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SubjectRe: [Patch v2 02/15] CIFS: Add support for direct pages in rdata
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On 5/30/2018 3:47 PM, Long Li wrote:
> From: Long Li <longli@microsoft.com>
>
> Add a function to allocate rdata without allocating pages for data
> transfer. This gives the caller an option to pass a number of pages
> that point to the data buffer.
>
> rdata is still reponsible for free those pages after it's done.

"Caller" is still responsible? Or is the rdata somehow freeing itself
via another mechanism?

>
> Signed-off-by: Long Li <longli@microsoft.com>
> ---
> fs/cifs/cifsglob.h | 2 +-
> fs/cifs/file.c | 23 ++++++++++++++++++++---
> 2 files changed, 21 insertions(+), 4 deletions(-)
>
> diff --git a/fs/cifs/cifsglob.h b/fs/cifs/cifsglob.h
> index 8d16c3e..56864a87 100644
> --- a/fs/cifs/cifsglob.h
> +++ b/fs/cifs/cifsglob.h
> @@ -1179,7 +1179,7 @@ struct cifs_readdata {
> unsigned int tailsz;
> unsigned int credits;
> unsigned int nr_pages;
> - struct page *pages[];
> + struct page **pages;

Technically speaking, these are syntactically equivalent. It may not
be worth changing this historic definition.

Tom.


> };
>
> struct cifs_writedata;
> diff --git a/fs/cifs/file.c b/fs/cifs/file.c
> index 23fd430..1c98293 100644
> --- a/fs/cifs/file.c
> +++ b/fs/cifs/file.c
> @@ -2880,13 +2880,13 @@ cifs_strict_writev(struct kiocb *iocb, struct iov_iter *from)
> }
>
> static struct cifs_readdata *
> -cifs_readdata_alloc(unsigned int nr_pages, work_func_t complete)
> +cifs_readdata_direct_alloc(struct page **pages, work_func_t complete)
> {
> struct cifs_readdata *rdata;
>
> - rdata = kzalloc(sizeof(*rdata) + (sizeof(struct page *) * nr_pages),
> - GFP_KERNEL);
> + rdata = kzalloc(sizeof(*rdata), GFP_KERNEL);
> if (rdata != NULL) {
> + rdata->pages = pages;
> kref_init(&rdata->refcount);
> INIT_LIST_HEAD(&rdata->list);
> init_completion(&rdata->done);
> @@ -2896,6 +2896,22 @@ cifs_readdata_alloc(unsigned int nr_pages, work_func_t complete)
> return rdata;
> }
>
> +static struct cifs_readdata *
> +cifs_readdata_alloc(unsigned int nr_pages, work_func_t complete)
> +{
> + struct page **pages =
> + kzalloc(sizeof(struct page *) * nr_pages, GFP_KERNEL);
> + struct cifs_readdata *ret = NULL;
> +
> + if (pages) {
> + ret = cifs_readdata_direct_alloc(pages, complete);
> + if (!ret)
> + kfree(pages);
> + }
> +
> + return ret;
> +}
> +
> void
> cifs_readdata_release(struct kref *refcount)
> {
> @@ -2910,6 +2926,7 @@ cifs_readdata_release(struct kref *refcount)
> if (rdata->cfile)
> cifsFileInfo_put(rdata->cfile);
>
> + kvfree(rdata->pages);
> kfree(rdata);
> }
>
>

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