Add a new rw_semaphore to protect page_mkwrite 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/ext4/inode.c
===================================================================
--- linux-2.6.orig/fs/ext4/inode.c 2011-06-20 14:25:33.779248128 +0200
+++ linux-2.6/fs/ext4/inode.c 2011-06-20 14:27:53.025907745 +0200
@@ -5357,6 +5357,7 @@ int ext4_setattr(struct dentry *dentry,
if (attr->ia_size > sbi->s_bitmap_maxbytes)
return -EFBIG;
}
+ down_write(&(EXT4_I(inode)->truncate_lock));
}
if (S_ISREG(inode->i_mode) &&
@@ -5405,6 +5406,9 @@ int ext4_setattr(struct dentry *dentry,
ext4_truncate(inode);
}
+ if (attr->ia_valid & ATTR_SIZE)
+ up_write(&(EXT4_I(inode)->truncate_lock));
+
if (!rc) {
setattr_copy(inode, attr);
mark_inode_dirty(inode);
@@ -5850,10 +5854,10 @@ int ext4_page_mkwrite(struct vm_area_str
struct address_space *mapping = inode->i_mapping;
/*
- * Get i_alloc_sem to stop truncates messing with the inode. We cannot
- * get i_mutex because we are already holding mmap_sem.
+ * Get truncate_lock to stop truncates messing with the inode. We
+ * cannot get i_mutex because we are already holding mmap_sem.
*/
- down_read(&inode->i_alloc_sem);
+ down_read(&(EXT4_I(inode)->truncate_lock));
size = i_size_read(inode);
if (page->mapping != mapping || size <= page_offset(page)
|| !PageUptodate(page)) {
@@ -5865,7 +5869,7 @@ int ext4_page_mkwrite(struct vm_area_str
lock_page(page);
wait_on_page_writeback(page);
if (PageMappedToDisk(page)) {
- up_read(&inode->i_alloc_sem);
+ up_read(&(EXT4_I(inode)->truncate_lock));
return VM_FAULT_LOCKED;
}
@@ -5883,7 +5887,7 @@ int ext4_page_mkwrite(struct vm_area_str
if (page_has_buffers(page)) {
if (!walk_page_buffers(NULL, page_buffers(page), 0, len, NULL,
ext4_bh_unmapped)) {
- up_read(&inode->i_alloc_sem);
+ up_read(&(EXT4_I(inode)->truncate_lock));
return VM_FAULT_LOCKED;
}
}
@@ -5912,11 +5916,11 @@ int ext4_page_mkwrite(struct vm_area_str
*/
lock_page(page);
wait_on_page_writeback(page);
- up_read(&inode->i_alloc_sem);
+ up_read(&(EXT4_I(inode)->truncate_lock));
return VM_FAULT_LOCKED;
out_unlock:
if (ret)
ret = VM_FAULT_SIGBUS;
- up_read(&inode->i_alloc_sem);
+ up_read(&(EXT4_I(inode)->truncate_lock));
return ret;
}
Index: linux-2.6/fs/ext4/super.c
===================================================================
--- linux-2.6.orig/fs/ext4/super.c 2011-06-20 14:25:33.795914793 +0200
+++ linux-2.6/fs/ext4/super.c 2011-06-20 14:27:06.269243443 +0200
@@ -871,6 +871,7 @@ static struct inode *ext4_alloc_inode(st
ei->i_datasync_tid = 0;
atomic_set(&ei->i_ioend_count, 0);
atomic_set(&ei->i_aiodio_unwritten, 0);
+ init_rwsem(&ei->truncate_lock);
return &ei->vfs_inode;
}
Index: linux-2.6/fs/ext4/ext4.h
===================================================================
--- linux-2.6.orig/fs/ext4/ext4.h 2011-06-20 14:25:33.752581461 +0200
+++ linux-2.6/fs/ext4/ext4.h 2011-06-20 14:27:06.272576777 +0200
@@ -844,6 +844,9 @@ struct ext4_inode_info {
/* on-disk additional length */
__u16 i_extra_isize;
+ /* protect page_mkwrite against truncates */
+ struct rw_semaphore truncate_lock;
+
#ifdef CONFIG_QUOTA
/* quota space reservation, managed internally by quota code */
qsize_t i_reserved_quota;
--
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