On Fri 01-05-09 09:55:59, Theodore Ts'o wrote:
> Ext4's on-line resizing adds a new block group and then, only at the
> last step adjusts s_groups_count. However, it's possible on SMP
> systems that another CPU could see the updated the s_group_count and
> not see the newly initialized data structures for the just-added block
> group. For this reason, it's important to insert a SMP read barrier
> after reading s_groups_count and before reading any (for example) the
> new block group descriptors allowed by the increased value of
> s_groups_count.
>
> Unfortunately, we rather blatently violate this locking protocol
> documented in fs/ext4/resize.c. Fortunately, (1) on-line resizes
> happen relatively rarely, and (2) it seems rare that the filesystem
> code will immediately try to use just-added block group before any
> memory ordering issues resolve themselves. So apparently problems
> here are relatively hard to hit, since ext3 has been vulnerable to the
> same issue for years with no one apparently complaining.
>
> Signed-off-by: "Theodore Ts'o" <tytso@xxxxxxx>
> ---
>
> Here's an updated version which uses a helper function to make sure we
> in the future we don't miss a place where smp_rmb() is needed.
Yeah, it looks nice. Maybe the code looks even better like this ;).
Acked-by: Jan Kara <jack@xxxxxxx>
Honza
> fs/ext4/balloc.c | 15 +++++++--------
> fs/ext4/ext4.h | 12 ++++++++++++
> fs/ext4/ialloc.c | 40 +++++++++++++++++++---------------------
> fs/ext4/inode.c | 7 ++++---
> fs/ext4/mballoc.c | 45 ++++++++++++++++++++++++---------------------
> fs/ext4/super.c | 3 +--
> 6 files changed, 67 insertions(+), 55 deletions(-)
>
> diff --git a/fs/ext4/balloc.c b/fs/ext4/balloc.c
> index 53c72ad..a5ba039 100644
> --- a/fs/ext4/balloc.c
> +++ b/fs/ext4/balloc.c
> @@ -88,6 +88,7 @@ unsigned ext4_init_block_bitmap(struct super_block *sb, struct buffer_head *bh,
> ext4_group_t block_group, struct ext4_group_desc *gdp)
> {
> int bit, bit_max;
> + ext4_group_t ngroups = ext4_get_groups_count(sb);
> unsigned free_blocks, group_blocks;
> struct ext4_sb_info *sbi = EXT4_SB(sb);
>
> @@ -123,7 +124,7 @@ unsigned ext4_init_block_bitmap(struct super_block *sb, struct buffer_head *bh,
> bit_max += ext4_bg_num_gdb(sb, block_group);
> }
>
> - if (block_group == sbi->s_groups_count - 1) {
> + if (block_group == ngroups - 1) {
> /*
> * Even though mke2fs always initialize first and last group
> * if some other tool enabled the EXT4_BG_BLOCK_UNINIT we need
> @@ -131,7 +132,7 @@ unsigned ext4_init_block_bitmap(struct super_block *sb, struct buffer_head *bh,
> */
> group_blocks = ext4_blocks_count(sbi->s_es) -
> le32_to_cpu(sbi->s_es->s_first_data_block) -
> - (EXT4_BLOCKS_PER_GROUP(sb) * (sbi->s_groups_count - 1));
> + (EXT4_BLOCKS_PER_GROUP(sb) * (ngroups - 1));
> } else {
> group_blocks = EXT4_BLOCKS_PER_GROUP(sb);
> }
> @@ -205,18 +206,18 @@ struct ext4_group_desc * ext4_get_group_desc(struct super_block *sb,
> {
> unsigned int group_desc;
> unsigned int offset;
> + ext4_group_t ngroups = ext4_get_groups_count(sb);
> struct ext4_group_desc *desc;
> struct ext4_sb_info *sbi = EXT4_SB(sb);
>
> - if (block_group >= sbi->s_groups_count) {
> + if (block_group >= ngroups) {
> ext4_error(sb, "ext4_get_group_desc",
> "block_group >= groups_count - "
> "block_group = %u, groups_count = %u",
> - block_group, sbi->s_groups_count);
> + block_group, ngroups);
>
> return NULL;
> }
> - smp_rmb();
>
> group_desc = block_group >> EXT4_DESC_PER_BLOCK_BITS(sb);
> offset = block_group & (EXT4_DESC_PER_BLOCK(sb) - 1);
> @@ -665,7 +666,7 @@ ext4_fsblk_t ext4_count_free_blocks(struct super_block *sb)
> ext4_fsblk_t desc_count;
> struct ext4_group_desc *gdp;
> ext4_group_t i;
> - ext4_group_t ngroups = EXT4_SB(sb)->s_groups_count;
> + ext4_group_t ngroups = ext4_get_groups_count(sb);
> #ifdef EXT4FS_DEBUG
> struct ext4_super_block *es;
> ext4_fsblk_t bitmap_count;
> @@ -677,7 +678,6 @@ ext4_fsblk_t ext4_count_free_blocks(struct super_block *sb)
> bitmap_count = 0;
> gdp = NULL;
>
> - smp_rmb();
> for (i = 0; i < ngroups; i++) {
> gdp = ext4_get_group_desc(sb, i, NULL);
> if (!gdp)
> @@ -700,7 +700,6 @@ ext4_fsblk_t ext4_count_free_blocks(struct super_block *sb)
> return bitmap_count;
> #else
> desc_count = 0;
> - smp_rmb();
> for (i = 0; i < ngroups; i++) {
> gdp = ext4_get_group_desc(sb, i, NULL);
> if (!gdp)
> diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
> index d0f15ef..02ec44b 100644
> --- a/fs/ext4/ext4.h
> +++ b/fs/ext4/ext4.h
> @@ -1228,6 +1228,18 @@ struct ext4_group_info *ext4_get_group_info(struct super_block *sb,
> return grp_info[indexv][indexh];
> }
>
> +/*
> + * Reading s_groups_count requires using smp_rmb() afterwards. See
> + * the locking protocol documented in the comments of ext4_group_add()
> + * in resize.c
> + */
> +static inline ext4_group_t ext4_get_groups_count(struct super_block *sb)
> +{
> + ext4_group_t ngroups = EXT4_SB(sb)->s_groups_count;
> +
> + smp_rmb();
> + return ngroups;
> +}
>
> static inline ext4_group_t ext4_flex_group(struct ext4_sb_info *sbi,
> ext4_group_t block_group)
> diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
> index f18e0a0..55ba419 100644
> --- a/fs/ext4/ialloc.c
> +++ b/fs/ext4/ialloc.c
> @@ -316,7 +316,7 @@ error_return:
> static int find_group_dir(struct super_block *sb, struct inode *parent,
> ext4_group_t *best_group)
> {
> - ext4_group_t ngroups = EXT4_SB(sb)->s_groups_count;
> + ext4_group_t ngroups = ext4_get_groups_count(sb);
> unsigned int freei, avefreei;
> struct ext4_group_desc *desc, *best_desc = NULL;
> ext4_group_t group;
> @@ -353,7 +353,7 @@ static int find_group_flex(struct super_block *sb, struct inode *parent,
> struct flex_groups *flex_group = sbi->s_flex_groups;
> ext4_group_t parent_group = EXT4_I(parent)->i_block_group;
> ext4_group_t parent_fbg_group = ext4_flex_group(sbi, parent_group);
> - ext4_group_t ngroups = sbi->s_groups_count;
> + ext4_group_t ngroups = ext4_get_groups_count(sb);
> int flex_size = ext4_flex_bg_size(sbi);
> ext4_group_t best_flex = parent_fbg_group;
> int blocks_per_flex = sbi->s_blocks_per_group * flex_size;
> @@ -362,7 +362,7 @@ static int find_group_flex(struct super_block *sb, struct inode *parent,
> ext4_group_t n_fbg_groups;
> ext4_group_t i;
>
> - n_fbg_groups = (sbi->s_groups_count + flex_size - 1) >>
> + n_fbg_groups = (ngroups + flex_size - 1) >>
> sbi->s_log_groups_per_flex;
>
> find_close_to_parent:
> @@ -478,20 +478,21 @@ static int find_group_orlov(struct super_block *sb, struct inode *parent,
> {
> ext4_group_t parent_group = EXT4_I(parent)->i_block_group;
> struct ext4_sb_info *sbi = EXT4_SB(sb);
> - ext4_group_t ngroups = sbi->s_groups_count;
> + ext4_group_t real_ngroups = ext4_get_groups_count(sb);
> int inodes_per_group = EXT4_INODES_PER_GROUP(sb);
> unsigned int freei, avefreei;
> ext4_fsblk_t freeb, avefreeb;
> unsigned int ndirs;
> int max_dirs, min_inodes;
> ext4_grpblk_t min_blocks;
> - ext4_group_t i, grp, g;
> + ext4_group_t i, grp, g, ngroups;
> struct ext4_group_desc *desc;
> struct orlov_stats stats;
> int flex_size = ext4_flex_bg_size(sbi);
>
> + ngroups = real_ngroups;
> if (flex_size > 1) {
> - ngroups = (ngroups + flex_size - 1) >>
> + ngroups = (real_ngroups + flex_size - 1) >>
> sbi->s_log_groups_per_flex;
> parent_group >>= sbi->s_log_groups_per_flex;
> }
> @@ -543,7 +544,7 @@ static int find_group_orlov(struct super_block *sb, struct inode *parent,
> */
> grp *= flex_size;
> for (i = 0; i < flex_size; i++) {
> - if (grp+i >= sbi->s_groups_count)
> + if (grp+i >= real_ngroups)
> break;
> desc = ext4_get_group_desc(sb, grp+i, NULL);
> if (desc && ext4_free_inodes_count(sb, desc)) {
> @@ -583,7 +584,7 @@ static int find_group_orlov(struct super_block *sb, struct inode *parent,
> }
>
> fallback:
> - ngroups = sbi->s_groups_count;
> + ngroups = real_ngroups;
> avefreei = freei / ngroups;
> fallback_retry:
> parent_group = EXT4_I(parent)->i_block_group;
> @@ -613,9 +614,8 @@ static int find_group_other(struct super_block *sb, struct inode *parent,
> ext4_group_t *group, int mode)
> {
> ext4_group_t parent_group = EXT4_I(parent)->i_block_group;
> - ext4_group_t ngroups = EXT4_SB(sb)->s_groups_count;
> + ext4_group_t i, last, ngroups = ext4_get_groups_count(sb);
> struct ext4_group_desc *desc;
> - ext4_group_t i, last;
> int flex_size = ext4_flex_bg_size(EXT4_SB(sb));
>
> /*
> @@ -799,11 +799,10 @@ struct inode *ext4_new_inode(handle_t *handle, struct inode *dir, int mode)
> struct super_block *sb;
> struct buffer_head *inode_bitmap_bh = NULL;
> struct buffer_head *group_desc_bh;
> - ext4_group_t group = 0;
> + ext4_group_t ngroups, group = 0;
> unsigned long ino = 0;
> struct inode *inode;
> struct ext4_group_desc *gdp = NULL;
> - struct ext4_super_block *es;
> struct ext4_inode_info *ei;
> struct ext4_sb_info *sbi;
> int ret2, err = 0;
> @@ -818,15 +817,14 @@ struct inode *ext4_new_inode(handle_t *handle, struct inode *dir, int mode)
> return ERR_PTR(-EPERM);
>
> sb = dir->i_sb;
> + ngroups = ext4_get_groups_count(sb);
> trace_mark(ext4_request_inode, "dev %s dir %lu mode %d", sb->s_id,
> dir->i_ino, mode);
> inode = new_inode(sb);
> if (!inode)
> return ERR_PTR(-ENOMEM);
> ei = EXT4_I(inode);
> -
> sbi = EXT4_SB(sb);
> - es = sbi->s_es;
>
> if (sbi->s_log_groups_per_flex && test_opt(sb, OLDALLOC)) {
> ret2 = find_group_flex(sb, dir, &group);
> @@ -856,7 +854,7 @@ got_group:
> if (ret2 == -1)
> goto out;
>
> - for (i = 0; i < sbi->s_groups_count; i++) {
> + for (i = 0; i < ngroups; i++) {
> err = -EIO;
>
> gdp = ext4_get_group_desc(sb, group, &group_desc_bh);
> @@ -917,7 +915,7 @@ repeat_in_this_group:
> * group descriptor metadata has not yet been updated.
> * So we just go onto the next blockgroup.
> */
> - if (++group == sbi->s_groups_count)
> + if (++group == ngroups)
> group = 0;
> }
> err = -ENOSPC;
> @@ -1158,7 +1156,7 @@ unsigned long ext4_count_free_inodes(struct super_block *sb)
> {
> unsigned long desc_count;
> struct ext4_group_desc *gdp;
> - ext4_group_t i;
> + ext4_group_t i, ngroups = ext4_get_groups_count(sb);
> #ifdef EXT4FS_DEBUG
> struct ext4_super_block *es;
> unsigned long bitmap_count, x;
> @@ -1168,7 +1166,7 @@ unsigned long ext4_count_free_inodes(struct super_block *sb)
> desc_count = 0;
> bitmap_count = 0;
> gdp = NULL;
> - for (i = 0; i < EXT4_SB(sb)->s_groups_count; i++) {
> + for (i = 0; i < ngroups; i++) {
> gdp = ext4_get_group_desc(sb, i, NULL);
> if (!gdp)
> continue;
> @@ -1190,7 +1188,7 @@ unsigned long ext4_count_free_inodes(struct super_block *sb)
> return desc_count;
> #else
> desc_count = 0;
> - for (i = 0; i < EXT4_SB(sb)->s_groups_count; i++) {
> + for (i = 0; i < ngroups; i++) {
> gdp = ext4_get_group_desc(sb, i, NULL);
> if (!gdp)
> continue;
> @@ -1205,9 +1203,9 @@ unsigned long ext4_count_free_inodes(struct super_block *sb)
> unsigned long ext4_count_dirs(struct super_block * sb)
> {
> unsigned long count = 0;
> - ext4_group_t i;
> + ext4_group_t i, ngroups = ext4_get_groups_count(sb);
>
> - for (i = 0; i < EXT4_SB(sb)->s_groups_count; i++) {
> + for (i = 0; i < ngroups; i++) {
> struct ext4_group_desc *gdp = ext4_get_group_desc(sb, i, NULL);
> if (!gdp)
> continue;
> diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
> index b891045..3e90965 100644
> --- a/fs/ext4/inode.c
> +++ b/fs/ext4/inode.c
> @@ -4916,7 +4916,8 @@ static int ext4_index_trans_blocks(struct inode *inode, int nrblocks, int chunk)
> */
> int ext4_meta_trans_blocks(struct inode *inode, int nrblocks, int chunk)
> {
> - int groups, gdpblocks;
> + ext4_group_t groups, ngroups = ext4_get_groups_count(inode->i_sb);
> + int gdpblocks;
> int idxblocks;
> int ret = 0;
>
> @@ -4943,8 +4944,8 @@ int ext4_meta_trans_blocks(struct inode *inode, int nrblocks, int chunk)
> groups += nrblocks;
>
> gdpblocks = groups;
> - if (groups > EXT4_SB(inode->i_sb)->s_groups_count)
> - groups = EXT4_SB(inode->i_sb)->s_groups_count;
> + if (groups > ngroups)
> + groups = ngroups;
> if (groups > EXT4_SB(inode->i_sb)->s_gdb_count)
> gdpblocks = EXT4_SB(inode->i_sb)->s_gdb_count;
>
> diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> index f871677..c3af9e6 100644
> --- a/fs/ext4/mballoc.c
> +++ b/fs/ext4/mballoc.c
> @@ -739,6 +739,7 @@ static void ext4_mb_generate_buddy(struct super_block *sb,
>
> static int ext4_mb_init_cache(struct page *page, char *incore)
> {
> + ext4_group_t ngroups;
> int blocksize;
> int blocks_per_page;
> int groups_per_page;
> @@ -757,6 +758,7 @@ static int ext4_mb_init_cache(struct page *page, char *incore)
>
> inode = page->mapping->host;
> sb = inode->i_sb;
> + ngroups = ext4_get_groups_count(sb);
> blocksize = 1 << inode->i_blkbits;
> blocks_per_page = PAGE_CACHE_SIZE / blocksize;
>
> @@ -780,7 +782,7 @@ static int ext4_mb_init_cache(struct page *page, char *incore)
> for (i = 0; i < groups_per_page; i++) {
> struct ext4_group_desc *desc;
>
> - if (first_group + i >= EXT4_SB(sb)->s_groups_count)
> + if (first_group + i >= ngroups)
> break;
>
> err = -EIO;
> @@ -852,7 +854,7 @@ static int ext4_mb_init_cache(struct page *page, char *incore)
> struct ext4_group_info *grinfo;
>
> group = (first_block + i) >> 1;
> - if (group >= EXT4_SB(sb)->s_groups_count)
> + if (group >= ngroups)
> break;
>
> /*
> @@ -1788,6 +1790,7 @@ int ext4_mb_get_buddy_cache_lock(struct super_block *sb, ext4_group_t group)
> int block, pnum;
> int blocks_per_page;
> int groups_per_page;
> + ext4_group_t ngroups = ext4_get_groups_count(sb);
> ext4_group_t first_group;
> struct ext4_group_info *grp;
>
> @@ -1807,7 +1810,7 @@ int ext4_mb_get_buddy_cache_lock(struct super_block *sb, ext4_group_t group)
> /* read all groups the page covers into the cache */
> for (i = 0; i < groups_per_page; i++) {
>
> - if ((first_group + i) >= EXT4_SB(sb)->s_groups_count)
> + if ((first_group + i) >= ngroups)
> break;
> grp = ext4_get_group_info(sb, first_group + i);
> /* take all groups write allocation
> @@ -1945,8 +1948,7 @@ err:
> static noinline_for_stack int
> ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
> {
> - ext4_group_t group;
> - ext4_group_t i;
> + ext4_group_t ngroups, group, i;
> int cr;
> int err = 0;
> int bsbits;
> @@ -1957,6 +1959,7 @@ ext4_mb_regular_allocator(struct ext4_allocation_context *ac)
>
> sb = ac->ac_sb;
> sbi = EXT4_SB(sb);
> + ngroups = ext4_get_groups_count(sb);
> BUG_ON(ac->ac_status == AC_STATUS_FOUND);
>
> /* first, try the goal */
> @@ -2017,11 +2020,11 @@ repeat:
> */
> group = ac->ac_g_ex.fe_group;
>
> - for (i = 0; i < EXT4_SB(sb)->s_groups_count; group++, i++) {
> + for (i = 0; i < ngroups; group++, i++) {
> struct ext4_group_info *grp;
> struct ext4_group_desc *desc;
>
> - if (group == EXT4_SB(sb)->s_groups_count)
> + if (group == ngroups)
> group = 0;
>
> /* quick check to skip empty groups */
> @@ -2315,12 +2318,10 @@ static struct file_operations ext4_mb_seq_history_fops = {
> static void *ext4_mb_seq_groups_start(struct seq_file *seq, loff_t *pos)
> {
> struct super_block *sb = seq->private;
> - struct ext4_sb_info *sbi = EXT4_SB(sb);
> ext4_group_t group;
>
> - if (*pos < 0 || *pos >= sbi->s_groups_count)
> + if (*pos < 0 || *pos >= ext4_get_groups_count(sb))
> return NULL;
> -
> group = *pos + 1;
> return (void *) ((unsigned long) group);
> }
> @@ -2328,11 +2329,10 @@ static void *ext4_mb_seq_groups_start(struct seq_file *seq, loff_t *pos)
> static void *ext4_mb_seq_groups_next(struct seq_file *seq, void *v, loff_t *pos)
> {
> struct super_block *sb = seq->private;
> - struct ext4_sb_info *sbi = EXT4_SB(sb);
> ext4_group_t group;
>
> ++*pos;
> - if (*pos < 0 || *pos >= sbi->s_groups_count)
> + if (*pos < 0 || *pos >= ext4_get_groups_count(sb))
> return NULL;
> group = *pos + 1;
> return (void *) ((unsigned long) group);
> @@ -2587,6 +2587,7 @@ void ext4_mb_update_group_info(struct ext4_group_info *grp, ext4_grpblk_t add)
>
> static int ext4_mb_init_backend(struct super_block *sb)
> {
> + ext4_group_t ngroups = ext4_get_groups_count(sb);
> ext4_group_t i;
> int metalen;
> struct ext4_sb_info *sbi = EXT4_SB(sb);
> @@ -2598,7 +2599,7 @@ static int ext4_mb_init_backend(struct super_block *sb)
> struct ext4_group_desc *desc;
>
> /* This is the number of blocks used by GDT */
> - num_meta_group_infos = (sbi->s_groups_count + EXT4_DESC_PER_BLOCK(sb) -
> + num_meta_group_infos = (ngroups + EXT4_DESC_PER_BLOCK(sb) -
> 1) >> EXT4_DESC_PER_BLOCK_BITS(sb);
>
> /*
> @@ -2644,7 +2645,7 @@ static int ext4_mb_init_backend(struct super_block *sb)
> for (i = 0; i < num_meta_group_infos; i++) {
> if ((i + 1) == num_meta_group_infos)
> metalen = sizeof(*meta_group_info) *
> - (sbi->s_groups_count -
> + (ngroups -
> (i << EXT4_DESC_PER_BLOCK_BITS(sb)));
> meta_group_info = kmalloc(metalen, GFP_KERNEL);
> if (meta_group_info == NULL) {
> @@ -2655,7 +2656,7 @@ static int ext4_mb_init_backend(struct super_block *sb)
> sbi->s_group_info[i] = meta_group_info;
> }
>
> - for (i = 0; i < sbi->s_groups_count; i++) {
> + for (i = 0; i < ngroups; i++) {
> desc = ext4_get_group_desc(sb, i, NULL);
> if (desc == NULL) {
> printk(KERN_ERR
> @@ -2781,13 +2782,14 @@ static void ext4_mb_cleanup_pa(struct ext4_group_info *grp)
>
> int ext4_mb_release(struct super_block *sb)
> {
> + ext4_group_t ngroups = ext4_get_groups_count(sb);
> ext4_group_t i;
> int num_meta_group_infos;
> struct ext4_group_info *grinfo;
> struct ext4_sb_info *sbi = EXT4_SB(sb);
>
> if (sbi->s_group_info) {
> - for (i = 0; i < sbi->s_groups_count; i++) {
> + for (i = 0; i < ngroups; i++) {
> grinfo = ext4_get_group_info(sb, i);
> #ifdef DOUBLE_CHECK
> kfree(grinfo->bb_bitmap);
> @@ -2797,7 +2799,7 @@ int ext4_mb_release(struct super_block *sb)
> ext4_unlock_group(sb, i);
> kfree(grinfo);
> }
> - num_meta_group_infos = (sbi->s_groups_count +
> + num_meta_group_infos = (ngroups +
> EXT4_DESC_PER_BLOCK(sb) - 1) >>
> EXT4_DESC_PER_BLOCK_BITS(sb);
> for (i = 0; i < num_meta_group_infos; i++)
> @@ -4121,7 +4123,7 @@ static void ext4_mb_return_to_preallocation(struct inode *inode,
> static void ext4_mb_show_ac(struct ext4_allocation_context *ac)
> {
> struct super_block *sb = ac->ac_sb;
> - ext4_group_t i;
> + ext4_group_t ngroups, i;
>
> printk(KERN_ERR "EXT4-fs: Can't allocate:"
> " Allocation context details:\n");
> @@ -4145,7 +4147,8 @@ static void ext4_mb_show_ac(struct ext4_allocation_context *ac)
> printk(KERN_ERR "EXT4-fs: %lu scanned, %d found\n", ac->ac_ex_scanned,
> ac->ac_found);
> printk(KERN_ERR "EXT4-fs: groups: \n");
> - for (i = 0; i < EXT4_SB(sb)->s_groups_count; i++) {
> + ngroups = ext4_get_groups_count(sb);
> + for (i = 0; i < ngroups; i++) {
> struct ext4_group_info *grp = ext4_get_group_info(sb, i);
> struct ext4_prealloc_space *pa;
> ext4_grpblk_t start;
> @@ -4469,13 +4472,13 @@ static int ext4_mb_release_context(struct ext4_allocation_context *ac)
>
> static int ext4_mb_discard_preallocations(struct super_block *sb, int needed)
> {
> - ext4_group_t i;
> + ext4_group_t i, ngroups = ext4_get_groups_count(sb);
> int ret;
> int freed = 0;
>
> trace_mark(ext4_mb_discard_preallocations, "dev %s needed %d",
> sb->s_id, needed);
> - for (i = 0; i < EXT4_SB(sb)->s_groups_count && needed > 0; i++) {
> + for (i = 0; i < ngroups && needed > 0; i++) {
> ret = ext4_mb_discard_group_preallocations(sb, i, needed);
> freed += ret;
> needed -= ret;
> diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> index 241a81e..bcdbb6d 100644
> --- a/fs/ext4/super.c
> +++ b/fs/ext4/super.c
> @@ -3539,9 +3539,8 @@ static int ext4_statfs(struct dentry *dentry, struct kstatfs *buf)
> if (test_opt(sb, MINIX_DF)) {
> sbi->s_overhead_last = 0;
> } else if (sbi->s_blocks_last != ext4_blocks_count(es)) {
> - ext4_group_t ngroups = sbi->s_groups_count, i;
> + ext4_group_t i, ngroups = ext4_get_groups_count(sb);
> ext4_fsblk_t overhead = 0;
> - smp_rmb();
>
> /*
> * Compute the overhead (FS structures). This is constant
> --
> 1.6.0.4
>
--
Jan Kara <jack@xxxxxxx>
SUSE Labs, CR
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