* [PATCH v3] Return bytes transferred for partial direct I/O
@ 2017-09-29 15:50 Goldwyn Rodrigues
2017-10-01 8:22 ` Christoph Hellwig
0 siblings, 1 reply; 2+ messages in thread
From: Goldwyn Rodrigues @ 2017-09-29 15:50 UTC (permalink / raw)
To: linux-fsdevel; +Cc: hch, willy, Goldwyn Rodrigues
In case direct I/O encounters an error midway, it returns the error.
Instead it should be returning the number of bytes transferred so far.
Test case for filesystems (with ENOSPC):
1. Create an almost full filesystem
2. Create a file, say /mnt/lastfile, until the filesystem is full.
3. Direct write() with count > sizeof /mnt/lastfile.
Result: write() returns -ENOSPC. However, file content has data written
in step 3.
Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Changes since v1:
- incorporated iomap and block devices
Changes since v2:
- realized that file size was not increasing when performing a (partial)
direct I/O because end_io function was receiving the error instead of
size in iomap's dio end io. Fixed.
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 93d088ffc05c..1c6640ffb929 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -421,7 +421,7 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
if (!ret)
ret = blk_status_to_errno(dio->bio.bi_status);
- if (likely(!ret))
+ if (likely(dio->size))
ret = dio->size;
bio_put(&dio->bio);
diff --git a/fs/direct-io.c b/fs/direct-io.c
index 5fa2211e49ae..0fc1789498ae 100644
--- a/fs/direct-io.c
+++ b/fs/direct-io.c
@@ -255,8 +255,6 @@ static ssize_t dio_complete(struct dio *dio, ssize_t ret, bool is_async)
ret = dio->page_errors;
if (ret == 0)
ret = dio->io_error;
- if (ret == 0)
- ret = transferred;
if (dio->end_io) {
int err;
@@ -284,7 +282,7 @@ static ssize_t dio_complete(struct dio *dio, ssize_t ret, bool is_async)
}
kmem_cache_free(dio_cache, dio);
- return ret;
+ return transferred ? transferred : ret;
}
static void dio_aio_complete_work(struct work_struct *work)
diff --git a/fs/iomap.c b/fs/iomap.c
index 269b24a01f32..019c4d993300 100644
--- a/fs/iomap.c
+++ b/fs/iomap.c
@@ -714,28 +714,29 @@ static ssize_t iomap_dio_complete(struct iomap_dio *dio)
{
struct kiocb *iocb = dio->iocb;
ssize_t ret;
+ ssize_t transferred = 0;
if (dio->end_io) {
ret = dio->end_io(iocb,
- dio->error ? dio->error : dio->size,
+ dio->size ? dio->size : dio->error,
dio->flags);
} else {
ret = dio->error;
}
- if (likely(!ret)) {
- ret = dio->size;
+ if (likely(dio->size)) {
+ transferred = dio->size;
/* check for short read */
- if (iocb->ki_pos + ret > dio->i_size &&
+ if (iocb->ki_pos + transferred > dio->i_size &&
!(dio->flags & IOMAP_DIO_WRITE))
- ret = dio->i_size - iocb->ki_pos;
- iocb->ki_pos += ret;
+ transferred = dio->i_size - iocb->ki_pos;
+ iocb->ki_pos += transferred;
}
inode_dio_end(file_inode(iocb->ki_filp));
kfree(dio);
- return ret;
+ return transferred ? transferred : ret;
}
static void iomap_dio_complete_work(struct work_struct *work)
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH v3] Return bytes transferred for partial direct I/O
2017-09-29 15:50 [PATCH v3] Return bytes transferred for partial direct I/O Goldwyn Rodrigues
@ 2017-10-01 8:22 ` Christoph Hellwig
0 siblings, 0 replies; 2+ messages in thread
From: Christoph Hellwig @ 2017-10-01 8:22 UTC (permalink / raw)
To: Goldwyn Rodrigues; +Cc: linux-fsdevel, hch, willy, Goldwyn Rodrigues
On Fri, Sep 29, 2017 at 10:50:30AM -0500, Goldwyn Rodrigues wrote:
> In case direct I/O encounters an error midway, it returns the error.
> Instead it should be returning the number of bytes transferred so far.
>
> Test case for filesystems (with ENOSPC):
> 1. Create an almost full filesystem
> 2. Create a file, say /mnt/lastfile, until the filesystem is full.
> 3. Direct write() with count > sizeof /mnt/lastfile.
>
> Result: write() returns -ENOSPC. However, file content has data written
> in step 3.
>
> Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
>
> Changes since v1:
> - incorporated iomap and block devices
>
> Changes since v2:
> - realized that file size was not increasing when performing a (partial)
> direct I/O because end_io function was receiving the error instead of
> size in iomap's dio end io. Fixed.
>
> diff --git a/fs/block_dev.c b/fs/block_dev.c
> index 93d088ffc05c..1c6640ffb929 100644
> --- a/fs/block_dev.c
> +++ b/fs/block_dev.c
> @@ -421,7 +421,7 @@ __blkdev_direct_IO(struct kiocb *iocb, struct iov_iter *iter, int nr_pages)
>
> if (!ret)
> ret = blk_status_to_errno(dio->bio.bi_status);
> - if (likely(!ret))
> + if (likely(dio->size))
> ret = dio->size;
>
> bio_put(&dio->bio);
> diff --git a/fs/direct-io.c b/fs/direct-io.c
> index 5fa2211e49ae..0fc1789498ae 100644
> --- a/fs/direct-io.c
> +++ b/fs/direct-io.c
> @@ -255,8 +255,6 @@ static ssize_t dio_complete(struct dio *dio, ssize_t ret, bool is_async)
> ret = dio->page_errors;
> if (ret == 0)
> ret = dio->io_error;
> - if (ret == 0)
> - ret = transferred;
>
> if (dio->end_io) {
> int err;
> @@ -284,7 +282,7 @@ static ssize_t dio_complete(struct dio *dio, ssize_t ret, bool is_async)
> }
>
> kmem_cache_free(dio_cache, dio);
> - return ret;
> + return transferred ? transferred : ret;
> }
>
> static void dio_aio_complete_work(struct work_struct *work)
> diff --git a/fs/iomap.c b/fs/iomap.c
> index 269b24a01f32..019c4d993300 100644
> --- a/fs/iomap.c
> +++ b/fs/iomap.c
> @@ -714,28 +714,29 @@ static ssize_t iomap_dio_complete(struct iomap_dio *dio)
> {
> struct kiocb *iocb = dio->iocb;
> ssize_t ret;
> + ssize_t transferred = 0;
How about initializing this to dio->size here and then using it
further down everywere you currently use dio->size?
Otherwise looks fine:
Reviewed-by: Christoph Hellwig <hch@lst.de>
^ permalink raw reply [flat|nested] 2+ messages in thread
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2017-09-29 15:50 [PATCH v3] Return bytes transferred for partial direct I/O Goldwyn Rodrigues
2017-10-01 8:22 ` Christoph Hellwig
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