[PATCH v4 33/39] netfs, cachefiles: Pass upper bound length to allow expansion

David Howells
2023-12-13T15:26:29Z

Make netfslib pass the maximum length to the ->prepare_write() op to tell
the cache how much it can expand the length of a write to. This allows a
write to the server at the end of a file to be limited to a few bytes
whilst writing an entire block to the cache (something required by direct
I/O).

Signed-off-by: David Howells <dhowells@redhat.com>
cc: Jeff Layton <jlayton@kernel.org>
cc: linux-cachefs@redhat.com
cc: linux-fsdevel@vger.kernel.org
cc: linux-mm@kvack.org
---
fs/cachefiles/internal.h | 2 +-
fs/cachefiles/io.c | 10 ++++++----
fs/cachefiles/ondemand.c | 2 +-
fs/netfs/fscache_io.c | 2 +-
fs/netfs/io.c | 2 +-
fs/netfs/objects.c | 1 +
fs/netfs/output.c | 25 ++++++++++---------------
fs/smb/client/fscache.c | 2 +-
include/linux/netfs.h | 5 +++--
9 files changed, 25 insertions(+), 26 deletions(-)

diff --git a/fs/cachefiles/internal.h b/fs/cachefiles/internal.h
index 4a87c9d714a9..d33169f0018b 100644
--- a/fs/cachefiles/internal.h
+++ b/fs/cachefiles/internal.h
@@ -246,7 +246,7 @@ extern bool cachefiles_begin_operation(struct netfs_cache_resources *cres,
enum fscache_want_state want_state);
extern int __cachefiles_prepare_write(struct cachefiles_object *object,
struct file *file,
- loff_t *_start, size_t *_len,
+ loff_t *_start, size_t *_len, size_t upper_len,
bool no_space_allocated_yet);
extern int __cachefiles_write(struct cachefiles_object *object,
struct file *file,
diff --git a/fs/cachefiles/io.c b/fs/cachefiles/io.c
index 5857241c5918..9fe69a60eb24 100644
--- a/fs/cachefiles/io.c
+++ b/fs/cachefiles/io.c
@@ -517,7 +517,7 @@ cachefiles_prepare_ondemand_read(struct netfs_cache_resources *cres,
*/
int __cachefiles_prepare_write(struct cachefiles_object *object,
struct file *file,
- loff_t *_start, size_t *_len,
+ loff_t *_start, size_t *_len, size_t upper_len,
bool no_space_allocated_yet)
{
struct cachefiles_cache *cache = object->volume->cache;
@@ -529,6 +529,8 @@ int __cachefiles_prepare_write(struct cachefiles_object *object,
down = start - round_down(start, PAGE_SIZE);
*_start = start - down;
*_len = round_up(down + len, PAGE_SIZE);
+ if (down < start || *_len > upper_len)
+ return -ENOBUFS;

/* We need to work out whether there's sufficient disk space to perform
* the write - but we can skip that check if we have space already
@@ -591,8 +593,8 @@ int __cachefiles_prepare_write(struct cachefiles_object *object,
}

static int cachefiles_prepare_write(struct netfs_cache_resources *cres,
- loff_t *_start, size_t *_len, loff_t i_size,
- bool no_space_allocated_yet)
+ loff_t *_start, size_t *_len, size_t upper_len,
+ loff_t i_size, bool no_space_allocated_yet)
{
struct cachefiles_object *object = cachefiles_cres_object(cres);
struct cachefiles_cache *cache = object->volume->cache;
@@ -608,7 +610,7 @@ static int cachefiles_prepare_write(struct netfs_cache_resources *cres,

cachefiles_begin_secure(cache, &saved_cred);
ret = __cachefiles_prepare_write(object, cachefiles_cres_file(cres),
- _start, _len,
+ _start, _len, upper_len,
no_space_allocated_yet);
cachefiles_end_secure(cache, saved_cred);
return ret;
diff --git a/fs/cachefiles/ondemand.c b/fs/cachefiles/ondemand.c
index b8fbbb1961bb..5fd74ec60bef 100644
--- a/fs/cachefiles/ondemand.c
+++ b/fs/cachefiles/ondemand.c
@@ -50,7 +50,7 @@ static ssize_t cachefiles_ondemand_fd_write_iter(struct kiocb *kiocb,
return -ENOBUFS;

cachefiles_begin_secure(cache, &saved_cred);
- ret = __cachefiles_prepare_write(object, file, &pos, &len, true);
+ ret = __cachefiles_prepare_write(object, file, &pos, &len, len, true);
cachefiles_end_secure(cache, saved_cred);
if (ret < 0)
return ret;
diff --git a/fs/netfs/fscache_io.c b/fs/netfs/fscache_io.c
index 79171a687930..ad572f7ee897 100644
--- a/fs/netfs/fscache_io.c
+++ b/fs/netfs/fscache_io.c
@@ -237,7 +237,7 @@ void __fscache_write_to_cache(struct fscache_cookie *cookie,
fscache_access_io_write) < 0)
goto abandon_free;

- ret = cres->ops->prepare_write(cres, &start, &len, i_size, false);
+ ret = cres->ops->prepare_write(cres, &start, &len, len, i_size, false);
if (ret < 0)
goto abandon_end;

diff --git a/fs/netfs/io.c b/fs/netfs/io.c
index 894c3305710d..5d9098db815a 100644
--- a/fs/netfs/io.c
+++ b/fs/netfs/io.c
@@ -199,7 +199,7 @@ static void netfs_rreq_do_write_to_cache(struct netfs_io_request *rreq)
}

ret = cres->ops->prepare_write(cres, &subreq->start, &subreq->len,
- rreq->i_size, true);
+ subreq->len, rreq->i_size, true);
if (ret < 0) {
trace_netfs_failure(rreq, subreq, ret, netfs_fail_prepare_write);
trace_netfs_sreq(subreq, netfs_sreq_trace_write_skip);
diff --git a/fs/netfs/objects.c b/fs/netfs/objects.c
index c1218b183197..16252cc4576e 100644
--- a/fs/netfs/objects.c
+++ b/fs/netfs/objects.c
@@ -33,6 +33,7 @@ struct netfs_io_request *netfs_alloc_request(struct address_space *mapping,

rreq->start = start;
rreq->len = len;
+ rreq->upper_len = len;
rreq->origin = origin;
rreq->netfs_ops = ctx->ops;
rreq->mapping = mapping;
diff --git a/fs/netfs/output.c b/fs/netfs/output.c
index 560cbcea0c0a..cc9065733b42 100644
--- a/fs/netfs/output.c
+++ b/fs/netfs/output.c
@@ -280,7 +280,7 @@ EXPORT_SYMBOL(netfs_queue_write_request);
*/
static void netfs_set_up_write_to_cache(struct netfs_io_request *wreq)
{
- struct netfs_cache_resources *cres;
+ struct netfs_cache_resources *cres = &wreq->cache_resources;
struct netfs_io_subrequest *subreq;
struct netfs_inode *ctx = netfs_inode(wreq->inode);
struct fscache_cookie *cookie = netfs_i_cookie(ctx);
@@ -294,26 +294,21 @@ static void netfs_set_up_write_to_cache(struct netfs_io_request *wreq)
}

_debug("write to cache");
- subreq = netfs_create_write_request(wreq, NETFS_WRITE_TO_CACHE, start, len,
- netfs_write_to_cache_op_worker);
- if (!subreq)
+ ret = fscache_begin_write_operation(cres, cookie);
+ if (ret < 0)
return;

- cres = &wreq->cache_resources;
- ret = fscache_begin_read_operation(cres, cookie);
- if (ret < 0) {
- netfs_write_subrequest_terminated(subreq, ret, false);
+ ret = cres->ops->prepare_write(cres, &start, &len, wreq->upper_len,
+ i_size_read(wreq->inode), true);
+ if (ret < 0)
return;
- }

- ret = cres->ops->prepare_write(cres, &start, &len, i_size_read(wreq->inode),
- true);
- if (ret < 0) {
- netfs_write_subrequest_terminated(subreq, ret, false);
+ subreq = netfs_create_write_request(wreq, NETFS_WRITE_TO_CACHE, start, len,
+ netfs_write_to_cache_op_worker);
+ if (!subreq)
return;
- }

- netfs_queue_write_request(subreq);
+ netfs_write_to_cache_op(subreq);
}

/*
diff --git a/fs/smb/client/fscache.c b/fs/smb/client/fscache.c
index e5cad149f5a2..c4a3cb736881 100644
--- a/fs/smb/client/fscache.c
+++ b/fs/smb/client/fscache.c
@@ -180,7 +180,7 @@ static int fscache_fallback_write_pages(struct inode *inode, loff_t start, size_
if (ret < 0)
return ret;

- ret = cres.ops->prepare_write(&cres, &start, &len, i_size_read(inode),
+ ret = cres.ops->prepare_write(&cres, &start, &len, len, i_size_read(inode),
no_space_allocated_yet);
if (ret == 0)
ret = fscache_write(&cres, start, &iter, NULL, NULL);
diff --git a/include/linux/netfs.h b/include/linux/netfs.h
index 638f42fdaef5..f98deef22d06 100644
--- a/include/linux/netfs.h
+++ b/include/linux/netfs.h
@@ -263,6 +263,7 @@ struct netfs_io_request {
atomic_t nr_copy_ops; /* Number of copy-to-cache ops in progress */
size_t submitted; /* Amount submitted for I/O so far */
size_t len; /* Length of the request */
+ size_t upper_len; /* Length can be extended to here */
size_t transferred; /* Amount to be indicated as transferred */
short error; /* 0 or error that occurred */
enum netfs_io_origin origin; /* Origin of the request */
@@ -360,8 +361,8 @@ struct netfs_cache_ops {
* actually do.
*/
int (*prepare_write)(struct netfs_cache_resources *cres,
- loff_t *_start, size_t *_len, loff_t i_size,
- bool no_space_allocated_yet);
+ loff_t *_start, size_t *_len, size_t upper_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.