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authorDavid Howells <dhowells@redhat.com>2022-01-27 16:02:50 +0000
committerSteve French <stfrench@microsoft.com>2022-02-01 10:29:18 -0600
commitbee9f65523218e3baeeecde9295c8fbe9bc08e0a (patch)
treee13793dfdc27b40a31150029b30904f0eba699d3 /fs/cachefiles
parent052e04a52dcd3359ba1df25a508a3a93707a3f6e (diff)
netfs, cachefiles: Add a method to query presence of data in the cache
Add a netfs_cache_ops method by which a network filesystem can ask the cache about what data it has available and where so that it can make a multipage read more efficient. Signed-off-by: David Howells <dhowells@redhat.com> cc: linux-cachefs@redhat.com Acked-by: Jeff Layton <jlayton@kernel.org> Reviewed-by: Rohith Surabattula <rohiths@microsoft.com> Signed-off-by: Steve French <stfrench@microsoft.com>
Diffstat (limited to 'fs/cachefiles')
-rw-r--r--fs/cachefiles/io.c59
1 files changed, 59 insertions, 0 deletions
diff --git a/fs/cachefiles/io.c b/fs/cachefiles/io.c
index 04eb52736990..753986ea1583 100644
--- a/fs/cachefiles/io.c
+++ b/fs/cachefiles/io.c
@@ -192,6 +192,64 @@ presubmission_error:
}
/*
+ * Query the occupancy of the cache in a region, returning where the next chunk
+ * of data starts and how long it is.
+ */
+static int cachefiles_query_occupancy(struct netfs_cache_resources *cres,
+ loff_t start, size_t len, size_t granularity,
+ loff_t *_data_start, size_t *_data_len)
+{
+ struct cachefiles_object *object;
+ struct file *file;
+ loff_t off, off2;
+
+ *_data_start = -1;
+ *_data_len = 0;
+
+ if (!fscache_wait_for_operation(cres, FSCACHE_WANT_READ))
+ return -ENOBUFS;
+
+ object = cachefiles_cres_object(cres);
+ file = cachefiles_cres_file(cres);
+ granularity = max_t(size_t, object->volume->cache->bsize, granularity);
+
+ _enter("%pD,%li,%llx,%zx/%llx",
+ file, file_inode(file)->i_ino, start, len,
+ i_size_read(file_inode(file)));
+
+ off = cachefiles_inject_read_error();
+ if (off == 0)
+ off = vfs_llseek(file, start, SEEK_DATA);
+ if (off == -ENXIO)
+ return -ENODATA; /* Beyond EOF */
+ if (off < 0 && off >= (loff_t)-MAX_ERRNO)
+ return -ENOBUFS; /* Error. */
+ if (round_up(off, granularity) >= start + len)
+ return -ENODATA; /* No data in range */
+
+ off2 = cachefiles_inject_read_error();
+ if (off2 == 0)
+ off2 = vfs_llseek(file, off, SEEK_HOLE);
+ if (off2 == -ENXIO)
+ return -ENODATA; /* Beyond EOF */
+ if (off2 < 0 && off2 >= (loff_t)-MAX_ERRNO)
+ return -ENOBUFS; /* Error. */
+
+ /* Round away partial blocks */
+ off = round_up(off, granularity);
+ off2 = round_down(off2, granularity);
+ if (off2 <= off)
+ return -ENODATA;
+
+ *_data_start = off;
+ if (off2 > start + len)
+ *_data_len = len;
+ else
+ *_data_len = off2 - off;
+ return 0;
+}
+
+/*
* Handle completion of a write to the cache.
*/
static void cachefiles_write_complete(struct kiocb *iocb, long ret)
@@ -545,6 +603,7 @@ static const struct netfs_cache_ops cachefiles_netfs_cache_ops = {
.write = cachefiles_write,
.prepare_read = cachefiles_prepare_read,
.prepare_write = cachefiles_prepare_write,
+ .query_occupancy = cachefiles_query_occupancy,
};
/*