2015-04-09 09:32:44

by Dmitry Monakhov

[permalink] [raw]
Subject: Re: [PATCH 2/7] Add support for per-file stream ID

Jens Axboe <[email protected]> writes:

One small question.
You states that all IDs are equals but can we reserve some IDs
for internal kernel purposes. For example very short lived data (files
opened with O_TEMP) and so on.

Also small nitpicking see below.
> Writing on flash devices can be much more efficient, if we can
> inform the device what kind of data can be grouped together. If
> the device is able to group data together with similar lifetimes,
> then it can be more efficient in garbage collection. This, in turn,
> leads to lower write amplification, which is a win on both device
> wear and performance.
>
> Add a new fadvise hint, POSIX_FADV_STREAMID, which sets the file
> and inode streamid. The file streamid is used if we have the file
> available at the time of the write (O_DIRECT), we use the inode
> streamid if not (buffered writeback). The fadvise hint uses the
> 'offset' field to specify a stream ID.
>
> Signed-off-by: Jens Axboe <[email protected]>
> ---
> fs/inode.c | 1 +
> fs/open.c | 1 +
> include/linux/fs.h | 23 +++++++++++++++++++++++
> include/uapi/linux/fadvise.h | 2 ++
> mm/fadvise.c | 17 +++++++++++++++++
> 5 files changed, 44 insertions(+)
>
> diff --git a/fs/inode.c b/fs/inode.c
> index f00b16f45507..41885322ba64 100644
> --- a/fs/inode.c
> +++ b/fs/inode.c
> @@ -149,6 +149,7 @@ int inode_init_always(struct super_block *sb, struct inode *inode)
> inode->i_blocks = 0;
> inode->i_bytes = 0;
> inode->i_generation = 0;
> + inode->i_streamid = 0;
> inode->i_pipe = NULL;
> inode->i_bdev = NULL;
> inode->i_cdev = NULL;
> diff --git a/fs/open.c b/fs/open.c
> index 33f9cbf2610b..4a9b2be1a674 100644
> --- a/fs/open.c
> +++ b/fs/open.c
> @@ -743,6 +743,7 @@ static int do_dentry_open(struct file *f,
> f->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);
>
> file_ra_state_init(&f->f_ra, f->f_mapping->host->i_mapping);
> + f->f_streamid = 0;
>
> return 0;
>
> diff --git a/include/linux/fs.h b/include/linux/fs.h
> index b4d71b5e1ff2..43dde70c1d0d 100644
> --- a/include/linux/fs.h
> +++ b/include/linux/fs.h
> @@ -631,6 +631,7 @@ struct inode {
> };
>
> __u32 i_generation;
> + unsigned int i_streamid;
>
> #ifdef CONFIG_FSNOTIFY
> __u32 i_fsnotify_mask; /* all events this inode cares about */
> @@ -640,6 +641,14 @@ struct inode {
> void *i_private; /* fs or device private pointer */
> };
>
> +static inline unsigned int inode_streamid(struct inode *inode)
> +{
> + if (inode)
> + return inode->i_streamid;
> +
> + return 0;
> +}
> +
> static inline int inode_unhashed(struct inode *inode)
> {
> return hlist_unhashed(&inode->i_hash);
> @@ -820,6 +829,8 @@ struct file {
> const struct cred *f_cred;
> struct file_ra_state f_ra;
>
> + unsigned int f_streamid;
> +
> u64 f_version;
> #ifdef CONFIG_SECURITY
> void *f_security;
> @@ -842,6 +853,18 @@ struct file_handle {
> unsigned char f_handle[0];
> };
>
> +/*
> + * If the file doesn't have a stream ID set, return the inode stream ID
> + * in case that has been set.
> + */
> +static inline unsigned int file_streamid(struct file *f)
> +{
> + if (f->f_streamid)
> + return f->f_streamid;
> +
> + return inode_streamid(f->f_inode);
> +}
> +
> static inline struct file *get_file(struct file *f)
> {
> atomic_long_inc(&f->f_count);
> diff --git a/include/uapi/linux/fadvise.h b/include/uapi/linux/fadvise.h
> index e8e747139b9a..3dc8a1ff1422 100644
> --- a/include/uapi/linux/fadvise.h
> +++ b/include/uapi/linux/fadvise.h
> @@ -18,4 +18,6 @@
> #define POSIX_FADV_NOREUSE 5 /* Data will be accessed once. */
> #endif
>
> +#define POSIX_FADV_STREAMID 8 /* associate stream ID with file */
> +
> #endif /* FADVISE_H_INCLUDED */
> diff --git a/mm/fadvise.c b/mm/fadvise.c
> index 4a3907cf79f8..b111a8899fb7 100644
> --- a/mm/fadvise.c
> +++ b/mm/fadvise.c
> @@ -60,6 +60,7 @@ SYSCALL_DEFINE4(fadvise64_64, int, fd, loff_t, offset, loff_t, len, int, advice)
> case POSIX_FADV_WILLNEED:
> case POSIX_FADV_NOREUSE:
> case POSIX_FADV_DONTNEED:
> + case POSIX_FADV_STREAMID:
> /* no bad return value, but ignore advice */
> break;
> default:
> @@ -144,6 +145,22 @@ SYSCALL_DEFINE4(fadvise64_64, int, fd, loff_t, offset, loff_t, len, int, advice)
> }
> }
> break;
> + case POSIX_FADV_STREAMID:
> + /*
> + * streamid is stored in offset... we don't limit or check
> + * if the device supports streams, or if it does, if the
> + * stream nr is within the limits. 1 is the lowest valid
> + * stream id, 0 is "don't care/know".
> + */
> + if (offset != (unsigned int) offset)
> + ret = EINVAL;
Shuld be negative ret = -EINVAL;
> + else {
> + f.file->f_streamid = offset;
> + spin_lock(&inode->i_lock);
> + inode->i_streamid = offset;
> + spin_unlock(&inode->i_lock);
> + }
> + break;
> default:
> ret = -EINVAL;
> }
> --
> 1.9.1
>
> --
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2015-04-09 16:28:13

by Jens Axboe

[permalink] [raw]
Subject: Re: [PATCH 2/7] Add support for per-file stream ID

On 04/09/2015 03:30 AM, Dmitry Monakhov wrote:
> Jens Axboe <[email protected]> writes:
>
> One small question.
> You states that all IDs are equals but can we reserve some IDs
> for internal kernel purposes. For example very short lived data (files
> opened with O_TEMP) and so on.

Yes, we probably should end up reserving some IDs for specific internal
things. O_TEMP to a specific stream would make sense. Journal writes
too, for instance.

I just preferred not wiring any of that up, as it then gets closer to
being a policy decision. I'm mainly interested in getting this exposed
to userspace, and seeing how the hw side develops since that will
influence how we actually use this (number of streams, any actions
required to manage streams, etc).

>> + case POSIX_FADV_STREAMID:
>> + /*
>> + * streamid is stored in offset... we don't limit or check
>> + * if the device supports streams, or if it does, if the
>> + * stream nr is within the limits. 1 is the lowest valid
>> + * stream id, 0 is "don't care/know".
>> + */
>> + if (offset != (unsigned int) offset)
>> + ret = EINVAL;
> Shuld be negative ret = -EINVAL;

Indeed it should, thanks!

--
Jens Axboe