If we release the lockdep write protection token before calling into
->write_iter and thus never access the file pointer after an -EIOCBQUEUED
return from ->write_iter or ->read_iter we don't need this extra
reference.
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
fs/aio.c | 25 ++++++++++++++++---------
1 file changed, 16 insertions(+), 9 deletions(-)
diff --git a/fs/aio.c b/fs/aio.c
index 18507743757a..e5866e2fc331 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1515,16 +1515,19 @@ static ssize_t aio_write(struct kiocb *req, struct iocb *iocb, bool vectored,
return ret;
ret = rw_verify_area(WRITE, file, &req->ki_pos, iov_iter_count(&iter));
if (!ret) {
- req->ki_flags |= IOCB_WRITE;
- file_start_write(file);
- ret = aio_ret(req, call_write_iter(file, req, &iter));
/*
- * We release freeze protection in aio_complete(). Fool lockdep
- * by telling it the lock got released so that it doesn't
- * complain about held lock when we return to userspace.
+ * Open-code file_start_write here to grab freeze protection,
+ * which will be released by another thread in aio_complete().
+ * Fool lockdep by telling it the lock got released so that it
+ * doesn't complain about the held lock when we return to
+ * userspace.
*/
- if (S_ISREG(file_inode(file)->i_mode))
+ if (S_ISREG(file_inode(file)->i_mode)) {
+ __sb_start_write(file_inode(file)->i_sb, SB_FREEZE_WRITE, true);
__sb_writers_release(file_inode(file)->i_sb, SB_FREEZE_WRITE);
+ }
+ req->ki_flags |= IOCB_WRITE;
+ ret = aio_ret(req, call_write_iter(file, req, &iter));
}
kfree(iovec);
return ret;
@@ -1599,7 +1602,6 @@ static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
req->ki_user_iocb = user_iocb;
req->ki_user_data = iocb->aio_data;
- get_file(file);
switch (iocb->aio_lio_opcode) {
case IOCB_CMD_PREAD:
ret = aio_read(&req->common, iocb, false, compat);
@@ -1618,8 +1620,13 @@ static int io_submit_one(struct kioctx *ctx, struct iocb __user *user_iocb,
ret = -EINVAL;
break;
}
- fput(file);
+ /*
+ * If ret is -EIOCBQUEUED, ownership of the file reference acquired
+ * above passed to the file system, which at this point might have
+ * dropped the reference, so we must be careful to not reference it
+ * once we have called into the file system.
+ */
if (ret && ret != -EIOCBQUEUED)
goto out_put_req;
return 0;
--
2.17.0
--
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