v3:
- rebase to v6.1-rc5, while the xas_retry() checking in patch 2 has
been extracted out as a separate fix [1]
[1] commit 37020bbb71d9 ("erofs: fix missing xas_retry() in fscache mode")
(https://github.com/torvalds/linux/commit/37020bbb71d9)
v2:
- patch 1: the generic routine, i.e. cachefiles_do_prepare_read() now
accepts a parameter list instead of netfs_io_subrequest, and thus some
debug info retrieved from netfs_io_subrequest is removed from
trace_cachefiles_prep_read().
- patch 2: add xas_retry() checking in erofs_fscache_req_complete()
[Rationale]
===========
Fscache has been landed as a generic caching management framework in
the Linux kernel for decades. It aims to manage cache data availability
or fetch data if needed. Currently it's mainly used for network fses,
but in principle the main caching subsystem can be used more widely.
We do really like fscache framework and we believe it'd be better to
reuse such framework if possible instead of duplicating other
alternatives for better maintenance and testing. Therefore for our
container image use cases, we applied the existing fscache to implement
on-demand read for erofs in the past months. For more details, also see
[1].
In short, here each erofs filesystem is composed of multiple blobs (or
devices). Each blob corresponds to one fscache cookie to strictly
follow on-disk format and implement the image downloading in a
deterministic manner, which means it has a unique checksum and is signed
by vendors.
Data of each erofs inode can be scattered among multiple blobs (cookie)
since erofs supports chunk-level deduplication. In this case, each
erofs inode can correspond to multiple cookies, and there's a logical to
physical offset mapping between the logical offset in erofs inode and
the physical offset in the backing file.
As described above, per-cookie netfs model can not be used here
directly. Instead, we'd like to propose/decouple a simple set of raw
fscache APIs, to access cache for all fses to use. We believe it's
useful since it's like the relationship between raw bio and iomap, both
of which are useful for local fses. fscache_read() seems a reasonable
candidate and is enough for such use case.
In addition, the on-demand read feature relies on .prepare_read() to
reuse the hole detecting logic as much as possible. However, after
fscache/netfs rework, libnetfs is preferred to access fscache, making
.prepare_read() closely coupled with libnetfs, or more precisely,
netfs_io_subrequest.
[What We Do]
============
As we discussed previously, we propose a new interface, i,e,
.prepare_ondemand_read() dedicated for the on-demand read scenarios,
which is independent on netfs_io_subrequest. The netfs will still use
the original .prepare_read() as usual.
Jingbo Xu (2):
fscache,cachefiles: add prepare_ondemand_read() callback
erofs: switch to prepare_ondemand_read() in fscache mode
fs/cachefiles/io.c | 75 +++++----
fs/erofs/fscache.c | 259 +++++++++++-------------------
include/linux/netfs.h | 7 +
include/trace/events/cachefiles.h | 27 ++--
4 files changed, 160 insertions(+), 208 deletions(-)
--
2.19.1.6.gb485710b
Switch to prepare_ondemand_read() interface and a self-contained request
completion to get rid of netfs_io_[request|subrequest].
The whole request will still be split into slices (subrequest) according
to the cache state of the backing file. As long as one of the
subrequests fails, the whole request will be marked as failed.
Signed-off-by: Jingbo Xu <[email protected]>
---
fs/erofs/fscache.c | 259 ++++++++++++++++-----------------------------
1 file changed, 92 insertions(+), 167 deletions(-)
diff --git a/fs/erofs/fscache.c b/fs/erofs/fscache.c
index af5ed6b9c54d..b82d5180300a 100644
--- a/fs/erofs/fscache.c
+++ b/fs/erofs/fscache.c
@@ -11,257 +11,178 @@ static DEFINE_MUTEX(erofs_domain_cookies_lock);
static LIST_HEAD(erofs_domain_list);
static struct vfsmount *erofs_pseudo_mnt;
-static struct netfs_io_request *erofs_fscache_alloc_request(struct address_space *mapping,
+struct erofs_fscache_request {
+ struct netfs_cache_resources cache_resources;
+ struct address_space *mapping; /* The mapping being accessed */
+ loff_t start; /* Start position */
+ size_t len; /* Length of the request */
+ size_t submitted; /* Length of submitted */
+ short error; /* 0 or error that occurred */
+ refcount_t ref;
+};
+
+static struct erofs_fscache_request *erofs_fscache_req_alloc(struct address_space *mapping,
loff_t start, size_t len)
{
- struct netfs_io_request *rreq;
+ struct erofs_fscache_request *req;
- rreq = kzalloc(sizeof(struct netfs_io_request), GFP_KERNEL);
- if (!rreq)
+ req = kzalloc(sizeof(struct erofs_fscache_request), GFP_KERNEL);
+ if (!req)
return ERR_PTR(-ENOMEM);
- rreq->start = start;
- rreq->len = len;
- rreq->mapping = mapping;
- rreq->inode = mapping->host;
- INIT_LIST_HEAD(&rreq->subrequests);
- refcount_set(&rreq->ref, 1);
- return rreq;
-}
-
-static void erofs_fscache_put_request(struct netfs_io_request *rreq)
-{
- if (!refcount_dec_and_test(&rreq->ref))
- return;
- if (rreq->cache_resources.ops)
- rreq->cache_resources.ops->end_operation(&rreq->cache_resources);
- kfree(rreq);
-}
-
-static void erofs_fscache_put_subrequest(struct netfs_io_subrequest *subreq)
-{
- if (!refcount_dec_and_test(&subreq->ref))
- return;
- erofs_fscache_put_request(subreq->rreq);
- kfree(subreq);
-}
+ req->mapping = mapping;
+ req->start = start;
+ req->len = len;
+ refcount_set(&req->ref, 1);
-static void erofs_fscache_clear_subrequests(struct netfs_io_request *rreq)
-{
- struct netfs_io_subrequest *subreq;
-
- while (!list_empty(&rreq->subrequests)) {
- subreq = list_first_entry(&rreq->subrequests,
- struct netfs_io_subrequest, rreq_link);
- list_del(&subreq->rreq_link);
- erofs_fscache_put_subrequest(subreq);
- }
+ return req;
}
-static void erofs_fscache_rreq_unlock_folios(struct netfs_io_request *rreq)
+static void erofs_fscache_req_complete(struct erofs_fscache_request *req)
{
- struct netfs_io_subrequest *subreq;
struct folio *folio;
- unsigned int iopos = 0;
- pgoff_t start_page = rreq->start / PAGE_SIZE;
- pgoff_t last_page = ((rreq->start + rreq->len) / PAGE_SIZE) - 1;
- bool subreq_failed = false;
+ bool failed = req->error;
+ pgoff_t start_page = req->start / PAGE_SIZE;
+ pgoff_t last_page = ((req->start + req->len) / PAGE_SIZE) - 1;
- XA_STATE(xas, &rreq->mapping->i_pages, start_page);
-
- subreq = list_first_entry(&rreq->subrequests,
- struct netfs_io_subrequest, rreq_link);
- subreq_failed = (subreq->error < 0);
+ XA_STATE(xas, &req->mapping->i_pages, start_page);
rcu_read_lock();
xas_for_each(&xas, folio, last_page) {
- unsigned int pgpos, pgend;
- bool pg_failed = false;
-
if (xas_retry(&xas, folio))
continue;
-
- pgpos = (folio_index(folio) - start_page) * PAGE_SIZE;
- pgend = pgpos + folio_size(folio);
-
- for (;;) {
- if (!subreq) {
- pg_failed = true;
- break;
- }
-
- pg_failed |= subreq_failed;
- if (pgend < iopos + subreq->len)
- break;
-
- iopos += subreq->len;
- if (!list_is_last(&subreq->rreq_link,
- &rreq->subrequests)) {
- subreq = list_next_entry(subreq, rreq_link);
- subreq_failed = (subreq->error < 0);
- } else {
- subreq = NULL;
- subreq_failed = false;
- }
- if (pgend == iopos)
- break;
- }
-
- if (!pg_failed)
+ if (!failed)
folio_mark_uptodate(folio);
-
folio_unlock(folio);
}
rcu_read_unlock();
+
+ if (req->cache_resources.ops)
+ req->cache_resources.ops->end_operation(&req->cache_resources);
+
+ kfree(req);
}
-static void erofs_fscache_rreq_complete(struct netfs_io_request *rreq)
+static void erofs_fscache_req_put(struct erofs_fscache_request *req)
{
- erofs_fscache_rreq_unlock_folios(rreq);
- erofs_fscache_clear_subrequests(rreq);
- erofs_fscache_put_request(rreq);
+ if (refcount_dec_and_test(&req->ref))
+ erofs_fscache_req_complete(req);
}
-static void erofc_fscache_subreq_complete(void *priv,
+static void erofs_fscache_subreq_complete(void *priv,
ssize_t transferred_or_error, bool was_async)
{
- struct netfs_io_subrequest *subreq = priv;
- struct netfs_io_request *rreq = subreq->rreq;
+ struct erofs_fscache_request *req = priv;
if (IS_ERR_VALUE(transferred_or_error))
- subreq->error = transferred_or_error;
-
- if (atomic_dec_and_test(&rreq->nr_outstanding))
- erofs_fscache_rreq_complete(rreq);
-
- erofs_fscache_put_subrequest(subreq);
+ req->error = transferred_or_error;
+ erofs_fscache_req_put(req);
}
/*
- * Read data from fscache and fill the read data into page cache described by
- * @rreq, which shall be both aligned with PAGE_SIZE. @pstart describes
- * the start physical address in the cache file.
+ * Read data from fscache (cookie, pstart, len), and fill the read data into
+ * page cache described by (req->mapping, lstart, len). @pstart describeis the
+ * start physical address in the cache file.
*/
static int erofs_fscache_read_folios_async(struct fscache_cookie *cookie,
- struct netfs_io_request *rreq, loff_t pstart)
+ struct erofs_fscache_request *req, loff_t pstart, size_t len)
{
enum netfs_io_source source;
- struct super_block *sb = rreq->mapping->host->i_sb;
- struct netfs_io_subrequest *subreq;
- struct netfs_cache_resources *cres = &rreq->cache_resources;
+ struct super_block *sb = req->mapping->host->i_sb;
+ struct netfs_cache_resources *cres = &req->cache_resources;
struct iov_iter iter;
- loff_t start = rreq->start;
- size_t len = rreq->len;
+ loff_t lstart = req->start + req->submitted;
size_t done = 0;
int ret;
- atomic_set(&rreq->nr_outstanding, 1);
+ DBG_BUGON(len > req->len - req->submitted);
ret = fscache_begin_read_operation(cres, cookie);
if (ret)
- goto out;
+ return ret;
while (done < len) {
- subreq = kzalloc(sizeof(struct netfs_io_subrequest),
- GFP_KERNEL);
- if (subreq) {
- INIT_LIST_HEAD(&subreq->rreq_link);
- refcount_set(&subreq->ref, 2);
- subreq->rreq = rreq;
- refcount_inc(&rreq->ref);
- } else {
- ret = -ENOMEM;
- goto out;
- }
-
- subreq->start = pstart + done;
- subreq->len = len - done;
- subreq->flags = 1 << NETFS_SREQ_ONDEMAND;
+ loff_t sstart = pstart + done;
+ size_t slen = len - done;
- list_add_tail(&subreq->rreq_link, &rreq->subrequests);
-
- source = cres->ops->prepare_read(subreq, LLONG_MAX);
- if (WARN_ON(subreq->len == 0))
+ source = cres->ops->prepare_ondemand_read(cres, sstart, &slen, LLONG_MAX);
+ if (WARN_ON(slen == 0))
source = NETFS_INVALID_READ;
if (source != NETFS_READ_FROM_CACHE) {
- erofs_err(sb, "failed to fscache prepare_read (source %d)",
- source);
- ret = -EIO;
- subreq->error = ret;
- erofs_fscache_put_subrequest(subreq);
- goto out;
+ erofs_err(sb, "failed to fscache prepare_read (source %d)", source);
+ return -EIO;
}
- atomic_inc(&rreq->nr_outstanding);
+ refcount_inc(&req->ref);
+ iov_iter_xarray(&iter, READ, &req->mapping->i_pages,
+ lstart + done, slen);
- iov_iter_xarray(&iter, READ, &rreq->mapping->i_pages,
- start + done, subreq->len);
-
- ret = fscache_read(cres, subreq->start, &iter,
- NETFS_READ_HOLE_FAIL,
- erofc_fscache_subreq_complete, subreq);
+ ret = fscache_read(cres, sstart, &iter, NETFS_READ_HOLE_FAIL,
+ erofs_fscache_subreq_complete, req);
if (ret == -EIOCBQUEUED)
ret = 0;
if (ret) {
erofs_err(sb, "failed to fscache_read (ret %d)", ret);
- goto out;
+ return ret;
}
- done += subreq->len;
+ done += slen;
}
-out:
- if (atomic_dec_and_test(&rreq->nr_outstanding))
- erofs_fscache_rreq_complete(rreq);
-
- return ret;
+ DBG_BUGON(done != len);
+ req->submitted += len;
+ return 0;
}
static int erofs_fscache_meta_read_folio(struct file *data, struct folio *folio)
{
int ret;
struct super_block *sb = folio_mapping(folio)->host->i_sb;
- struct netfs_io_request *rreq;
+ struct erofs_fscache_request *req;
struct erofs_map_dev mdev = {
.m_deviceid = 0,
.m_pa = folio_pos(folio),
};
ret = erofs_map_dev(sb, &mdev);
- if (ret)
- goto out;
+ if (ret) {
+ folio_unlock(folio);
+ return ret;
+ }
- rreq = erofs_fscache_alloc_request(folio_mapping(folio),
+ req = erofs_fscache_req_alloc(folio_mapping(folio),
folio_pos(folio), folio_size(folio));
- if (IS_ERR(rreq)) {
- ret = PTR_ERR(rreq);
- goto out;
+ if (IS_ERR(req)) {
+ folio_unlock(folio);
+ return PTR_ERR(req);
}
- return erofs_fscache_read_folios_async(mdev.m_fscache->cookie,
- rreq, mdev.m_pa);
-out:
- folio_unlock(folio);
+ ret = erofs_fscache_read_folios_async(mdev.m_fscache->cookie,
+ req, mdev.m_pa, folio_size(folio));
+ if (ret)
+ req->error = ret;
+
+ erofs_fscache_req_put(req);
return ret;
}
/*
* Read into page cache in the range described by (@pos, @len).
*
- * On return, the caller is responsible for page unlocking if the output @unlock
- * is true, or the callee will take this responsibility through netfs_io_request
- * interface.
+ * On return, if the output @unlock is true, the caller is responsible for page
+ * unlocking; otherwise the callee will take this responsibility through request
+ * completion.
*
* The return value is the number of bytes successfully handled, or negative
* error code on failure. The only exception is that, the length of the range
- * instead of the error code is returned on failure after netfs_io_request is
- * allocated, so that .readahead() could advance rac accordingly.
+ * instead of the error code is returned on failure after request is allocated,
+ * so that .readahead() could advance rac accordingly.
*/
static int erofs_fscache_data_read(struct address_space *mapping,
loff_t pos, size_t len, bool *unlock)
{
struct inode *inode = mapping->host;
struct super_block *sb = inode->i_sb;
- struct netfs_io_request *rreq;
+ struct erofs_fscache_request *req;
struct erofs_map_blocks map;
struct erofs_map_dev mdev;
struct iov_iter iter;
@@ -318,13 +239,17 @@ static int erofs_fscache_data_read(struct address_space *mapping,
if (ret)
return ret;
- rreq = erofs_fscache_alloc_request(mapping, pos, count);
- if (IS_ERR(rreq))
- return PTR_ERR(rreq);
+ req = erofs_fscache_req_alloc(mapping, pos, count);
+ if (IS_ERR(req))
+ return PTR_ERR(req);
*unlock = false;
- erofs_fscache_read_folios_async(mdev.m_fscache->cookie,
- rreq, mdev.m_pa + (pos - map.m_la));
+ ret = erofs_fscache_read_folios_async(mdev.m_fscache->cookie,
+ req, mdev.m_pa + (pos - map.m_la), count);
+ if (ret)
+ req->error = ret;
+
+ erofs_fscache_req_put(req);
return count;
}
--
2.19.1.6.gb485710b
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 <[email protected]>
---
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
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 <[email protected]>
> ---
> 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 <[email protected]>
Hi Jeff,
Thanks for the comment!
On 11/16/22 7:58 PM, Jeff Layton wrote:
>>
>> -/*
>> - * 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.
Yeah, start is indeed unchanged, and I think it's also reasonable to
pass it by value rather than 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.
Yeah I didn't notice the details.
I will fix the above two issues in a quick v4 version.
Many thanks for the feedback.
--
Thanks,
Jingbo
Jeff Layton <[email protected]> wrote:
> > +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.
Hmmm. The intention was that the start pointer should be able to be moved
backwards by the cache - but that's not necessary in ->prepare_read() and
->expand_readahead() is provided for that now. So yes, the start pointer
shouldn't get changed at this point.
> 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.
Better to pass the flags in and then ignore them. That way it can tail call,
or just call cachefiles_do_prepare_read() directly from erofs. If you're
going to have a wrapper, then you might be just as well create a
netfs_io_subrequest struct on the stack.
David
On 11/16/22 9:41 PM, David Howells wrote:
> Jeff Layton <[email protected]> wrote:
>
>>> +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.
>
> Hmmm. The intention was that the start pointer should be able to be moved
> backwards by the cache - but that's not necessary in ->prepare_read() and
> ->expand_readahead() is provided for that now. So yes, the start pointer
> shouldn't get changed at this point.
Okay.
>
>> 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.
>
> Better to pass the flags in and then ignore them. That way it can tail call,
> or just call cachefiles_do_prepare_read() directly from erofs. If you're
> going to have a wrapper, then you might be just as well create a
> netfs_io_subrequest struct on the stack.
I would prefer letting cachefiles_prepare_ondemand_read() pass flags in
and then tail call cachefiles_do_prepare_read() directly.
Many thanks for the suggestion.
--
Thanks,
Jingbo