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btrfs: add a i_mmap_lock to our inode

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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: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Josef Bacik <josef@toxicpanda.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Josef Bacik 2021-02-10 17:14:33 -05:00 committed by David Sterba
parent 5e295768a0
commit 8318ba79ee
3 changed files with 12 additions and 0 deletions
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1
fs/btrfs/btrfs_inode.h
View File

@ -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;
};

1
fs/btrfs/ctree.h
View File

@ -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);

10
fs/btrfs/inode.c
View File

@ -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 @@ again:
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 @@ again:
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 @@ again:
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;
}