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iomap: Allow filesystem to call iomap_dio_complete without i_rwsem

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This is to avoid the deadlock caused in btrfs because of O_DIRECT |
O_DSYNC.

Filesystems such as btrfs require i_rwsem while performing sync on a
file. iomap_dio_rw() is called under i_rw_sem. This leads to a
deadlock because of:

iomap_dio_complete()
  generic_write_sync()
    btrfs_sync_file()

Separate out iomap_dio_complete() from iomap_dio_rw(), so filesystems
can call iomap_dio_complete() after unlocking i_rwsem.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>
This commit is contained in:
Christoph Hellwig 2020-09-28 08:51:08 -07:00 committed by Darrick J. Wong
parent 4595a298d5
commit c3d4ed1abe
2 changed files with 31 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

35
fs/iomap/direct-io.c
View File

@ -76,7 +76,7 @@ static void iomap_dio_submit_bio(struct iomap_dio *dio, struct iomap *iomap,
dio->submit.cookie = submit_bio(bio);
}
static ssize_t iomap_dio_complete(struct iomap_dio *dio)
ssize_t iomap_dio_complete(struct iomap_dio *dio)
{
const struct iomap_dio_ops *dops = dio->dops;
struct kiocb *iocb = dio->iocb;
@ -130,6 +130,7 @@ static ssize_t iomap_dio_complete(struct iomap_dio *dio)
return ret;
}
EXPORT_SYMBOL_GPL(iomap_dio_complete);
static void iomap_dio_complete_work(struct work_struct *work)
{
@ -416,8 +417,8 @@ iomap_dio_actor(struct inode *inode, loff_t pos, loff_t length,
* Returns -ENOTBLK In case of a page invalidation invalidation failure for
* writes. The callers needs to fall back to buffered I/O in this case.
*/
ssize_t
iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
struct iomap_dio *
__iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
const struct iomap_ops *ops, const struct iomap_dio_ops *dops,
bool wait_for_completion)
{
@ -431,14 +432,14 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
struct iomap_dio *dio;
if (!count)
return 0;
return NULL;
if (WARN_ON(is_sync_kiocb(iocb) && !wait_for_completion))
return -EIO;
return ERR_PTR(-EIO);
dio = kmalloc(sizeof(*dio), GFP_KERNEL);
if (!dio)
return -ENOMEM;
return ERR_PTR(-ENOMEM);
dio->iocb = iocb;
atomic_set(&dio->ref, 1);
@ -568,7 +569,7 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
dio->wait_for_completion = wait_for_completion;
if (!atomic_dec_and_test(&dio->ref)) {
if (!wait_for_completion)
return -EIOCBQUEUED;
return ERR_PTR(-EIOCBQUEUED);
for (;;) {
set_current_state(TASK_UNINTERRUPTIBLE);
@ -584,10 +585,26 @@ iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
__set_current_state(TASK_RUNNING);
}
return iomap_dio_complete(dio);
return dio;
out_free_dio:
kfree(dio);
return ret;
if (ret)
return ERR_PTR(ret);
return NULL;
}
EXPORT_SYMBOL_GPL(__iomap_dio_rw);
ssize_t
iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
const struct iomap_ops *ops, const struct iomap_dio_ops *dops,
bool wait_for_completion)
{
struct iomap_dio *dio;
dio = __iomap_dio_rw(iocb, iter, ops, dops, wait_for_completion);
if (IS_ERR_OR_NULL(dio))
return PTR_ERR_OR_ZERO(dio);
return iomap_dio_complete(dio);
}
EXPORT_SYMBOL_GPL(iomap_dio_rw);

5
include/linux/iomap.h
View File

@ -13,6 +13,7 @@
struct address_space;
struct fiemap_extent_info;
struct inode;
struct iomap_dio;
struct iomap_writepage_ctx;
struct iov_iter;
struct kiocb;
@ -258,6 +259,10 @@ struct iomap_dio_ops {
ssize_t iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
const struct iomap_ops *ops, const struct iomap_dio_ops *dops,
bool wait_for_completion);
struct iomap_dio *__iomap_dio_rw(struct kiocb *iocb, struct iov_iter *iter,
const struct iomap_ops *ops, const struct iomap_dio_ops *dops,
bool wait_for_completion);
ssize_t iomap_dio_complete(struct iomap_dio *dio);
int iomap_dio_iopoll(struct kiocb *kiocb, bool spin);
#ifdef CONFIG_SWAP