Christoph Hellwig <hch@xxxxxxxxxxxxx> 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 <hch@xxxxxx>
>
> 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 <hirofumi@xxxxxxxxxxxxxxxxxx>
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