From: OGAWA Hirofumi Subject: Re: [PATCH 1/8] far: remove i_alloc_sem abuse Date: Wed, 22 Jun 2011 00:57:43 +0900 Message-ID: <87fwn3mb2g.fsf@devron.myhome.or.jp> References: <20110620201533.847236272@bombadil.infradead.org> <20110620202030.577464178@bombadil.infradead.org> Mime-Version: 1.0 Content-Type: text/plain Cc: viro@zeniv.linux.org.uk, tglx@linutronix.de, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-btrfs@vger.kernel.org, mfasheh@suse.com, jlbec@evilplan.org To: Christoph Hellwig Return-path: In-Reply-To: <20110620202030.577464178@bombadil.infradead.org> (Christoph Hellwig's message of "Mon, 20 Jun 2011 16:15:34 -0400") Sender: linux-btrfs-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org Christoph Hellwig writes: > Add a new rw_semaphore to protect bmap against truncate. Previous > i_alloc_sem was abused for this, but it's going away in this series. In FAT case, ->i_mutex was better. But, last time I saw, shmfs was using ->i_mutex to call ->bmap. So, this was chosen instead. I'm not checking current version yet though, if shmfs had change, we can use ->i_mutex. BTW, this patch looks good to me. Thanks. > Signed-off-by: Christoph Hellwig > > Index: linux-2.6/fs/fat/inode.c > =================================================================== > --- linux-2.6.orig/fs/fat/inode.c 2011-06-20 21:28:19.707963855 +0200 > +++ linux-2.6/fs/fat/inode.c 2011-06-20 21:29:25.031293882 +0200 > @@ -224,9 +224,9 @@ static sector_t _fat_bmap(struct address > sector_t blocknr; > > /* fat_get_cluster() assumes the requested blocknr isn't truncated. */ > - down_read(&mapping->host->i_alloc_sem); > + down_read(&MSDOS_I(mapping->host)->truncate_lock); > blocknr = generic_block_bmap(mapping, block, fat_get_block); > - up_read(&mapping->host->i_alloc_sem); > + up_read(&MSDOS_I(mapping->host)->truncate_lock); > > return blocknr; > } > @@ -510,6 +510,8 @@ static struct inode *fat_alloc_inode(str > ei = kmem_cache_alloc(fat_inode_cachep, GFP_NOFS); > if (!ei) > return NULL; > + > + init_rwsem(&ei->truncate_lock); > return &ei->vfs_inode; > } > > Index: linux-2.6/fs/fat/fat.h > =================================================================== > --- linux-2.6.orig/fs/fat/fat.h 2011-06-20 21:28:19.724630522 +0200 > +++ linux-2.6/fs/fat/fat.h 2011-06-20 21:29:25.034627215 +0200 > @@ -109,6 +109,7 @@ struct msdos_inode_info { > int i_attrs; /* unused attribute bits */ > loff_t i_pos; /* on-disk position of directory entry or 0 */ > struct hlist_node i_fat_hash; /* hash by i_location */ > + struct rw_semaphore truncate_lock; /* protect bmap against truncate */ > struct inode vfs_inode; > }; > > Index: linux-2.6/fs/fat/file.c > =================================================================== > --- linux-2.6.orig/fs/fat/file.c 2011-06-20 21:28:19.744630521 +0200 > +++ linux-2.6/fs/fat/file.c 2011-06-20 21:29:54.501292390 +0200 > @@ -429,8 +429,10 @@ int fat_setattr(struct dentry *dentry, s > } > > if (attr->ia_valid & ATTR_SIZE) { > + down_write(&MSDOS_I(inode)->truncate_lock); > truncate_setsize(inode, attr->ia_size); > fat_truncate_blocks(inode, attr->ia_size); > + up_write(&MSDOS_I(inode)->truncate_lock); > } > > setattr_copy(inode, attr); > -- OGAWA Hirofumi