[PATCH v2 1/2] fscache,cachefiles: add prepare_ondemand_read() callback

Jingbo Xu
2022-11-08T02:57:20Z

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@linux.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)
{
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,
--
2.19.1.6.gb485710b