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Date: Wed, 19 Feb 2014 11:53:18 +0200 From: sougata santra <sougata@...era.com> To: Andrew Morton <akpm@...ux-foundation.org> CC: Christoph Hellwig <hch@....de>, <linux-fsdevel@...r.kernel.org>, <linux-kernel@...r.kernel.org>, Vyacheslav Dubeyko <slava@...eyko.com>, Joe Perches <joe@...ches.com>, Alexey Khoroshilov <khoroshilov@...ras.ru> Subject: Re: [PATCH] hfsplus: fix concurrent acess of alloc_blocks On 02/19/2014 12:06 AM, Andrew Morton wrote: > On Mon, 17 Feb 2014 14:20:47 +0200 Sougata Santra <sougata@...era.com> 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: We can also remove this label ? > hip->phys_size = inode->i_size; > _ > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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