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.
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);
--
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