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Date: Fri, 03 Oct 2008 14:21:55 +0200
From: Frédéric Bohé <frederic.bohe@...l.net>
To: "linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] ext4: remove usage of Uptodate flag to initialize
buddy after an online resize
Please hold on with this patch. There is a race condition somewhere. I
will investigated more and send a new patch later.
Le mercredi 01 octobre 2008 à 16:44 +0200, Frédéric Bohé a écrit :
> From: Frederic Bohe <frederic.bohe@...l.net>
>
> Replace Page cache's uptodate flag by ext4_group_info's
> EXT4_GROUP_INFO_NEED_INIT_BIT flags to allow extended group's buddy and
> added groups' buddy to be initialized or re-initialized after an online
> resize.
>
> Signed-off-by: Frederic Bohe <frederic.bohe@...l.net>
> ---
> ext4.h | 3 +-
> mballoc.c | 67 ++++++++++++--------------------------------------------------
> resize.c | 49 +++++----------------------------------------
> 3 files changed, 21 insertions(+), 98 deletions(-)
>
> Index: linux/fs/ext4/ext4.h
> ===================================================================
> --- linux.orig/fs/ext4/ext4.h 2008-10-01 14:14:01.000000000 +0200
> +++ linux/fs/ext4/ext4.h 2008-10-01 14:14:51.000000000 +0200
> @@ -1070,7 +1070,8 @@ extern int __init init_ext4_mballoc(void
> extern void exit_ext4_mballoc(void);
> extern void ext4_mb_free_blocks(handle_t *, struct inode *,
> unsigned long, unsigned long, int, unsigned long *);
> -extern int ext4_mb_add_more_groupinfo(struct super_block *sb,
> +extern void ext4_mb_set_need_init_bit(struct ext4_group_info *);
> +extern int ext4_mb_add_groupinfo(struct super_block *sb,
> ext4_group_t i, struct ext4_group_desc *desc);
> extern void ext4_mb_update_group_info(struct ext4_group_info *grp,
> ext4_grpblk_t add);
> Index: linux/fs/ext4/mballoc.c
> ===================================================================
> --- linux.orig/fs/ext4/mballoc.c 2008-10-01 14:15:02.000000000 +0200
> +++ linux/fs/ext4/mballoc.c 2008-10-01 15:49:32.000000000 +0200
> @@ -918,13 +918,15 @@ ext4_mb_load_buddy(struct super_block *s
> /* we could use find_or_create_page(), but it locks page
> * what we'd like to avoid in fast path ... */
> page = find_get_page(inode->i_mapping, pnum);
> - if (page == NULL || !PageUptodate(page)) {
> + if (page == NULL || !PageUptodate(page) ||
> + EXT4_MB_GRP_NEED_INIT(e4b->bd_info)) {
> if (page)
> page_cache_release(page);
> page = find_or_create_page(inode->i_mapping, pnum, GFP_NOFS);
> if (page) {
> BUG_ON(page->mapping != inode->i_mapping);
> - if (!PageUptodate(page)) {
> + if (!PageUptodate(page) ||
> + EXT4_MB_GRP_NEED_INIT(e4b->bd_info)) {
> ret = ext4_mb_init_cache(page, NULL);
> if (ret) {
> unlock_page(page);
> @@ -949,13 +951,15 @@ ext4_mb_load_buddy(struct super_block *s
> poff = block % blocks_per_page;
>
> page = find_get_page(inode->i_mapping, pnum);
> - if (page == NULL || !PageUptodate(page)) {
> + if (page == NULL || !PageUptodate(page) ||
> + EXT4_MB_GRP_NEED_INIT(e4b->bd_info)) {
> if (page)
> page_cache_release(page);
> page = find_or_create_page(inode->i_mapping, pnum, GFP_NOFS);
> if (page) {
> BUG_ON(page->mapping != inode->i_mapping);
> - if (!PageUptodate(page)) {
> + if (!PageUptodate(page) ||
> + EXT4_MB_GRP_NEED_INIT(e4b->bd_info)) {
> ret = ext4_mb_init_cache(page, e4b->bd_bitmap);
> if (ret) {
> unlock_page(page);
> @@ -2240,6 +2244,10 @@ ext4_mb_store_history(struct ext4_alloca
> #define ext4_mb_history_init(sb)
> #endif
>
> +void ext4_mb_set_need_init_bit(struct ext4_group_info *grp)
> +{
> + set_bit(EXT4_GROUP_INFO_NEED_INIT_BIT, &(grp->bb_state));
> +}
>
> /* Create and initialize ext4_group_info data for the given group. */
> int ext4_mb_add_groupinfo(struct super_block *sb, ext4_group_t group,
> @@ -2284,8 +2292,7 @@ int ext4_mb_add_groupinfo(struct super_b
> printk(KERN_ERR "EXT4-fs: can't allocate buddy mem\n");
> goto exit_group_info;
> }
> - set_bit(EXT4_GROUP_INFO_NEED_INIT_BIT,
> - &(meta_group_info[i]->bb_state));
> + ext4_mb_set_need_init_bit(meta_group_info[i]);
>
> /*
> * initialize bb_free to be able to skip
> @@ -2326,54 +2333,6 @@ exit_meta_group_info:
> } /* ext4_mb_add_groupinfo */
>
> /*
> - * Add a group to the existing groups.
> - * This function is used for online resize
> - */
> -int ext4_mb_add_more_groupinfo(struct super_block *sb, ext4_group_t group,
> - struct ext4_group_desc *desc)
> -{
> - struct ext4_sb_info *sbi = EXT4_SB(sb);
> - struct inode *inode = sbi->s_buddy_cache;
> - int blocks_per_page;
> - int block;
> - int pnum;
> - struct page *page;
> - int err;
> -
> - /* Add group based on group descriptor*/
> - err = ext4_mb_add_groupinfo(sb, group, desc);
> - if (err)
> - return err;
> -
> - /*
> - * Cache pages containing dynamic mb_alloc datas (buddy and bitmap
> - * datas) are set not up to date so that they will be re-initilaized
> - * during the next call to ext4_mb_load_buddy
> - */
> -
> - /* Set buddy page as not up to date */
> - blocks_per_page = PAGE_CACHE_SIZE / sb->s_blocksize;
> - block = group * 2;
> - pnum = block / blocks_per_page;
> - page = find_get_page(inode->i_mapping, pnum);
> - if (page != NULL) {
> - ClearPageUptodate(page);
> - page_cache_release(page);
> - }
> -
> - /* Set bitmap page as not up to date */
> - block++;
> - pnum = block / blocks_per_page;
> - page = find_get_page(inode->i_mapping, pnum);
> - if (page != NULL) {
> - ClearPageUptodate(page);
> - page_cache_release(page);
> - }
> -
> - return 0;
> -}
> -
> -/*
> * Update an existing group.
> * This function is used for online resize
> */
> Index: linux/fs/ext4/resize.c
> ===================================================================
> --- linux.orig/fs/ext4/resize.c 2008-10-01 14:17:56.000000000 +0200
> +++ linux/fs/ext4/resize.c 2008-10-01 14:23:42.000000000 +0200
> @@ -870,7 +870,7 @@ int ext4_group_add(struct super_block *s
> * We can allocate memory for mb_alloc based on the new group
> * descriptor
> */
> - err = ext4_mb_add_more_groupinfo(sb, input->group, gdp);
> + err = ext4_mb_add_groupinfo(sb, input->group, gdp);
> if (err)
> goto exit_journal;
>
> @@ -1082,50 +1082,13 @@ int ext4_group_extend(struct super_block
> if ((err = ext4_journal_stop(handle)))
> goto exit_put;
>
> - /*
> - * Mark mballoc pages as not up to date so that they will be updated
> - * next time they are loaded by ext4_mb_load_buddy.
> - *
> - * XXX Bad, Bad, BAD!!! We should not be overloading the
> - * Uptodate flag, particularly on thte bitmap bh, as way of
> - * hinting to ext4_mb_load_buddy() that it needs to be
> - * overloaded. A user could take a LVM snapshot, then do an
> - * on-line fsck, and clear the uptodate flag, and this would
> - * not be a bug in userspace, but a bug in the kernel. FIXME!!!
> - */
> - {
> - struct ext4_sb_info *sbi = EXT4_SB(sb);
> - struct inode *inode = sbi->s_buddy_cache;
> - int blocks_per_page;
> - int block;
> - int pnum;
> - struct page *page;
> -
> - /* Set buddy page as not up to date */
> - blocks_per_page = PAGE_CACHE_SIZE / sb->s_blocksize;
> - block = group * 2;
> - pnum = block / blocks_per_page;
> - page = find_get_page(inode->i_mapping, pnum);
> - if (page != NULL) {
> - ClearPageUptodate(page);
> - page_cache_release(page);
> - }
> -
> - /* Set bitmap page as not up to date */
> - block++;
> - pnum = block / blocks_per_page;
> - page = find_get_page(inode->i_mapping, pnum);
> - if (page != NULL) {
> - ClearPageUptodate(page);
> - page_cache_release(page);
> - }
> + /* Get the info on the last group */
> + grp = ext4_get_group_info(sb, group);
>
> - /* Get the info on the last group */
> - grp = ext4_get_group_info(sb, group);
> + ext4_mb_set_need_init_bit(grp);
>
> - /* Update free blocks in group info */
> - ext4_mb_update_group_info(grp, add);
> - }
> + /* Update free blocks in group info */
> + ext4_mb_update_group_info(grp, add);
>
> if (test_opt(sb, DEBUG))
> printk(KERN_DEBUG "EXT4-fs: extended group to %llu blocks\n",
> --
>
>
> --
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