BLOCKS*sizeof(blk_t);
+ size -= sizeof(struct ext3_extent_header);
+ size /= sizeof(struct ext3_extent);
+ return size;
+}
+
+static int ext3_ext_space_root_idx(void)
+{
+ int size;
+
+ size = EXT2_N_BLOCKS*sizeof(blk_t);
+ size -= sizeof(struct ext3_extent_header);
+ size /= sizeof(struct ext3_extent_idx);
+ return size;
+}
+static void ext3_ext_binsearch_idx(struct ext4_ext_path *path, blk_t logical_blk)
+{
+ struct ext3_extent_header *eh = path->p_hdr;
+ struct ext3_extent_idx *r, *l, *m;
+
+ l = EXT_FIRST_INDEX(eh) + 1;
+ r = EXT_FIRST_INDEX(eh) + eh->eh_entries - 1;
+ while (l <= r) {
+ m = l + (r - l) / 2;
+ if (logical_blk < m->ei_block)
+ r = m - 1;
+ else
+ l = m + 1;
+ }
+ path->p_idx = l - 1;
+}
+
+static void ext3_ext_binsearch(struct ext4_ext_path *path, blk_t logical_blk)
+{
+ struct ext3_extent_header *eh = path->p_hdr;
+ struct ext3_extent *r, *l, *m;
+
+ if (eh->eh_entries == 0) {
+ /*
+ * this leaf is empty:
+ * we get such a leaf in split/add case
+ */
+ return;
+ }
+
+ l = EXT_FIRST_EXTENT(eh) + 1;
+ r = EXT_FIRST_EXTENT(eh) + eh->eh_entries - 1;
+
+ while (l <= r) {
+ m = l + (r - l) / 2;
+ if (logical_blk < m->ee_block)
+ r = m - 1;
+ else
+ l = m + 1;
+ }
+
+ path->p_ext = l - 1;
+}
+
+/*
+ * ext3_ext_insert_index:
+ * insert new index [@logical;@ptr] into the block at @curp;
+ * check where to insert: before @curp or after @curp
+ */
+static int ext3_ext_insert_index(struct ext4_ext_path *curp,
+ int logical, ext4_fsblk_t ptr)
+{
+ struct ext3_extent_idx *ix;
+ int len, err = 0;
+
+ len = EXT_MAX_INDEX(curp->p_hdr) - curp->p_idx;
+ if (logical > curp->p_idx->ei_block) {
+ /* insert after */
+ if (curp->p_idx != EXT_LAST_INDEX(curp->p_hdr)) {
+ len = (len - 1) * sizeof(struct ext3_extent_idx);
+ len = len < 0 ? 0 : len;
+ memmove(curp->p_idx + 2, curp->p_idx + 1, len);
+ }
+ ix = curp->p_idx + 1;
+ } else {
+ /* insert before */
+ len = len * sizeof(struct ext3_extent_idx);
+ len = len < 0 ? 0 : len;
+ memmove(curp->p_idx + 1, curp->p_idx, len);
+ ix = curp->p_idx;
+ }
+
+ ix->ei_block = logical;
+ ext3_idx_store_pblock(ix, ptr);
+ curp->p_hdr->eh_entries = curp->p_hdr->eh_entries+1;
+
+ return err;
+}
+/*
+ * ext3_ext_split:
+ * inserts new subtree into the path, using free index entry
+ * at depth @at:
+ * - allocates all needed blocks (new leaf and all intermediate index blocks)
+ * - makes decision where to split
+ * - moves remaining extents and index entries (right to the split point)
+ * into the newly allocated blocks
+ * - initializes subtree
+ */
+static int ext3_ext_split(struct ext3_extent_header *eh, struct ext4_ext_path *path,
+ struct ext3_extent *newext, int at)
+{
+ int depth = eh->eh_depth;
+ struct ext3_extent_header *neh;
+ struct ext3_extent_idx *fidx;
+ struct ext3_extent *ex;
+ struct blk_cache *blkc;
+ int i = at, k, m, a;
+ ext4_fsblk_t newblock, oldblock;
+ int border;
+ ext4_fsblk_t *ablocks = NULL; /* array of allocated blocks */
+ int err = 0;
+
+ /* make decision: where to split? */
+ /* FIXME: now decision is simplest: at current extent */
+
+ /* if current leaf will be split, then we should use
+ * border from split point */
+ if (path[depth].p_ext != EXT_MAX_EXTENT(path[depth].p_hdr)) {
+ border = path[depth].p_ext[1].ee_block;
+ } else {
+ border = newext->ee_block;
+ }
+
+ /*
+ * If error occurs, then we break processing
+ * and mark filesystem read-only. index won't
+ * be inserted and tree will be in consistent
+ * state. Next mount will repair buffers too.
+ */
+
+ /*
+ * Get array to track all allocated blocks.
+ * We need this to handle errors and free blocks
+ * upon them.
+ */
+ ablocks = malloc(sizeof(ext4_fsblk_t) * depth);
+ if (!ablocks)
+ return -1;
+
+ memset(ablocks, 0, sizeof(ext4_fsblk_t) * depth);
+
+ /* allocate all needed blocks */
+ for (a = 0; a < depth - at; a++) {
+ blkc = get_block(0);
+ if (!blkc) {
+ err = EXT2_ET_BLOCK_ALLOC_FAIL;
+ goto cleanup;
+ }
+ newblock = blkc->pblock;
+ if (newblock == 0)
+ goto cleanup;
+ ablocks[a] = newblock;
+ }
+
+ /* initialize new leaf */
+ newblock = ablocks[--a];
+
+ neh = (struct ext3_extent_header *)(unsigned long)newblock;
+ neh->eh_entries = 0;
+ neh->eh_max = ext3_ext_space_block();
+ neh->eh_magic = EXT4_EXT_MAGIC;
+ neh->eh_depth = 0;
+ ex = EXT_FIRST_EXTENT(neh);
+
+ /* move remainder of path[depth] to the new leaf */
+ /* start copy from next extent */
+ /* TODO: we could do it by single memmove */
+ m = 0;
+ path[depth].p_ext++;
+ while (path[depth].p_ext <=
+ EXT_MAX_EXTENT(path[depth].p_hdr)) {
+ /*memmove(ex++, path[depth].p_ext++,
+ sizeof(struct ext4_extent));
+ neh->eh_entries++;*/
+ path[depth].p_ext++;
+ m++;
+ }
+
+ /*
+ * move the part of the old extent to the new allocated one
+ */
+ if (m) {
+ memmove(ex, path[depth].p_ext-m, sizeof(struct ext3_extent)*m);
+ neh->eh_entries = neh->eh_entries+m;
+ }
+
+ /* correct old leaf */
+ if (m) {
+ path[depth].p_hdr->eh_entries = path[depth].p_hdr->eh_entries-m;
+
+ }
+
+ /* create intermediate indexes */
+ k = depth - at - 1;
+
+ /*create intermediate indices */
+ /* insert new index into current index block */
+ /* current depth stored in i var */
+ i = depth - 1;
+ while (k--) {
+ oldblock = newblock;
+ newblock = ablocks[--a];
+
+ neh = (struct ext3_extent_header *)(unsigned long)newblock;
+ neh->eh_entries = 1;
+ neh->eh_magic = EXT4_EXT_MAGIC;
+ neh->eh_max = ext3_ext_space_block_idx();
+ neh->eh_depth = depth - i;
+ fidx = EXT_FIRST_INDEX(neh);
+ fidx->ei_block = border;
+ ext3_idx_store_pblock(fidx, oldblock);
+
+ /* copy indexes */
+ m = 0;
+ path[i].p_idx++;
+
+ while (path[i].p_idx <= EXT_MAX_INDEX(path[i].p_hdr)) {
+ /*memmove(++fidx, path[i].p_idx++,
+ sizeof(struct ext4_extent_idx));
+ neh->eh_entries++;
+ BUG_ON(neh->eh_entries > neh->eh_max);*/
+ path[i].p_idx++;
+ m++;
+ }
+ if (m) {
+ memmove(++fidx, path[i].p_idx - m,
+ sizeof(struct ext3_extent_idx) * m);
+ neh->eh_entries = neh->eh_entries + m;
+ }
+
+
+ /* correct old index */
+ if (m) {
+ path[i].p_hdr->eh_entries = path[i].p_hdr->eh_entries-m;
+ }
+
+ i--;
+ }
+
+ /* insert new index */
+ err = ext3_ext_insert_index(path + at, border, newblock);
+
+cleanup:
+
+ free(ablocks);
+
+ return err;
+}
+
+/*
+ * ext3_ext_grow_indepth:
+ * implements tree growing procedure:
+ * - allocates new block
+ * - moves top-level data (index block or leaf) into the new block
+ * - initializes new top-level, creating index that points to the
+ * just created block
+ */
+static int ext3_ext_grow_indepth(struct ext3_extent_header *eh, struct ext4_ext_path *path)
+{
+ struct ext4_ext_path *curp = path;
+ struct ext3_extent_header *neh;
+ struct blk_cache *blkc;
+ ext4_fsblk_t newblock;
+ void *addr;
+
+ blkc = get_block(0);
+ if (!blkc) {
+ return EXT2_ET_BLOCK_ALLOC_FAIL;
+
+ }
+ addr = blkc->block_mem_addr;
+ newblock = blkc->pblock;
+
+ /* move top-level index/leaf into new block */
+ memmove(addr, curp->p_hdr, EXT2_N_BLOCKS*sizeof(blk_t));
+
+ /* set size of new block */
+ neh = (struct ext3_extent_header *)addr;
+ /* old root could have indexes or leaves
+ * so calculate e_max right way */
+ if (eh->eh_depth) {
+ neh->eh_max = ext3_ext_space_block_idx();
+ } else {
+ neh->eh_max = ext3_ext_space_block();
+ }
+
+ neh->eh_magic = EXT4_EXT_MAGIC;
+
+ /* create index in new top-level index: num,max,pointer */
+
+ curp->p_hdr->eh_magic = EXT4_EXT_MAGIC;
+ curp->p_hdr->eh_max = ext3_ext_space_root_idx();
+ curp->p_hdr->eh_entries = 1;
+ curp->p_idx = EXT_FIRST_INDEX(curp->p_hdr);
+ /* FIXME: it works, but actually path[0] can be index */
+ curp->p_idx->ei_block = EXT_FIRST_EXTENT(path[0].p_hdr)->ee_block;
+ ext3_idx_store_pblock(curp->p_idx, newblock);
+
+ neh = eh;
+ //fidx = EXT_FIRST_INDEX(neh);
+
+ neh->eh_depth = path->p_depth + 1;
+
+ return 0;
+}
+struct ext4_ext_path * ext3_ext_find_extent(struct ext3_extent_header *eh,
+ blk_t logical_blk, struct ext4_ext_path *path)
+{
+
+ struct blk_cache *blkc;
+ short int depth, i, ppos = 0;
+ int alloc = 0;
+
+ i = depth = eh->eh_depth;
+
+ if (!path) {
+ /*
+ * We may be called to rebuild the path while growing the
+ * depth of the tree
+ */
+ path = malloc(sizeof(struct ext4_ext_path)* (depth+2));
+ if (!path)
+ return NULL;
+
+ alloc = 1;
+ memset(path, 0, sizeof(struct ext4_ext_path)* (depth+2));
+ }
+
+
+ path[0].p_hdr = eh;
+
+ while (i) {
+
+ ext3_ext_binsearch_idx(path, logical_blk);
+
+ path[ppos].p_block = idx_pblock(path[ppos].p_idx);
+ path[ppos].p_depth = i;
+ path[ppos].p_ext = NULL;
+
+ blkc = get_block(path[ppos].p_block);
+
+ if (!blkc) {
+ if (alloc)
+ free(path);
+ return NULL;
+ }
+
+ eh = blkc->block_mem_addr;
+ if (!eh) {
+ if (alloc)
+ free(path);
+ return NULL;
+ }
+ if (eh->eh_max == 0) {
+ if (alloc)
+ free(path);
+ return NULL;
+ }
+ ppos++;
+ path[ppos].p_hdr = eh;
+ i--;
+ }
+ path[ppos].p_depth = i;
+ path[ppos].p_hdr = eh;
+ path[ppos].p_ext = NULL;
+ path[ppos].p_idx = NULL;
+
+ ext3_ext_binsearch(path + ppos, logical_blk);
+
+ return path;
+}
+
+static int ext3_ext_create_new_leaf(struct ext3_extent_header *eh,
+ struct ext4_ext_path *path, struct ext3_extent *newext)
+{
+
+ struct ext4_ext_path *curp;
+ int depth, i, err = 0;
+
+repeat:
+ i = depth = eh->eh_depth;
+
+ /* walk up to the tree and look for free index entry */
+ curp = path + depth;
+ while (i > 0 && !EXT_HAS_FREE_INDEX(curp)) {
+ i--;
+ curp--;
+ }
+
+ if (EXT_HAS_FREE_INDEX(curp)) {
+
+ /* if we found index with free entry, then use that
+ * entry: create all needed subtree and add new leaf */
+ err = ext3_ext_split(eh, path, newext, i);
+ if (err)
+ goto err_out;
+
+ /* recalculate the path since grow inode would have changed it */
+ path = ext3_ext_find_extent(eh, newext->ee_block, path);
+ if (!path) {
+ err = EXT2_ET_BLOCK_ALLOC_FAIL;
+ goto err_out;
+ }
+
+ } else {
+
+ /* tree is full, time to grow in depth */
+ err = ext3_ext_grow_indepth(eh, path);
+ if (err)
+ goto err_out;
+
+ /* recalculate the path since grow inode would have changed it */
+ path = ext3_ext_find_extent(eh, newext->ee_block, path);
+ if (!path) {
+ err = EXT2_ET_BLOCK_ALLOC_FAIL;
+ goto err_out;
+ }
+
+
+ /*
+ * only first (depth 0 -> 1) produces free space;
+ * in all other cases we have to split the grown tree
+ */
+ depth = eh->eh_depth;
+ if (path[depth].p_hdr->eh_entries == path[depth].p_hdr->eh_max) {
+ /* now we need to split */
+ goto repeat;
+ }
+
+ }
+
+err_out:
+
+ return err;
+}
+
+static int ext3_can_extents_be_merged(struct ext3_extent *ex1, struct ext3_extent *ex2)
+{
+ if (ex1->ee_block + ex1->ee_len != ex2->ee_block)
+ return 0;
+
+
+ if (ext_pblock(ex1) + ex1->ee_len == ext_pblock(ex2))
+ return 1;
+ return 0;
+}
+
+
+/*
+ * ext3_ext_next_leaf_block:
+ * returns first allocated block from next leaf or EXT_MAX_BLOCK
+ */
+static unsigned ext3_ext_next_leaf_block(struct ext4_ext_path *path)
+{
+ int depth;
+
+ depth = path->p_depth;
+
+ /* zero-tree has no leaf blocks at all */
+ if (depth == 0)
+ return EXT_MAX_BLOCK;
+
+ /* go to index block */
+ depth--;
+
+ while (depth >= 0) {
+ if (path[depth].p_idx != EXT_LAST_INDEX(path[depth].p_hdr)) {
+ return path[depth].p_idx[1].ei_block;
+ }
+ depth--;
+ }
+
+ return EXT_MAX_BLOCK;
+}
+
+/*
+ * ext3_ext_correct_indexes:
+ * if leaf gets modified and modified extent is first in the leaf,
+ * then we have to correct all indexes above.
+ * TODO: do we need to correct tree in all cases?
+ */
+static void ext3_ext_correct_indexes(struct ext3_extent_header *eh, struct ext4_ext_path *path)
+{
+ int depth = eh->eh_depth;
+ struct ext3_extent *ex;
+ int border;
+ int k;
+
+
+ eh = path[depth].p_hdr;
+ ex = path[depth].p_ext;
+
+ if (depth == 0) {
+ /* there is no tree at all */
+ return;
+ }
+
+ if (ex != EXT_FIRST_EXTENT(eh)) {
+ /* we correct tree if first leaf got modified only */
+ return;
+ }
+
+ /*
+ * TODO: we need correction if border is smaller than current one
+ */
+ k = depth - 1;
+ border = path[depth].p_ext->ee_block;
+ path[k].p_idx->ei_block = border;
+
+ while (k--) {
+ /* change all left-side indexes */
+ if (path[k+1].p_idx != EXT_FIRST_INDEX(path[k+1].p_hdr))
+ break;
+ path[k].p_idx->ei_block = border;
+ }
+
+ return;
+}
+
+int ext3_ext_insert_extent(struct ext3_extent_header *eh,
+ struct ext4_ext_path *path, struct ext3_extent *newext)
+{
+
+ struct ext3_extent *ex, *fex;
+ struct ext3_extent *nearex; /* nearest extent */
+ struct ext4_ext_path *npath = NULL;
+ int depth, len, err = 0, next;
+ struct ext3_extent_header *save_eh = eh;
+
+ depth = eh->eh_depth;
+ ex = path[depth].p_ext;
+
+ /* try to insert block into found extent and return */
+ if (ex && ext3_can_extents_be_merged(ex, newext)) {
+ ex->ee_len = ex->ee_len + newext->ee_len;
+ eh = path[depth].p_hdr;
+ nearex = ex;
+ goto merge;
+ }
+
+repeat:
+ /* recalculate depth here */
+ depth=save_eh->eh_depth;
+
+ eh = path[depth].p_hdr;
+ if (eh->eh_entries < eh->eh_max)
+ goto has_space;
+
+ /* probably next leaf has space for us? */
+ fex = EXT_LAST_EXTENT(eh);
+ next = ext3_ext_next_leaf_block(path);
+
+ if (newext->ee_block > fex->ee_block && next != EXT_MAX_BLOCK) {
+
+ npath = ext3_ext_find_extent(save_eh, next, NULL);
+ if (!npath) {
+ return EXT2_ET_BLOCK_ALLOC_FAIL;
+ }
+
+ eh = npath[depth].p_hdr;
+ if (eh->eh_entries < eh->eh_max) {
+ path = npath;
+ goto repeat;
+ }
+ }
+
+ /*
+ * There is no free space in the found leaf.
+ * We're gonna add a new leaf in the tree.
+ */
+ err = ext3_ext_create_new_leaf(save_eh, path, newext);
+ if (err)
+ goto cleanup;
+
+ /* recalculate depth here */
+ depth=save_eh->eh_depth;
+ eh = path[depth].p_hdr;
+
+has_space:
+
+ nearex = path[depth].p_ext;
+
+ if (!nearex) {
+ /* there is no extent in this leaf, create first one */
+ path[depth].p_ext = EXT_FIRST_EXTENT(eh);
+
+ } else if (newext->ee_block > nearex->ee_block) {
+
+ if (nearex != EXT_LAST_EXTENT(eh)) {
+ len = EXT_MAX_EXTENT(eh) - nearex;
+ len = (len - 1) * sizeof(struct ext3_extent);
+ len = len < 0 ? 0 : len;
+ memmove(nearex + 2, nearex + 1, len);
+ }
+ path[depth].p_ext = nearex + 1;
+ } else {
+ len = (EXT_MAX_EXTENT(eh) - nearex) * sizeof(struct ext3_extent);
+ len = len < 0 ? 0 : len;
+ memmove(nearex + 1, nearex, len);
+ path[depth].p_ext = nearex;
+ }
+
+ eh->eh_entries = eh->eh_entries+1;
+ nearex = path[depth].p_ext;
+ nearex->ee_block = newext->ee_block;
+ nearex->ee_start = newext->ee_start;
+ nearex->ee_start_hi = newext->ee_start_hi;
+ nearex->ee_len = newext->ee_len;
+
+merge:
+ /* try to merge extents to the right */
+ while (nearex < EXT_LAST_EXTENT(eh)) {
+ if (!ext3_can_extents_be_merged(nearex, nearex + 1))
+ break;
+ /* merge with next extent! */
+ nearex->ee_len = nearex->ee_len + nearex[1].ee_len;
+
+ if (nearex + 1 < EXT_LAST_EXTENT(eh)) {
+ len = (EXT_LAST_EXTENT(eh) - nearex - 1)
+ * sizeof(struct ext3_extent);
+ memmove(nearex + 1, nearex + 2, len);
+ }
+ eh->eh_entries = eh->eh_entries-1;
+ }
+
+ /* try to merge extents to the left */
+
+ /* time to correct all indexes above */
+ ext3_ext_correct_indexes(save_eh, path);
+
+cleanup:
+ if (npath) {
+ free(npath);
+ }
+
+ return err;
+}
+
diff --git a/ext4migrate/extents.h b/ext4migrate/extents.h
new file mode 100644
index 0000000..38114dd
--- /dev/null
+++ b/ext4migrate/extents.h
@@ -0,0 +1,10 @@
+
+struct ext4_ext_path * ext3_ext_find_extent(struct ext3_extent_header *,
+ blk_t , struct ext4_ext_path *);
+struct blk_cache * get_block(ext4_fsblk_t);
+int ext3_ext_space_root(void);
+ext4_fsblk_t ext_pblock(struct ext3_extent *);
+ext4_fsblk_t idx_pblock(struct ext3_extent_idx *);
+void ext3_ext_store_pblock(struct ext3_extent *, ext4_fsblk_t );
+int ext3_ext_insert_extent(struct ext3_extent_header *,
+ struct ext4_ext_path *, struct ext3_extent *);
--
1.5.1.rc3.30.ga8f4-dirty

2007-04-03 10:08:47

by Aneesh Kumar K.V

[permalink] [raw]
Subject: [PATCH 2/2] e2fsprogs: Add ext4migrate

From: Aneesh Kumar K.V <[email protected]>

Add ext4migrate utility that helps in migrating a ext3 block mapped
inode to ext4 extent mapped inode.

ext4migrate command takes the below syntax
ext4migrate [--display | --migrate ] <image_name> <filename>

The --display option helps in displaying the block map details for an ext3 inode
and extent map details for an ext4 inode. The --migrate option convert a block mapped
ext3 inode to extent mapped ext4 inode.

This needs to be run on an unmounted file system (offline migration).

The inode modification is done only at the last stage. This is to make sure that if we
fail at any intermediate stage, we exit without touching the disk.

Signed-off-by: Aneesh Kumar K.V <[email protected]>
---
Makefile.in | 3 +-
configure.in | 21 ++-
ext4migrate/Makefile.in | 66 +++++++
ext4migrate/migrate.c | 491 +++++++++++++++++++++++++++++++++++++++++++++++
ext4migrate/migrate.h | 27 +++
5 files changed, 606 insertions(+), 2 deletions(-)
create mode 100644 ext4migrate/Makefile.in
create mode 100644 ext4migrate/migrate.c
create mode 100644 ext4migrate/migrate.h

diff --git a/Makefile.in b/Makefile.in
index 0d31caa..9d8d291 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -9,9 +9,10 @@ INSTALL = @[email protected]

@[email protected]_DIR= resize
@[email protected]_DIR= debugfs
[email protected][email protected]_DIR= ext4migrate

LIB_SUBDIRS=lib/et lib/ss lib/e2p lib/ext2fs lib/uuid lib/blkid intl
-PROG_SUBDIRS=e2fsck $(DEBUGFS_DIR) misc $(RESIZE_DIR) tests/progs po
+PROG_SUBDIRS=e2fsck $(DEBUGFS_DIR) misc $(RESIZE_DIR) tests/progs po $(EXT4MIGRATE_DIR)
SUBDIRS=util $(LIB_SUBDIRS) $(PROG_SUBDIRS) tests

SUBS= lib/ext2fs/ext2_types.h lib/blkid/blkid_types.h lib/uuid/uuid_types.h
diff --git a/configure.in b/configure.in
index 44b718d..5ae5e0b 100644
--- a/configure.in
+++ b/configure.in
@@ -436,6 +436,24 @@ echo "Building e2fsck statically by default"
)
AC_SUBST(E2FSCK_TYPE)
dnl
+dnl handle --enable-ext4migrate
+dnl
+AC_ARG_ENABLE([ext4migrate],
+[ --disable-ext4migrate disable support of ext4migrate program],
+if test "$enableval" = "no"
+then
+ echo "Disabling ext4migrate support"
+ EXT4MIGRATE_CMT="#"
+else
+ EXT4MIGRATE_CMT=
+ echo "Enabling ext4migrate support"
+fi
+,
+echo "Enabling ext4migrate support by default"
+EXT4MIGRATE_CMT=
+)
+AC_SUBST(EXT4MIGRATE_CMT)
+dnl
dnl See whether to install the `fsck' wrapper program (that calls e2fsck)
dnl
AC_ARG_ENABLE([fsck],
@@ -862,7 +880,8 @@ for i in MCONFIG Makefile e2fsprogs.spec \
lib/e2p/e2p.pc lib/blkid/blkid.pc lib/ext2fs/ext2fs.pc \
misc/Makefile ext2ed/Makefile e2fsck/Makefile \
debugfs/Makefile tests/Makefile tests/progs/Makefile \
- resize/Makefile doc/Makefile intl/Makefile po/Makefile.in ; do
+ resize/Makefile doc/Makefile intl/Makefile po/Makefile.in \
+ ext4migrate/Makefile ; do
if test -d `dirname ${srcdir}/$i` ; then
outlist="$outlist $i"
fi
diff --git a/ext4migrate/Makefile.in b/ext4migrate/Makefile.in
new file mode 100644
index 0000000..2596508
--- /dev/null
+++ b/ext4migrate/Makefile.in
@@ -0,0 +1,66 @@
+#
+# Standard e2fsprogs prologue....
+#
+
+srcdir = @[email protected]
+top_srcdir = @[email protected]
+VPATH = @[email protected]
+top_builddir = ..
+my_dir = util
+INSTALL = @[email protected]
[email protected]@
+
+SRCS = $(srcdir)/migrate.c
+
+LIBS= $(LIBEXT2FS) $(LIBCOM_ERR)
+DEPLIBS= $(LIBEXT2FS) $(LIBCOM_ERR)
+
+.c.o:
+ @echo " CC $<"
+ @$(CC) -c $(ALL_CFLAGS) $< -o [email protected]
+ @#cc -g -I../lib/ -Wunreachable-code -Wunused -Wunused-function
+ @#-Wunused-label -Wunused-parameter -Wunused-value -Wunused-variable -c migrate.c
+
+PROGS= ext4migrate
+
+all:: $(PROGS)
+
+ext4migrate: migrate.o extents.o $(DEPLIBS)
+ @echo " LD [email protected]"
+ @$(CC) $(ALL_LDFLAGS) -o ext4migrate migrate.o extents.o $(LIBS)
+
+installdirs:
+ @echo " MKINSTALLDIRS $(root_sbindir)"
+ @$(MKINSTALLDIRS) $(DESTDIR)$(root_sbindir)
+
+install: $(PROGS) installdirs
+ @for i in $(PROGS); do \
+ echo " INSTALL $(root_sbindir)/$$i"; \
+ $(INSTALL_PROGRAM) $$i $(DESTDIR)$(root_sbindir)/$$i; \
+ done
+
+install-strip: install
+ @for i in $(PROGS); do \
+ echo " STRIP $(root_sbindir)/$$i"; \
+ $(STRIP) $(DESTDIR)$(root_sbindir)/$$i; \
+ done
+
+uninstall:
+ for i in $(PROGS); do \
+ $(RM) -f $(DESTDIR)$(root_sbindir)/$$i; \
+ done
+clean:
+ $(RM) -f $(PROGS) \#* *.s *.o *.a *~ core
+
+mostlyclean: clean
+
+distclean: clean
+ $(RM) -f .depend Makefile $(srcdir)/TAGS $(srcdir)/Makefile.in.old
+
+# +++ Dependency line eater +++
+#
+# Makefile dependencies follow. This must be the last section in
+# the Makefile.in file
+#
+migrate.o: $(srcdir)/migrate.c
+extents.o: $(srcdir)/extents.c
diff --git a/ext4migrate/migrate.c b/ext4migrate/migrate.c
new file mode 100644
index 0000000..0d851cc
--- /dev/null
+++ b/ext4migrate/migrate.c
@@ -0,0 +1,491 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "migrate.h"
+#include "extents.h"
+
+static struct list_head blk_cache_head;
+static struct list_head blk_stat_head;
+static blk_t i_block[EXT2_N_BLOCKS];
+static int migrate = 0;
+ext2_filsys current_fs = NULL;
+
+static void blk_init(void)
+{
+ INIT_LIST_HEAD(&blk_cache_head);
+ INIT_LIST_HEAD(&blk_stat_head);
+}
+
+static void inode_i_block_init()
+{
+ struct ext3_extent_header *eh = (struct ext3_extent_header *)i_block;
+ eh->eh_magic = EXT4_EXT_MAGIC;
+ eh->eh_entries = 0;
+ eh->eh_depth = 0;
+ eh->eh_max = ext3_ext_space_root();
+}
+
+static void usage(char *prg_name)
+{
+ fprintf(stderr, "%s [--display | --migrate ] <image_name> <filename>\n", prg_name);
+ exit(1);
+}
+
+static int build_extent(blk_t start_blk, blk_t end_blk, e2_blkcnt_t start_pblk, e2_blkcnt_t end_pblk)
+{
+
+ int retval = 0;
+ struct ext3_extent newext;
+ struct ext4_ext_path *path;
+ /* start with a local allocated array without touching the inode */
+ struct ext3_extent_header *eh = (struct ext3_extent_header *)i_block;
+ (void)end_pblk;
+
+ newext.ee_block = start_blk;
+ newext.ee_len = end_blk - start_blk +1;
+ ext3_ext_store_pblock(&newext, start_pblk);
+
+ path = ext3_ext_find_extent(eh, start_blk, NULL);
+
+ if (!path)
+ return EXT2_ET_BLOCK_ALLOC_FAIL;
+
+ retval = ext3_ext_insert_extent(eh, path, &newext);
+
+ free(path);
+ return retval;
+}
+
+static void finish_range(struct list_blocks_struct *lb)
+{
+ int retval;
+
+ if (lb->first_block == 0)
+ return;
+
+ printf("(%lld-%lld):%u-%u\n", lb->first_bcnt, lb->last_bcnt,
+ lb->first_block, lb->last_block);
+
+ if (migrate) {
+ retval = build_extent(lb->first_bcnt, lb->last_bcnt,
+ lb->first_block, lb->last_block);
+ if (retval) {
+ com_err("build_extent", retval, ": Failed to build extent");
+ exit(1);
+ }
+ }
+
+ lb->first_block = 0;
+}
+/*
+ * We don't want to update the filesystem block bitmap
+ * directly. For indirect blocks and others which we need
+ * to mark as unused, we want to track them but not update
+ * the file systembitmap early. This is needed to make sure
+ * the subsequent request for free blocks are not satisfied
+ * by these indirect blocks. This makes sure that if
+ * we fail later writing the inode, we have consistent
+ * block bitmap.
+ */
+
+static int mark_block_bitmap(ext4_fsblk_t pblock)
+{
+ struct blk_stat *stat;
+
+ stat = malloc(sizeof(struct blk_stat));
+ if (!stat) {
+ return EXT2_ET_BLOCK_ALLOC_FAIL;
+ }
+
+ stat->pblock = pblock;
+ stat->dirty = 1;
+ list_add(&(stat->head), &blk_stat_head);
+
+ return 0;
+
+
+}
+static int unmark_block_bitmap(ext4_fsblk_t pblock)
+{
+ struct blk_stat *stat;
+
+ stat = malloc(sizeof(struct blk_stat));
+ if (!stat) {
+ return EXT2_ET_BLOCK_ALLOC_FAIL;
+ }
+
+ stat->pblock = pblock;
+ stat->dirty = 0;
+ list_add(&(stat->head), &blk_stat_head);
+
+ return 0;
+}
+
+static int write_block_bitmap()
+{
+ struct blk_stat *stat;
+ struct list_head *entry;
+
+ list_for_each(entry, &blk_stat_head) {
+
+ stat = list_entry(entry, struct blk_stat, head);
+ if (stat->dirty) {
+ ext2fs_mark_block_bitmap(current_fs->block_map, stat->pblock);
+ } else {
+ ext2fs_unmark_block_bitmap(current_fs->block_map, stat->pblock);
+ }
+ }
+
+ ext2fs_mark_bb_dirty(current_fs);
+
+ return ext2fs_write_block_bitmap(current_fs);
+}
+
+
+static int list_blocks_proc(ext2_filsys fs EXT2FS_ATTR((unused)),
+ blk_t *blocknr, e2_blkcnt_t blockcnt,
+ blk_t ref_block EXT2FS_ATTR((unused)),
+ int ref_offset EXT2FS_ATTR((unused)),
+ void *private)
+{
+ struct list_blocks_struct *lb = (struct list_blocks_struct *) private;
+
+ if (blockcnt >= 0) {
+ /*
+ * See if we can add on to the existing range (if it exists)
+ */
+ if (lb->first_block &&
+ (lb->last_block+1 == *blocknr) &&
+ (lb->last_bcnt+1 == blockcnt)) {
+ lb->last_block = *blocknr;
+ lb->last_bcnt = blockcnt;
+ return 0;
+ }
+ /*
+ * Start a new range.
+ */
+ finish_range(lb);
+ lb->first_block = lb->last_block = *blocknr;
+ lb->first_bcnt = lb->last_bcnt = blockcnt;
+ } else {
+ /*
+ * special blocks such as indirect, double indrect and triple
+ * indirect blocks. Mark them as free if we are migrating
+ * BLOCK_COUNT_IND BLOCK_COUNT_DIND BLOCK_COUNT_TIND
+ */
+ if (migrate) {
+ if (unmark_block_bitmap(*blocknr))
+ return BLOCK_ABORT;
+ }
+ }
+
+ return 0;
+}
+
+static void iterate_blocks(ext2_filsys current_fs, ext2_ino_t inode_num)
+{
+ struct list_blocks_struct lb;
+ lb.first_block = 0;
+
+ ext2fs_block_iterate2(current_fs, inode_num, 0, NULL, list_blocks_proc, (void *)&lb);
+
+ finish_range(&lb);
+}
+
+/*FIXME!! goal value passed as zero */
+
+/* FIXME!! 48 bit block
+ * Can we ask for block addressed by 48 bit ?
+ * We have actually mounted a ext3 file system via ext4dev If want want
+ * we will have to change the group descriptor also */
+/* Function is also called from extents.c */
+static struct blk_cache * __get_block(ext2_filsys current_fs, ext4_fsblk_t pblock)
+{
+ struct list_head *entry;
+ struct blk_cache *blk;
+ void *addr;
+ int retval;
+ /* need to initialize to fix corruption due to (long) typecasting */
+ ext4_fsblk_t block = 0;
+
+
+ if (pblock == 0) {
+ /* allocate in disk and give back */
+ /* FIXME!! 48 bit block */
+ retval = ext2fs_new_block(current_fs, 0, NULL, (blk_t *)&block);
+ if (retval) {
+ /*
+ * In case we fail we don't write/sync previous update
+ * we don't want partial conversion
+ */
+ return NULL;
+ }
+ if (mark_block_bitmap(block))
+ return NULL;
+
+ addr = malloc(current_fs->blocksize);
+ if (!addr)
+ return NULL;
+ memset(addr, 0, current_fs->blocksize);
+
+ blk = malloc(sizeof(struct blk_cache));
+ if (!blk) {
+ free(addr);
+ return NULL;
+ }
+
+ blk->pblock = (ext4_fsblk_t)block;
+ blk->block_mem_addr = addr;
+ list_add(&(blk->head), &blk_cache_head);
+
+ return blk;
+ }
+
+
+ list_for_each(entry, &blk_cache_head) {
+
+ blk = list_entry(entry, struct blk_cache, head);
+
+ if (blk->pblock == pblock ) {
+ return blk;
+
+ }
+ }
+
+ /*
+ * No block present. Allocate a disk block and a memory equivalent
+ * add the same to the list and return the address
+ */
+
+ /* FIXME!! 48 bit block */
+ retval = ext2fs_new_block(current_fs, 0, NULL, (blk_t *)&block);
+ if (retval) {
+ /*
+ * In case we fail we don't write/sync previous update
+ * we don't want partial conversion
+ */
+ return NULL;
+ }
+ if (mark_block_bitmap(block))
+ return NULL;
+
+ addr = malloc(current_fs->blocksize);
+ if (!addr)
+ return NULL;
+ memset(addr, 0, current_fs->blocksize);
+
+ blk = malloc(sizeof(struct blk_cache));
+ if (!blk) {
+ free(addr);
+ return NULL;
+ }
+
+ blk->pblock = (ext4_fsblk_t)block;
+ blk->block_mem_addr = addr;
+ list_add(&(blk->head), &blk_cache_head);
+
+ return blk;
+
+}
+
+struct blk_cache * get_block(ext4_fsblk_t pblock)
+{
+
+ return __get_block(current_fs, pblock);
+}
+
+static int write_extent_block(ext2_filsys current_fs, ext4_fsblk_t pblock, void *buf)
+{
+ struct ext3_extent_header *eh = (struct ext3_extent_header *)buf;
+ struct ext3_extent_idx *ix;
+ ext4_fsblk_t tpblock;
+ struct blk_cache *blkc;
+ int i, retval;
+
+ if (eh->eh_depth == 0) {
+ retval = ext2fs_write_ext_block(current_fs, pblock, buf);
+ if (retval)
+ goto err_out;
+ } else {
+ ix = EXT_FIRST_INDEX(eh);
+ for (i = 0; i < eh->eh_entries; i++, ix++) {
+
+ tpblock = idx_pblock(ix);
+ blkc = get_block(tpblock);
+ if (!blkc) {
+ retval = EXT2_ET_BLOCK_ALLOC_FAIL;
+ goto err_out;
+ }
+ retval = write_extent_block(current_fs, blkc->pblock, blkc->block_mem_addr);
+ if (retval) {
+ goto err_out;
+ }
+ }
+ }
+
+err_out:
+
+ return retval;
+
+}
+
+
+static int write_extent_details(ext2_filsys current_fs, ext2_ino_t inode_num,
+ struct ext2_inode *inode, blk_t *i_block)
+{
+
+ struct ext3_extent_header *eh = (struct ext3_extent_header *)i_block;
+ struct ext3_extent_idx *ix;
+ ext4_fsblk_t pblock;
+ struct blk_cache *blkc;
+ int i, retval;
+
+
+ /* Write the blocks to the disk */
+ if (eh->eh_depth != 0) {
+ /* need to write blocks corresponding to extent_idx */
+ ix = EXT_FIRST_INDEX(eh);
+ for (i = 0; i < eh->eh_entries; i++, ix++) {
+
+ pblock = idx_pblock(ix);
+ blkc = get_block(pblock);
+ if (!blkc) {
+ retval = EXT2_ET_BLOCK_ALLOC_FAIL;
+ goto err_out;
+ }
+ retval = write_extent_block(current_fs, blkc->pblock, blkc->block_mem_addr);
+ if (retval) {
+ goto err_out;
+ }
+ }
+ }
+
+ inode->i_flags |= EXT4_EXTENTS_FL;
+ memcpy(inode->i_block, i_block, sizeof(inode->i_block));
+ /* write inode */
+ retval = ext2fs_write_inode(current_fs, inode_num, inode);
+ if (retval) {
+ goto err_out;
+ }
+
+ /*
+ * write the updated block bit map at the end
+ * so that we don't need to reset the bitmap later
+ * if something fails
+ */
+
+ retval = write_block_bitmap();
+ if (retval) {
+ goto err_out;
+ }
+
+ if (!(current_fs->super->s_feature_incompat & EXT3_FEATURE_INCOMPAT_EXTENTS)) {
+ current_fs->super->s_feature_incompat |= EXT3_FEATURE_INCOMPAT_EXTENTS;
+
+ /* FIXME!! should we write super block */
+ ext2fs_mark_super_dirty(current_fs);
+ }
+
+err_out:
+ return retval;
+
+}
+
+main(int argc, char *argv[])
+{
+ char *dev_name, *file_name;
+ int flags, superblock = 0;
+ unsigned int block_size = 0;
+ ext2_ino_t inode_num;
+ struct ext2_inode inode;
+ int retval;
+
+ if (argc < 3 || argc > 4) {
+ usage(argv[0]);
+ }
+
+ blk_init();
+ inode_i_block_init();
+
+ if (argc == 3 ) {
+ dev_name = argv[1];
+ file_name = argv[2];
+ } else {
+ if (strcmp(argv[1], "--migrate") == 0) {
+ migrate = 1;
+ } else if (strcmp(argv[1], "--display") == 0) {
+ migrate = 0;
+ } else {
+ usage(argv[0]);
+ }
+ dev_name = argv[2];
+ file_name = argv[3];
+ }
+
+ if (migrate) {
+ flags = EXT2_FLAG_SOFTSUPP_FEATURES | EXT2_FLAG_RW | EXT2_FLAG_SUPER_ONLY | EXT2_FLAG_MASTER_SB_ONLY;
+ } else {
+ flags = EXT2_FLAG_SOFTSUPP_FEATURES;
+ }
+
+ retval = ext2fs_open(dev_name, flags, superblock,
+ block_size, unix_io_manager, &current_fs);
+ if (retval) {
+ com_err(dev_name, retval,": Unable to open the file system");
+ return;
+ }
+
+ retval = ext2fs_read_inode_bitmap(current_fs);
+ if (retval) {
+ com_err(dev_name, retval,": Unable to read inode bitmap");
+ goto err_out;
+ }
+ retval = ext2fs_read_block_bitmap(current_fs);
+ if (retval) {
+ com_err(dev_name, retval,": Unable to read block bitmap");
+ goto err_out;
+ }
+
+ retval = ext2fs_namei(current_fs, EXT2_ROOT_INO,
+ EXT2_ROOT_INO, file_name, &inode_num);
+ if (retval) {
+ com_err(file_name, retval,": Unable to get file inode number");
+ goto err_out;
+ }
+
+ printf("Inode number %d\n", inode_num);
+
+ retval = ext2fs_read_inode(current_fs, inode_num, &inode);
+ if (retval) {
+ com_err(file_name, retval,": Unable to get file inode number");
+ goto err_out;
+ }
+
+ if (inode.i_flags & EXT4_EXTENTS_FL) {
+ printf("Extent enabled\n");
+ migrate = 0 ;
+ }
+
+ iterate_blocks(current_fs, inode_num);
+
+ if (migrate) {
+
+ /*
+ * Only if we have successfully walked the block mapping write the extent details
+ */
+ retval = write_extent_details(current_fs, inode_num, &inode, i_block);
+ if (retval) {
+ com_err("write_extent_details", 0, "Failed to write extent details");
+ goto err_out;
+ }
+
+ /* dump the migrated extent details */
+ migrate = 0;
+ printf("Extent details after migrate\n");
+ iterate_blocks(current_fs, inode_num);
+ }
+
+err_out:
+ ext2fs_close(current_fs);
+
+}
diff --git a/ext4migrate/migrate.h b/ext4migrate/migrate.h
new file mode 100644
index 0000000..4b00f99
--- /dev/null
+++ b/ext4migrate/migrate.h
@@ -0,0 +1,27 @@
+
+#include "ext2fs/ext2_fs.h"
+#include "ext2fs/ext2fs.h"
+#include "ext2fs/kernel-list.h"
+
+typedef unsigned long long ext4_fsblk_t;
+
+extern ext2_filsys current_fs;
+
+#define EXT4_EXT_MAGIC 0xf30a
+
+struct list_blocks_struct {
+ blk_t first_block, last_block;
+ e2_blkcnt_t first_bcnt, last_bcnt;
+};
+
+struct blk_stat {
+ struct list_head head;
+ ext4_fsblk_t pblock;
+ int dirty;
+};
+
+struct blk_cache {
+ struct list_head head;
+ ext4_fsblk_t pblock;
+ void * block_mem_addr;
+};
--
1.5.1.rc3.30.ga8f4-dirty

2007-04-03 20:32:54

by Andreas Dilger

[permalink] [raw]
Subject: Re: [RFC][take 2] e2fsprogs: Add ext4migrate

On Apr 03, 2007 15:37 +0530, Aneesh Kumar K.V wrote:
> The extent insert code is derived out of the latest ext4 kernel
> source. I have tried to keep the code as close as possible to the
> kernel sources. This makes sure that any fixes for the tree building
> code in kernel should be easily applied to ext4migrate. The ext3_ext
> naming convention instead of ext4_ext found in kernel is to make sure
> we are in sync with rest of e2fsprogs source.

Of course, the other way to do this would be to temporarily mount the
filesystem as ext4, copy non-extent files via "cp" (can use lsattr to
check for extent flag) and then rename new file over old one. Care
must be taken to not mount filesystem on "visible" mountpoint, so that
users cannot be changing the filesystem while copy is being done.

This can be done to convert an ext4 filesystem back to ext3 also, if
the ext4 filesystem is mounted with "noextents" (to disable creation
of new files with extent mapping).

The only minor issue is that the inode numbers of the files will change.

> The inode modification is done only at the last stage. This is to make
> sure that if we fail at any intermediate stage, we exit without touching
> the disk.
>
> The inode update is done as below
> a) Walk the extent index blocks and write them to the disk. If failed exit
> b) Write the inode. if failed exit.
> c) Write the updated block bitmap. if failed exit ( This could be a problem
> because we have already updated the inode i_block filed to point to new
> blocks.). But such inconsistancy between inode i_block and block bitmap
> can be fixed by fsck IIUC.

Why not mark all the relevant blocks in use (for both exent- and block-mapped
copies) until the copy is done, then write everything out, and only mark the
block-mapped file blocks free after the inode is written to disk? This avoids
the danger that the new extent-mapped file's blocks are marked free and get
double-allocated (corrupting the file data, possibly the whole filesystem).

I don't think there is a guarantee that an impatient user will run a lengthy
e2fsck after interrupting the migrate. Also, you should mark the filesystem
unclean at first change unless everything completes successfully. That way
e2fsck will at least run automatically on the next boot.


Other general notes:
- wrap lines at 80 columns
- would be good to have a "-R" mode that walked the whole filesystem,
since startup time is very long for large filesystems
- also allow specifying multiple files on the command-line
- changing the operation to be multi-file allows avoiding sync of bitmaps
two times (once after extents are allocated and inode written, once after
indirect blocks are freed). There only needs to be one sync per file.

Cheers, Andreas
--
Andreas Dilger
Principal Software Engineer
Cluster File Systems, Inc.

2007-04-04 08:00:43

by Aneesh Kumar K.V

[permalink] [raw]
Subject: Re: [RFC][take 2] e2fsprogs: Add ext4migrate



Andreas Dilger wrote:
> On Apr 03, 2007 15:37 +0530, Aneesh Kumar K.V wrote:
>> The extent insert code is derived out of the latest ext4 kernel
>> source. I have tried to keep the code as close as possible to the
>> kernel sources. This makes sure that any fixes for the tree building
>> code in kernel should be easily applied to ext4migrate. The ext3_ext
>> naming convention instead of ext4_ext found in kernel is to make sure
>> we are in sync with rest of e2fsprogs source.
>
> Of course, the other way to do this would be to temporarily mount the
> filesystem as ext4, copy non-extent files via "cp" (can use lsattr to
> check for extent flag) and then rename new file over old one. Care
> must be taken to not mount filesystem on "visible" mountpoint, so that
> users cannot be changing the filesystem while copy is being done.
>
> This can be done to convert an ext4 filesystem back to ext3 also, if
> the ext4 filesystem is mounted with "noextents" (to disable creation
> of new files with extent mapping).
>
> The only minor issue is that the inode numbers of the files will change.
>

One also need to make sure that the hard links are not broken by such
copy. Also when using copy we are touching the data blocks. And for
large files the copy operations could take quiet a lot of time. With the
patches I sent we are not touching/relocating the data blocks. We are
only converting the meta data. This results in a faster migration.




>> The inode modification is done only at the last stage. This is to make
>> sure that if we fail at any intermediate stage, we exit without touching
>> the disk.
>>
>> The inode update is done as below
>> a) Walk the extent index blocks and write them to the disk. If failed exit
>> b) Write the inode. if failed exit.
>> c) Write the updated block bitmap. if failed exit ( This could be a problem
>> because we have already updated the inode i_block filed to point to new
>> blocks.). But such inconsistancy between inode i_block and block bitmap
>> can be fixed by fsck IIUC.
>
> Why not mark all the relevant blocks in use (for both exent- and block-mapped
> copies) until the copy is done, then write everything out, and only mark the
> block-mapped file blocks free after the inode is written to disk? This avoids
> the danger that the new extent-mapped file's blocks are marked free and get
> double-allocated (corrupting the file data, possibly the whole filesystem).
>

Will do this .



> I don't think there is a guarantee that an impatient user will run a lengthy
> e2fsck after interrupting the migrate. Also, you should mark the filesystem
> unclean at first change unless everything completes successfully. That way
> e2fsck will at least run automatically on the next boot.
>
>


Will do this


> Other general notes:
> - wrap lines at 80 columns
> - would be good to have a "-R" mode that walked the whole filesystem,
> since startup time is very long for large filesystems
> - also allow specifying multiple files on the command-line
> - changing the operation to be multi-file allows avoiding sync of bitmaps
> two times (once after extents are allocated and inode written, once after
> indirect blocks are freed). There only needs to be one sync per file.
>


Will do this in the next patch




-aneesh