Commit 29504ff3 authored by Daniel McNeil's avatar Daniel McNeil Committed by Linus Torvalds

[PATCH] Direct IO async short read fix

The direct I/O code is mapping the read request to the file system block.  If
the file size was not on a block boundary, the result would show the the read
reading past EOF.  This was only happening for the AIO case.  The non-AIO case
truncates the result to match file size (in direct_io_worker).  This patch
does the same thing for the AIO case, it truncates the result to match the
file size if the read reads past EOF.

When I/O completes the result can be truncated to match the file size
without using i_size_read(), thus the aio result now matches the number of
bytes read to the end of file.
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 1f08ad02
......@@ -66,6 +66,7 @@ struct dio {
struct bio *bio; /* bio under assembly */
struct inode *inode;
int rw;
loff_t i_size; /* i_size when submitted */
int lock_type; /* doesn't change */
unsigned blkbits; /* doesn't change */
unsigned blkfactor; /* When we're using an alignment which
......@@ -230,17 +231,29 @@ static void finished_one_bio(struct dio *dio)
spin_lock_irqsave(&dio->bio_lock, flags);
if (dio->bio_count == 1) {
if (dio->is_async) {
ssize_t transferred;
loff_t offset;
* Last reference to the dio is going away.
* Drop spinlock and complete the DIO.
spin_unlock_irqrestore(&dio->bio_lock, flags);
dio_complete(dio, dio->block_in_file << dio->blkbits,
/* Check for short read case */
transferred = dio->result;
offset = dio->iocb->ki_pos;
if ((dio->rw == READ) &&
((offset + transferred) > dio->i_size))
transferred = dio->i_size - offset;
dio_complete(dio, offset, transferred);
/* Complete AIO later if falling back to buffered i/o */
if (dio->result == dio->size ||
((dio->rw == READ) && dio->result)) {
aio_complete(dio->iocb, dio->result, 0);
aio_complete(dio->iocb, transferred, 0);
} else {
......@@ -951,6 +964,7 @@ direct_io_worker(int rw, struct kiocb *iocb, struct inode *inode,
dio->page_errors = 0;
dio->result = 0;
dio->iocb = iocb;
dio->i_size = i_size_read(inode);
* BIO completion state.
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