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aio: remove the extra get_file/fput pair in io_submit_one 

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@lst.de>
hifive-unleashed-5.1
Christoph Hellwig 2018-04-06 09:28:17 +02:00
parent 75321b50a3
commit 92ce472856
1 changed files with 16 additions and 9 deletions
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25
fs/aio.c
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@ -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;