[PATCH 08/12] ext4: hold i_rwsem until AIO completes

Christoph Hellwig
2020-01-14T16:13:18Z

Switch ext4 from the magic i_dio_count scheme to just hold i_rwsem
until the actual I/O has completed to reduce the locking complexity
and avoid nasty bugs due to missing inode_dio_wait calls.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
fs/ext4/extents.c | 12 ------------
fs/ext4/file.c | 21 +++++++++++++--------
fs/ext4/inode.c | 11 -----------
fs/ext4/ioctl.c | 5 -----
fs/ext4/move_extent.c | 4 ----
5 files changed, 13 insertions(+), 40 deletions(-)

diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 0e8708b77da6..b6aa2d249b30 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -4777,9 +4777,6 @@ static long ext4_zero_range(struct file *file, loff_t offset,
if (mode & FALLOC_FL_KEEP_SIZE)
flags |= EXT4_GET_BLOCKS_KEEP_SIZE;

- /* Wait all existing dio workers, newcomers will block on i_mutex */
- inode_dio_wait(inode);
-
/* Preallocate the range including the unaligned edges */
if (partial_begin || partial_end) {
ret = ext4_alloc_file_blocks(file,
@@ -4949,9 +4946,6 @@ long ext4_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
goto out;
}

- /* Wait all existing dio workers, newcomers will block on i_mutex */
- inode_dio_wait(inode);
-
ret = ext4_alloc_file_blocks(file, lblk, max_blocks, new_size, flags);
if (ret)
goto out;
@@ -5525,9 +5519,6 @@ int ext4_collapse_range(struct inode *inode, loff_t offset, loff_t len)
goto out_mutex;
}

- /* Wait for existing dio to complete */
- inode_dio_wait(inode);
-
/*
* Prevent page faults from reinstantiating pages we have released from
* page cache.
@@ -5678,9 +5669,6 @@ int ext4_insert_range(struct inode *inode, loff_t offset, loff_t len)
goto out_mutex;
}

- /* Wait for existing dio to complete */
- inode_dio_wait(inode);
-
/*
* Prevent page faults from reinstantiating pages we have released from
* page cache.
diff --git a/fs/ext4/file.c b/fs/ext4/file.c
index 08b603d0c638..b3410a3ede27 100644
--- a/fs/ext4/file.c
+++ b/fs/ext4/file.c
@@ -74,9 +74,10 @@ static ssize_t ext4_dio_read_iter(struct kiocb *iocb, struct iov_iter *to)
return generic_file_read_iter(iocb, to);
}

- ret = iomap_dio_rw(iocb, to, &ext4_iomap_ops, NULL, 0);
- inode_unlock_shared(inode);
-
+ ret = iomap_dio_rw(iocb, to, &ext4_iomap_ops, NULL,
+ IOMAP_DIO_RWSEM_SHARED);
+ if (ret != -EIOCBQUEUED)
+ inode_unlock_shared(inode);
file_accessed(iocb->ki_filp);
return ret;
}
@@ -405,7 +406,6 @@ static ssize_t ext4_dio_write_iter(struct kiocb *iocb, struct iov_iter *from)
!is_sync_kiocb(iocb) && ext4_unaligned_aio(inode, from, offset)) {
unaligned_aio = true;
dio_flags |= IOMAP_DIO_SYNCHRONOUS;
- inode_dio_wait(inode);
}

/*
@@ -416,7 +416,10 @@ static ssize_t ext4_dio_write_iter(struct kiocb *iocb, struct iov_iter *from)
if (!unaligned_aio && ext4_overwrite_io(inode, offset, count) &&
ext4_should_dioread_nolock(inode)) {
overwrite = true;
+ dio_flags |= IOMAP_DIO_RWSEM_SHARED;
downgrade_write(&inode->i_rwsem);
+ } else {
+ dio_flags |= IOMAP_DIO_RWSEM_EXCL;
}

if (offset + count > EXT4_I(inode)->i_disksize) {
@@ -444,10 +447,12 @@ static ssize_t ext4_dio_write_iter(struct kiocb *iocb, struct iov_iter *from)
ret = ext4_handle_inode_extension(inode, offset, ret, count);

out:
- if (overwrite)
- inode_unlock_shared(inode);
- else
- inode_unlock(inode);
+ if (ret != -EIOCBQUEUED) {
+ if (overwrite)
+ inode_unlock_shared(inode);
+ else
+ inode_unlock(inode);
+ }

if (ret >= 0 && iov_iter_count(from)) {
ssize_t err;
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 629a25d999f0..e2dac0727ab0 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3965,9 +3965,6 @@ int ext4_punch_hole(struct inode *inode, loff_t offset, loff_t length)

}

- /* Wait all existing dio workers, newcomers will block on i_mutex */
- inode_dio_wait(inode);
-
/*
* Prevent page faults from reinstantiating pages we have released from
* page cache.
@@ -5263,11 +5260,6 @@ int ext4_setattr(struct dentry *dentry, struct iattr *attr)
if (error)
goto err_out;
}
- /*
- * Blocks are going to be removed from the inode. Wait
- * for dio in flight.
- */
- inode_dio_wait(inode);
}

down_write(&EXT4_I(inode)->i_mmap_sem);
@@ -5798,9 +5790,6 @@ int ext4_change_inode_journal_flag(struct inode *inode, int val)
if (is_journal_aborted(journal))
return -EROFS;

- /* Wait for all existing dio workers */
- inode_dio_wait(inode);
-
/*
* Before flushing the journal and switching inode's aops, we have
* to flush all dirty data the inode has. There can be outstanding
diff --git a/fs/ext4/ioctl.c b/fs/ext4/ioctl.c
index e8870fff8224..99d21d81074f 100644
--- a/fs/ext4/ioctl.c
+++ b/fs/ext4/ioctl.c
@@ -153,10 +153,6 @@ static long swap_inode_boot_loader(struct super_block *sb,
if (err)
goto err_out;

- /* Wait for all existing dio workers */
- inode_dio_wait(inode);
- inode_dio_wait(inode_bl);
-
truncate_inode_pages(&inode->i_data, 0);
truncate_inode_pages(&inode_bl->i_data, 0);

@@ -364,7 +360,6 @@ static int ext4_ioctl_setflags(struct inode *inode,
*/
if (S_ISREG(inode->i_mode) && !IS_IMMUTABLE(inode) &&
(flags & EXT4_IMMUTABLE_FL)) {
- inode_dio_wait(inode);
err = filemap_write_and_wait(inode->i_mapping);
if (err)
goto flags_out;
diff --git a/fs/ext4/move_extent.c b/fs/ext4/move_extent.c
index 30ce3dc69378..20240808569f 100644
--- a/fs/ext4/move_extent.c
+++ b/fs/ext4/move_extent.c
@@ -602,10 +602,6 @@ ext4_move_extents(struct file *o_filp, struct file *d_filp, __u64 orig_blk,
/* Protect orig and donor inodes against a truncate */
lock_two_nondirectories(orig_inode, donor_inode);

- /* Wait for all existing dio workers */
- inode_dio_wait(orig_inode);
- inode_dio_wait(donor_inode);
-
/* Protect extent tree against block allocations via delalloc */
ext4_double_down_write_data_sem(orig_inode, donor_inode);
/* Check the filesystem environment whether move_extent can be done */
--
2.24.1