From 0568b409c74f7a125d92a09a3f386785700ef688 Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Mon, 1 May 2006 19:50:48 +0200 Subject: [PATCH] splice: fix bugs in pipe_to_file() Found by Oleg Nesterov , fixed by me. - Only allow full pages to go to the page cache. - Check page != buf->page instead of using PIPE_BUF_FLAG_STOLEN. - Remember to clear 'stolen' if add_to_page_cache() fails. And as a cleanup on that: - Make the bottom fall-through logic a little less convoluted. Also make the steal path hold an extra reference to the page, so we don't have to differentiate between stolen and non-stolen at the end. Signed-off-by: Jens Axboe --- include/linux/pipe_fs_i.h | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) (limited to 'include') diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h index 0008d4bd4059..3130977fc6ab 100644 --- a/include/linux/pipe_fs_i.h +++ b/include/linux/pipe_fs_i.h @@ -5,8 +5,7 @@ #define PIPE_BUFFERS (16) -#define PIPE_BUF_FLAG_STOLEN 0x01 -#define PIPE_BUF_FLAG_LRU 0x02 +#define PIPE_BUF_FLAG_LRU 0x01 struct pipe_buffer { struct page *page; -- cgit v1.2.3 From f84d751994441292593523c7069ed147176f6cab Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Mon, 1 May 2006 19:59:03 +0200 Subject: [PATCH] pipe: introduce ->pin() buffer operation The ->map() function is really expensive on highmem machines right now, since it has to use the slower kmap() instead of kmap_atomic(). Splice rarely needs to access the virtual address of a page, so it's a waste of time doing it. Introduce ->pin() to take over the responsibility of making sure the page data is valid. ->map() is then reduced to just kmap(). That way we can also share a most of the pipe buffer ops between pipe.c and splice.c Signed-off-by: Jens Axboe --- include/linux/pipe_fs_i.h | 21 ++++++++++++++++++++- 1 file changed, 20 insertions(+), 1 deletion(-) (limited to 'include') diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h index 3130977fc6ab..b8aae1fc5185 100644 --- a/include/linux/pipe_fs_i.h +++ b/include/linux/pipe_fs_i.h @@ -14,10 +14,23 @@ struct pipe_buffer { unsigned int flags; }; +/* + * Note on the nesting of these functions: + * + * ->pin() + * ->steal() + * ... + * ->map() + * ... + * ->unmap() + * + * That is, ->map() must be called on a pinned buffer, same goes for ->steal(). + */ struct pipe_buf_operations { int can_merge; - void * (*map)(struct file *, struct pipe_inode_info *, struct pipe_buffer *); + void * (*map)(struct pipe_inode_info *, struct pipe_buffer *); void (*unmap)(struct pipe_inode_info *, struct pipe_buffer *); + int (*pin)(struct pipe_inode_info *, struct pipe_buffer *); void (*release)(struct pipe_inode_info *, struct pipe_buffer *); int (*steal)(struct pipe_inode_info *, struct pipe_buffer *); void (*get)(struct pipe_inode_info *, struct pipe_buffer *); @@ -50,6 +63,12 @@ struct pipe_inode_info * alloc_pipe_info(struct inode * inode); void free_pipe_info(struct inode * inode); void __free_pipe_info(struct pipe_inode_info *); +/* Generic pipe buffer ops functions */ +void *generic_pipe_buf_map(struct pipe_inode_info *, struct pipe_buffer *); +void generic_pipe_buf_unmap(struct pipe_inode_info *, struct pipe_buffer *); +void generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *); +int generic_pipe_buf_pin(struct pipe_inode_info *, struct pipe_buffer *); + /* * splice is tied to pipes as a transport (at least for now), so we'll just * add the splice flags here. -- cgit v1.2.3 From f6762b7ad8edd6abc802542ce845d3bc8adcb92f Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Mon, 1 May 2006 20:02:05 +0200 Subject: [PATCH] pipe: enable atomic copying of pipe data to/from user space The pipe ->map() method uses kmap() to virtually map the pages, which is both slow and has known scalability issues on SMP. This patch enables atomic copying of pipe pages, by pre-faulting data and using kmap_atomic() instead. lmbench bw_pipe and lat_pipe measurements agree this is a Good Thing. Here are results from that on a UP machine with highmem (1.5GiB of RAM), running first a UP kernel, SMP kernel, and SMP kernel patched. Vanilla-UP: Pipe bandwidth: 1622.28 MB/sec Pipe bandwidth: 1610.59 MB/sec Pipe bandwidth: 1608.30 MB/sec Pipe latency: 7.3275 microseconds Pipe latency: 7.2995 microseconds Pipe latency: 7.3097 microseconds Vanilla-SMP: Pipe bandwidth: 1382.19 MB/sec Pipe bandwidth: 1317.27 MB/sec Pipe bandwidth: 1355.61 MB/sec Pipe latency: 9.6402 microseconds Pipe latency: 9.6696 microseconds Pipe latency: 9.6153 microseconds Patched-SMP: Pipe bandwidth: 1578.70 MB/sec Pipe bandwidth: 1579.95 MB/sec Pipe bandwidth: 1578.63 MB/sec Pipe latency: 9.1654 microseconds Pipe latency: 9.2266 microseconds Pipe latency: 9.1527 microseconds Signed-off-by: Jens Axboe --- include/linux/pipe_fs_i.h | 11 ++++++----- 1 file changed, 6 insertions(+), 5 deletions(-) (limited to 'include') diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h index b8aae1fc5185..4c054491e38e 100644 --- a/include/linux/pipe_fs_i.h +++ b/include/linux/pipe_fs_i.h @@ -5,7 +5,8 @@ #define PIPE_BUFFERS (16) -#define PIPE_BUF_FLAG_LRU 0x01 +#define PIPE_BUF_FLAG_LRU 0x01 /* page is on the LRU */ +#define PIPE_BUF_FLAG_ATOMIC 0x02 /* was atomically mapped */ struct pipe_buffer { struct page *page; @@ -28,8 +29,8 @@ struct pipe_buffer { */ struct pipe_buf_operations { int can_merge; - void * (*map)(struct pipe_inode_info *, struct pipe_buffer *); - void (*unmap)(struct pipe_inode_info *, struct pipe_buffer *); + void * (*map)(struct pipe_inode_info *, struct pipe_buffer *, int); + void (*unmap)(struct pipe_inode_info *, struct pipe_buffer *, void *); int (*pin)(struct pipe_inode_info *, struct pipe_buffer *); void (*release)(struct pipe_inode_info *, struct pipe_buffer *); int (*steal)(struct pipe_inode_info *, struct pipe_buffer *); @@ -64,8 +65,8 @@ void free_pipe_info(struct inode * inode); void __free_pipe_info(struct pipe_inode_info *); /* Generic pipe buffer ops functions */ -void *generic_pipe_buf_map(struct pipe_inode_info *, struct pipe_buffer *); -void generic_pipe_buf_unmap(struct pipe_inode_info *, struct pipe_buffer *); +void *generic_pipe_buf_map(struct pipe_inode_info *, struct pipe_buffer *, int); +void generic_pipe_buf_unmap(struct pipe_inode_info *, struct pipe_buffer *, void *); void generic_pipe_buf_get(struct pipe_inode_info *, struct pipe_buffer *); int generic_pipe_buf_pin(struct pipe_inode_info *, struct pipe_buffer *); -- cgit v1.2.3 From 7afa6fd037e51e95d322990cb127bb2b1217251a Mon Sep 17 00:00:00 2001 From: Jens Axboe Date: Mon, 1 May 2006 20:02:33 +0200 Subject: [PATCH] vmsplice: allow user to pass in gift pages If SPLICE_F_GIFT is set, the user is basically giving this pages away to the kernel. That means we can steal them for eg page cache uses instead of copying it. The data must be properly page aligned and also a multiple of the page size in length. Signed-off-by: Jens Axboe --- include/linux/pipe_fs_i.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include') diff --git a/include/linux/pipe_fs_i.h b/include/linux/pipe_fs_i.h index 4c054491e38e..df4d3fa7d3dc 100644 --- a/include/linux/pipe_fs_i.h +++ b/include/linux/pipe_fs_i.h @@ -7,6 +7,7 @@ #define PIPE_BUF_FLAG_LRU 0x01 /* page is on the LRU */ #define PIPE_BUF_FLAG_ATOMIC 0x02 /* was atomically mapped */ +#define PIPE_BUF_FLAG_GIFT 0x04 /* page is a gift */ struct pipe_buffer { struct page *page; @@ -79,6 +80,7 @@ int generic_pipe_buf_pin(struct pipe_inode_info *, struct pipe_buffer *); /* we may still block on the fd we splice */ /* from/to, of course */ #define SPLICE_F_MORE (0x04) /* expect more data */ +#define SPLICE_F_GIFT (0x08) /* pages passed in are a gift */ /* * Passed to the actors -- cgit v1.2.3