On Tue, 2014-02-18 at 14:06 -0800, Andrew Morton wrote:
> On Mon, 17 Feb 2014 14:20:47 +0200 Sougata Santra <sougata@xxxxxxxxxx> wrote:
>
> >
> > Concurrent access to alloc_blocks in hfsplus_inode_info is
> > protected by extents_lock mutex. This patch fixes two
> > instances where alloc_blocks modification was not protected
> > with this lock. This fixes possible allocation bitmap
> > corruption in race conditions while extending and truncating
> > files.
> >
> > ...
> >
> > --- a/fs/hfsplus/extents.c
> > +++ b/fs/hfsplus/extents.c
> > @@ -498,11 +498,13 @@ int hfsplus_file_extend(struct inode *inode)
> > goto insert_extent;
> > }
> > out:
> > - mutex_unlock(&hip->extents_lock);
> > if (!res) {
> > hip->alloc_blocks += len;
> > + mutex_unlock(&hip->extents_lock);
> > hfsplus_mark_inode_dirty(inode, HFSPLUS_I_ALLOC_DIRTY);
> > + return 0;
> > }
> > + mutex_unlock(&hip->extents_lock);
> > return res;
> >
>
> This looks OK.
>
> > @@ -592,9 +594,9 @@ void hfsplus_file_truncate(struct inode *inode)
> > hfs_brec_remove(&fd);
> > }
> > hfs_find_exit(&fd);
> > - mutex_unlock(&hip->extents_lock);
> >
> > hip->alloc_blocks = blk_cnt;
> > + mutex_unlock(&hip->extents_lock);
> > out:
> > hip->phys_size = inode->i_size;
> > hip->fs_blocks = (inode->i_size + sb->s_blocksize - 1) >>
>
> But this does not. To provide locking for
> hfsplus_inode_info.alloc_blocks, we must take the lock *before* taking
> a local copy of ->alloc_blocks.
>
> Please review:
>
> --- a/fs/hfsplus/extents.c~hfsplus-fix-concurrent-acess-of-alloc_blocks-fix
> +++ a/fs/hfsplus/extents.c
> @@ -556,11 +556,13 @@ void hfsplus_file_truncate(struct inode
>
> blk_cnt = (inode->i_size + HFSPLUS_SB(sb)->alloc_blksz - 1) >>
> HFSPLUS_SB(sb)->alloc_blksz_shift;
> +
> + mutex_lock(&hip->extents_lock);
> +
> alloc_cnt = hip->alloc_blocks;
> if (blk_cnt == alloc_cnt)
> - goto out;
> + goto out_unlock;
>
> - mutex_lock(&hip->extents_lock);
> res = hfs_find_init(HFSPLUS_SB(sb)->ext_tree, &fd);
> if (res) {
> mutex_unlock(&hip->extents_lock);
> @@ -594,6 +596,7 @@ void hfsplus_file_truncate(struct inode
> hfs_find_exit(&fd);
>
> hip->alloc_blocks = blk_cnt;
> +out_unlock:
> mutex_unlock(&hip->extents_lock);
> out:
> hip->phys_size = inode->i_size;
> _
>
This is good, Missed it. Thank you.
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