Commit 8318ba79 authored by Josef Bacik's avatar Josef Bacik Committed by David Sterba
Browse files

btrfs: add a i_mmap_lock to our inode 



We need to be able to exclude page_mkwrite from happening concurrently
with certain operations.  To facilitate this, add a i_mmap_lock to our
inode, down_read() it in our mkwrite, and add a new ILOCK flag to
indicate that we want to take the i_mmap_lock as well.  I used pahole to
check the size of the btrfs_inode, the sizes are as follows

no lockdep:
before: 1120 (3 per 4k page)
after: 1160 (3 per 4k page)

lockdep:
before: 2072 (1 per 4k page)
after: 2224 (1 per 4k page)

We're slightly larger but it doesn't change how many objects we can fit
per page.

Reviewed-by: default avatarFilipe Manana <fdmanana@suse.com>
Signed-off-by: default avatarJosef Bacik <josef@toxicpanda.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent 5e295768

fs/btrfs/btrfs_inode.h

+1 −0
Original line number Diff line number Diff line
@@ -220,6 +220,7 @@ struct btrfs_inode { 
	/* Hook into fs_info->delayed_iputs */

	struct list_head delayed_iput;



	struct rw_semaphore i_mmap_lock;

	struct inode vfs_inode;

};

fs/btrfs/ctree.h

+1 −0
Original line number Diff line number Diff line
@@ -3178,6 +3178,7 @@ extern const struct iomap_dio_ops btrfs_dio_ops; 
/* Inode locking type flags, by default the exclusive lock is taken */

#define BTRFS_ILOCK_SHARED	(1U << 0)

#define BTRFS_ILOCK_TRY 	(1U << 1)

#define BTRFS_ILOCK_MMAP	(1U << 2)



int btrfs_inode_lock(struct inode *inode, unsigned int ilock_flags);

void btrfs_inode_unlock(struct inode *inode, unsigned int ilock_flags);

fs/btrfs/inode.c

+10 −0
Original line number Diff line number Diff line
@@ -102,6 +102,7 @@ static void __endio_write_update_ordered(struct btrfs_inode *inode, 
 * BTRFS_ILOCK_SHARED - acquire a shared lock on the inode

 * BTRFS_ILOCK_TRY - try to acquire the lock, if fails on first attempt

 *		     return -EAGAIN

 * BTRFS_ILOCK_MMAP - acquire a write lock on the i_mmap_lock

 */

int btrfs_inode_lock(struct inode *inode, unsigned int ilock_flags)

{
@@ -122,6 +123,8 @@ int btrfs_inode_lock(struct inode *inode, unsigned int ilock_flags) 
		}

		inode_lock(inode);

	}

	if (ilock_flags & BTRFS_ILOCK_MMAP)

		down_write(&BTRFS_I(inode)->i_mmap_lock);

	return 0;

}
@@ -133,6 +136,8 @@ int btrfs_inode_lock(struct inode *inode, unsigned int ilock_flags) 
 */

void btrfs_inode_unlock(struct inode *inode, unsigned int ilock_flags)

{

	if (ilock_flags & BTRFS_ILOCK_MMAP)

		up_write(&BTRFS_I(inode)->i_mmap_lock);

	if (ilock_flags & BTRFS_ILOCK_SHARED)

		inode_unlock_shared(inode);

	else
@@ -8540,6 +8545,7 @@ vm_fault_t btrfs_page_mkwrite(struct vm_fault *vmf) 


	ret = VM_FAULT_NOPAGE; /* make the VM retry the fault */

again:

	down_read(&BTRFS_I(inode)->i_mmap_lock);

	lock_page(page);

	size = i_size_read(inode);
@@ -8568,6 +8574,7 @@ vm_fault_t btrfs_page_mkwrite(struct vm_fault *vmf) 
		unlock_extent_cached(io_tree, page_start, page_end,

				     &cached_state);

		unlock_page(page);

		up_read(&BTRFS_I(inode)->i_mmap_lock);

		btrfs_start_ordered_extent(ordered, 1);

		btrfs_put_ordered_extent(ordered);

		goto again;
@@ -8625,6 +8632,7 @@ vm_fault_t btrfs_page_mkwrite(struct vm_fault *vmf) 
	BTRFS_I(inode)->last_log_commit = BTRFS_I(inode)->root->last_log_commit;



	unlock_extent_cached(io_tree, page_start, page_end, &cached_state);

	up_read(&BTRFS_I(inode)->i_mmap_lock);



	btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE);

	sb_end_pagefault(inode->i_sb);
@@ -8633,6 +8641,7 @@ vm_fault_t btrfs_page_mkwrite(struct vm_fault *vmf) 


out_unlock:

	unlock_page(page);

	up_read(&BTRFS_I(inode)->i_mmap_lock);

out:

	btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE);

	btrfs_delalloc_release_space(BTRFS_I(inode), data_reserved, page_start,
@@ -8884,6 +8893,7 @@ struct inode *btrfs_alloc_inode(struct super_block *sb) 
	INIT_LIST_HEAD(&ei->delalloc_inodes);

	INIT_LIST_HEAD(&ei->delayed_iput);

	RB_CLEAR_NODE(&ei->rb_node);

	init_rwsem(&ei->i_mmap_lock);



	return inode;

}