[Linux-cachefs] [PATCH v4 03/10] cachefiles: Always indicate we should fill a post-EOF page with zeros

[David Howells]

In cachefiles_prepare_read(), always indicate to the netfs lib that a page
beyond the EOF should be filled with zeros, even if we don't have a cache
file attached because it's still being created.

This avoids confusion in netfs_rreq_prepare_read() where it sees source ==
NETFS_DOWNLOAD_FROM_SERVER, where it consequently sees the read after the
EOF getting reduced to 0 size and thus triggers the WARN_ON and marking the
read invalid.

Also don't try to check for data if there's a flag set indicating we don't
yet have anything stored in the cache.

Signed-off-by: David Howells <dhowe...@redhat.com>
---

 fs/cachefiles/io.c |   29 +++++++++++++++++------------
 1 file changed, 17 insertions(+), 12 deletions(-)

diff --git a/fs/cachefiles/io.c b/fs/cachefiles/io.c
index 08b3183e0dce..dbc1c4421116 100644
--- a/fs/cachefiles/io.c
+++ b/fs/cachefiles/io.c
@@ -273,6 +273,7 @@ static enum netfs_read_source 
cachefiles_prepare_read(struct netfs_read_subreque
        struct cachefiles_cache *cache;
        const struct cred *saved_cred;
        struct file *file = subreq->rreq->cache_resources.cache_priv2;
+       enum netfs_read_source ret = NETFS_DOWNLOAD_FROM_SERVER;
        loff_t off, to;
 
        _enter("%zx @%llx/%llx", subreq->len, subreq->start, i_size);
@@ -281,19 +282,24 @@ static enum netfs_read_source 
cachefiles_prepare_read(struct netfs_read_subreque
        cache = container_of(object->fscache.cache,
                             struct cachefiles_cache, cache);
 
-       if (!file)
-               goto cache_fail_nosec;
+       cachefiles_begin_secure(cache, &saved_cred);
 
-       if (subreq->start >= i_size)
-               return NETFS_FILL_WITH_ZEROES;
+       if (subreq->start >= i_size) {
+               ret = NETFS_FILL_WITH_ZEROES;
+               goto out;
+       }
 
-       cachefiles_begin_secure(cache, &saved_cred);
+       if (!file)
+               goto out;
+
+       if (test_bit(FSCACHE_COOKIE_NO_DATA_YET, 
&object->fscache.cookie->flags))
+               goto download_and_store;
 
        off = vfs_llseek(file, subreq->start, SEEK_DATA);
        if (off < 0 && off >= (loff_t)-MAX_ERRNO) {
                if (off == (loff_t)-ENXIO)
                        goto download_and_store;
-               goto cache_fail;
+               goto out;
        }
 
        if (off >= subreq->start + subreq->len)
@@ -307,7 +313,7 @@ static enum netfs_read_source 
cachefiles_prepare_read(struct netfs_read_subreque
 
        to = vfs_llseek(file, subreq->start, SEEK_HOLE);
        if (to < 0 && to >= (loff_t)-MAX_ERRNO)
-               goto cache_fail;
+               goto out;
 
        if (to < subreq->start + subreq->len) {
                if (subreq->start + subreq->len >= i_size)
@@ -317,16 +323,15 @@ static enum netfs_read_source 
cachefiles_prepare_read(struct netfs_read_subreque
                subreq->len = to - subreq->start;
        }
 
-       cachefiles_end_secure(cache, saved_cred);
-       return NETFS_READ_FROM_CACHE;
+       ret = NETFS_READ_FROM_CACHE;
+       goto out;
 
 download_and_store:
        if (cachefiles_has_space(cache, 0, (subreq->len + PAGE_SIZE - 1) / 
PAGE_SIZE) == 0)
                __set_bit(NETFS_SREQ_WRITE_TO_CACHE, &subreq->flags);
-cache_fail:
+out:
        cachefiles_end_secure(cache, saved_cred);
-cache_fail_nosec:
-       return NETFS_DOWNLOAD_FROM_SERVER;
+       return ret;
 }
 
 /*


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