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Message-ID: <2b595b62f6ecd28298a860fcdc5b4941dcafd9eb.camel@kernel.org>
Date: Wed, 16 Nov 2022 06:58:01 -0500
From: Jeff Layton <jlayton@...nel.org>
To: Jingbo Xu <jefflexu@...ux.alibaba.com>, xiang@...nel.org,
chao@...nel.org, linux-erofs@...ts.ozlabs.org,
linux-cachefs@...hat.com, dhowells@...hat.com
Cc: linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v3 1/2] fscache,cachefiles: add prepare_ondemand_read()
callback
On Wed, 2022-11-16 at 18:45 +0800, Jingbo Xu wrote:
> Add prepare_ondemand_read() callback dedicated for the on-demand read
> scenario, so that callers from this scenario can be decoupled from
> netfs_io_subrequest.
>
> The original cachefiles_prepare_read() is now refactored to a generic
> routine accepting a parameter list instead of netfs_io_subrequest.
> There's no logic change, except that some debug info retrieved from
> netfs_io_subrequest is removed from trace_cachefiles_prep_read().
>
> Signed-off-by: Jingbo Xu <jefflexu@...ux.alibaba.com>
> ---
> fs/cachefiles/io.c | 75 ++++++++++++++++++++-----------
> include/linux/netfs.h | 7 +++
> include/trace/events/cachefiles.h | 27 ++++++-----
> 3 files changed, 68 insertions(+), 41 deletions(-)
>
> diff --git a/fs/cachefiles/io.c b/fs/cachefiles/io.c
> index 000a28f46e59..3eeafef21c4e 100644
> --- a/fs/cachefiles/io.c
> +++ b/fs/cachefiles/io.c
> @@ -385,38 +385,35 @@ static int cachefiles_write(struct netfs_cache_resources *cres,
> term_func, term_func_priv);
> }
>
> -/*
> - * Prepare a read operation, shortening it to a cached/uncached
> - * boundary as appropriate.
> - */
> -static enum netfs_io_source cachefiles_prepare_read(struct netfs_io_subrequest *subreq,
> - loff_t i_size)
> +static enum netfs_io_source cachefiles_do_prepare_read(struct netfs_cache_resources *cres,
> + loff_t *_start, size_t *_len,
> + unsigned long *_flags, loff_t i_size)
_start is never changed, so it should be passed by value instead of by
pointer. I'd also reverse the position of the arguments for _flags and
i_size. Otherwise, the CPU/compiler have to shuffle things around more
in cachefiles_prepare_ondemand_read before they call this.
> {
> enum cachefiles_prepare_read_trace why;
> - struct netfs_io_request *rreq = subreq->rreq;
> - struct netfs_cache_resources *cres = &rreq->cache_resources;
> - struct cachefiles_object *object;
> + struct cachefiles_object *object = NULL;
> struct cachefiles_cache *cache;
> struct fscache_cookie *cookie = fscache_cres_cookie(cres);
> const struct cred *saved_cred;
> struct file *file = cachefiles_cres_file(cres);
> enum netfs_io_source ret = NETFS_DOWNLOAD_FROM_SERVER;
> + loff_t start = *_start;
> + size_t len = *_len;
> loff_t off, to;
> ino_t ino = file ? file_inode(file)->i_ino : 0;
> int rc;
>
> - _enter("%zx @%llx/%llx", subreq->len, subreq->start, i_size);
> + _enter("%zx @%llx/%llx", len, start, i_size);
>
> - if (subreq->start >= i_size) {
> + if (start >= i_size) {
> ret = NETFS_FILL_WITH_ZEROES;
> why = cachefiles_trace_read_after_eof;
> goto out_no_object;
> }
>
> if (test_bit(FSCACHE_COOKIE_NO_DATA_TO_READ, &cookie->flags)) {
> - __set_bit(NETFS_SREQ_COPY_TO_CACHE, &subreq->flags);
> + __set_bit(NETFS_SREQ_COPY_TO_CACHE, _flags);
> why = cachefiles_trace_read_no_data;
> - if (!test_bit(NETFS_SREQ_ONDEMAND, &subreq->flags))
> + if (!test_bit(NETFS_SREQ_ONDEMAND, _flags))
> goto out_no_object;
> }
>
> @@ -437,7 +434,7 @@ static enum netfs_io_source cachefiles_prepare_read(struct netfs_io_subrequest *
> retry:
> off = cachefiles_inject_read_error();
> if (off == 0)
> - off = vfs_llseek(file, subreq->start, SEEK_DATA);
> + off = vfs_llseek(file, start, SEEK_DATA);
> if (off < 0 && off >= (loff_t)-MAX_ERRNO) {
> if (off == (loff_t)-ENXIO) {
> why = cachefiles_trace_read_seek_nxio;
> @@ -449,21 +446,22 @@ static enum netfs_io_source cachefiles_prepare_read(struct netfs_io_subrequest *
> goto out;
> }
>
> - if (off >= subreq->start + subreq->len) {
> + if (off >= start + len) {
> why = cachefiles_trace_read_found_hole;
> goto download_and_store;
> }
>
> - if (off > subreq->start) {
> + if (off > start) {
> off = round_up(off, cache->bsize);
> - subreq->len = off - subreq->start;
> + len = off - start;
> + *_len = len;
> why = cachefiles_trace_read_found_part;
> goto download_and_store;
> }
>
> to = cachefiles_inject_read_error();
> if (to == 0)
> - to = vfs_llseek(file, subreq->start, SEEK_HOLE);
> + to = vfs_llseek(file, start, SEEK_HOLE);
> if (to < 0 && to >= (loff_t)-MAX_ERRNO) {
> trace_cachefiles_io_error(object, file_inode(file), to,
> cachefiles_trace_seek_error);
> @@ -471,12 +469,13 @@ static enum netfs_io_source cachefiles_prepare_read(struct netfs_io_subrequest *
> goto out;
> }
>
> - if (to < subreq->start + subreq->len) {
> - if (subreq->start + subreq->len >= i_size)
> + if (to < start + len) {
> + if (start + len >= i_size)
> to = round_up(to, cache->bsize);
> else
> to = round_down(to, cache->bsize);
> - subreq->len = to - subreq->start;
> + len = to - start;
> + *_len = len;
> }
>
> why = cachefiles_trace_read_have_data;
> @@ -484,12 +483,11 @@ static enum netfs_io_source cachefiles_prepare_read(struct netfs_io_subrequest *
> goto out;
>
> download_and_store:
> - __set_bit(NETFS_SREQ_COPY_TO_CACHE, &subreq->flags);
> - if (test_bit(NETFS_SREQ_ONDEMAND, &subreq->flags)) {
> - rc = cachefiles_ondemand_read(object, subreq->start,
> - subreq->len);
> + __set_bit(NETFS_SREQ_COPY_TO_CACHE, _flags);
> + if (test_bit(NETFS_SREQ_ONDEMAND, _flags)) {
> + rc = cachefiles_ondemand_read(object, start, len);
> if (!rc) {
> - __clear_bit(NETFS_SREQ_ONDEMAND, &subreq->flags);
> + __clear_bit(NETFS_SREQ_ONDEMAND, _flags);
> goto retry;
> }
> ret = NETFS_INVALID_READ;
> @@ -497,10 +495,32 @@ static enum netfs_io_source cachefiles_prepare_read(struct netfs_io_subrequest *
> out:
> cachefiles_end_secure(cache, saved_cred);
> out_no_object:
> - trace_cachefiles_prep_read(subreq, ret, why, ino);
> + trace_cachefiles_prep_read(object, start, len, *_flags, ret, why, ino);
> return ret;
> }
>
> +/*
> + * Prepare a read operation, shortening it to a cached/uncached
> + * boundary as appropriate.
> + */
> +static enum netfs_io_source cachefiles_prepare_read(struct netfs_io_subrequest *subreq,
> + loff_t i_size)
> +{
> + return cachefiles_do_prepare_read(&subreq->rreq->cache_resources,
> + &subreq->start, &subreq->len, &subreq->flags, i_size);
> +}
> +
> +/*
> + * Prepare an on-demand read operation, shortening it to a cached/uncached
> + * boundary as appropriate.
> + */
> +static enum netfs_io_source cachefiles_prepare_ondemand_read(struct netfs_cache_resources *cres,
> + loff_t start, size_t *_len, loff_t i_size)
> +{
> + unsigned long flags = 1 << NETFS_SREQ_ONDEMAND;
> + return cachefiles_do_prepare_read(cres, &start, _len, &flags, i_size);
> +}
> +
> /*
> * Prepare for a write to occur.
> */
> @@ -621,6 +641,7 @@ static const struct netfs_cache_ops cachefiles_netfs_cache_ops = {
> .write = cachefiles_write,
> .prepare_read = cachefiles_prepare_read,
> .prepare_write = cachefiles_prepare_write,
> + .prepare_ondemand_read = cachefiles_prepare_ondemand_read,
> .query_occupancy = cachefiles_query_occupancy,
> };
>
> diff --git a/include/linux/netfs.h b/include/linux/netfs.h
> index f2402ddeafbf..d82071c37133 100644
> --- a/include/linux/netfs.h
> +++ b/include/linux/netfs.h
> @@ -267,6 +267,13 @@ struct netfs_cache_ops {
> loff_t *_start, size_t *_len, loff_t i_size,
> bool no_space_allocated_yet);
>
> + /* Prepare an on-demand read operation, shortening it to a cached/uncached
> + * boundary as appropriate.
> + */
> + enum netfs_io_source (*prepare_ondemand_read)(struct netfs_cache_resources *cres,
> + loff_t start, size_t *_len,
> + loff_t i_size);
> +
> /* Query the occupancy of the cache in a region, returning where the
> * next chunk of data starts and how long it is.
> */
> diff --git a/include/trace/events/cachefiles.h b/include/trace/events/cachefiles.h
> index d8d4d73fe7b6..171c0d7f0bb7 100644
> --- a/include/trace/events/cachefiles.h
> +++ b/include/trace/events/cachefiles.h
> @@ -428,44 +428,43 @@ TRACE_EVENT(cachefiles_vol_coherency,
> );
>
> TRACE_EVENT(cachefiles_prep_read,
> - TP_PROTO(struct netfs_io_subrequest *sreq,
> + TP_PROTO(struct cachefiles_object *obj,
> + loff_t start,
> + size_t len,
> + unsigned short flags,
> enum netfs_io_source source,
> enum cachefiles_prepare_read_trace why,
> ino_t cache_inode),
>
> - TP_ARGS(sreq, source, why, cache_inode),
> + TP_ARGS(obj, start, len, flags, source, why, cache_inode),
>
> TP_STRUCT__entry(
> - __field(unsigned int, rreq )
> - __field(unsigned short, index )
> + __field(unsigned int, obj )
> __field(unsigned short, flags )
> __field(enum netfs_io_source, source )
> __field(enum cachefiles_prepare_read_trace, why )
> __field(size_t, len )
> __field(loff_t, start )
> - __field(unsigned int, netfs_inode )
> __field(unsigned int, cache_inode )
> ),
>
> TP_fast_assign(
> - __entry->rreq = sreq->rreq->debug_id;
> - __entry->index = sreq->debug_index;
> - __entry->flags = sreq->flags;
> + __entry->obj = obj ? obj->debug_id : 0;
> + __entry->flags = flags;
> __entry->source = source;
> __entry->why = why;
> - __entry->len = sreq->len;
> - __entry->start = sreq->start;
> - __entry->netfs_inode = sreq->rreq->inode->i_ino;
> + __entry->len = len;
> + __entry->start = start;
> __entry->cache_inode = cache_inode;
> ),
>
> - TP_printk("R=%08x[%u] %s %s f=%02x s=%llx %zx ni=%x B=%x",
> - __entry->rreq, __entry->index,
> + TP_printk("o=%08x %s %s f=%02x s=%llx %zx B=%x",
> + __entry->obj,
> __print_symbolic(__entry->source, netfs_sreq_sources),
> __print_symbolic(__entry->why, cachefiles_prepare_read_traces),
> __entry->flags,
> __entry->start, __entry->len,
> - __entry->netfs_inode, __entry->cache_inode)
> + __entry->cache_inode)
> );
>
> TRACE_EVENT(cachefiles_read,
The rest looks pretty reasonable though.
--
Jeff Layton <jlayton@...nel.org>
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