fat: remove i_alloc_sem abuse

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.

Note that we can't simply use i_mutex, given that the swapon code
calls ->bmap under it.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>

diff --git a/fs/fat/fat.h b/fs/fat/fat.h
index 8276cc2..a975b41 100644 (file)
--- a/fs/fat/fat.h
+++ b/fs/fat/fat.h
@@ -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;
 };
 

diff --git a/fs/fat/file.c b/fs/fat/file.c
index 7018e1d..a4a3a3c 100644 (file)
--- a/fs/fat/file.c
+++ b/fs/fat/file.c
@@ -429,8 +429,10 @@ int fat_setattr(struct dentry *dentry, struct iattr *attr)
        }
 
        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);

diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index cb8d839..3decce4 100644 (file)
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -224,9 +224,9 @@ static sector_t _fat_bmap(struct address_space *mapping, sector_t block)
        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(struct super_block *sb)
        ei = kmem_cache_alloc(fat_inode_cachep, GFP_NOFS);
        if (!ei)
                return NULL;
+
+       init_rwsem(&ei->truncate_lock);
        return &ei->vfs_inode;
 }