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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>
This commit is contained in:
Christoph Hellwig 2011-06-24 14:29:40 -04:00 committed by Al Viro
parent 8c5dc70aae
commit 5826869158
3 changed files with 7 additions and 2 deletions
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1
fs/fat/fat.h
View File

@ -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;
};

2
fs/fat/file.c
View File

@ -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);

6
fs/fat/inode.c
View File

@ -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;
}