lwn.git/include/linux/nfs_page.h, branch v6.4-rc4

NFS: Convert buffered read paths to use netfs when fscache is enabled

2023-04-11T17:08:26+00:00

Convert the NFS buffered read code paths to corresponding netfs APIs, but only when fscache is configured and enabled. The netfs API defines struct netfs_request_ops which must be filled in by the network filesystem. For NFS, we only need to define 5 of the functions, the main one being the issue_read() function. The issue_read() function is called by the netfs layer when a read cannot be fulfilled locally, and must be sent to the server (either the cache is not active, or it is active but the data is not available). Once the read from the server is complete, netfs requires a call to netfs_subreq_terminated() which conveys either how many bytes were read successfully, or an error. Note that issue_read() is called with a structure, netfs_io_subrequest, which defines the IO requested, and contains a start and a length (both in bytes), and assumes the underlying netfs will return a either an error on the whole region, or the number of bytes successfully read. The NFS IO path is page based and the main APIs are the pgio APIs defined in pagelist.c. For the pgio APIs, there is no way for the caller to know how many RPCs will be sent and how the pages will be broken up into underlying RPCs, each of which will have their own completion and return code. In contrast, netfs is subrequest based, a single subrequest may contain multiple pages, and a single subrequest is initiated with issue_read() and terminated with netfs_subreq_terminated(). Thus, to utilze the netfs APIs, NFS needs some way to accommodate the netfs API requirement on the single response to the whole subrequest, while also minimizing disruptive changes to the NFS pgio layer. The approach taken with this patch is to allocate a small structure for each nfs_netfs_issue_read() call, store the final error and number of bytes successfully transferred in the structure, and update these values as each RPC completes. The refcount on the structure is used as a marker for the last RPC completion, is incremented in nfs_netfs_read_initiate(), and decremented inside nfs_netfs_read_completion(), when a nfs_pgio_header contains a valid pointer to the data. On the final put (which signals the final outstanding RPC is complete) in nfs_netfs_read_completion(), call netfs_subreq_terminated() with either the final error value (if one or more READs complete with an error) or the number of bytes successfully transferred (if all RPCs complete successfully). Note that when all RPCs complete successfully, the number of bytes transferred is capped to the length of the subrequest. Capping the transferred length to the subrequest length prevents "Subreq overread" warnings from netfs. This is due to the "aligned_len" in nfs_pageio_add_page(), and the corner case where NFS requests a full page at the end of the file, even when i_size reflects only a partial page (NFS overread). Signed-off-by: Dave Wysochanski Tested-by: Daire Byrne Signed-off-by: Anna Schumaker

NFS: Clean up O_DIRECT request allocation

2023-02-14T19:22:33+00:00

Rather than adjusting the index+offset after the call to nfs_create_request(), add a function nfs_page_create_from_page() that takes an offset. Signed-off-by: Trond Myklebust Signed-off-by: Anna Schumaker

NFS: Convert buffered reads to use folios

2023-02-14T19:22:32+00:00

Perform a largely mechanical conversion of references to struct page and page-specific functions to use the folio equivalents. Note that the fscache functionality remains untouched. Instead we just pass in the folio page. This should be OK, as long as we use order 0 folios together with fscache. Signed-off-by: Trond Myklebust Signed-off-by: Anna Schumaker

NFS: Add a helper to convert a struct nfs_page into an inode

2023-02-14T19:22:32+00:00

Replace all the open coded calls to page_file_mapping(req->wb_page)->host. Signed-off-by: Trond Myklebust Signed-off-by: Anna Schumaker

NFS: Fix nfs_coalesce_size() to work with folios

2023-02-14T19:22:32+00:00

Use the helper folio_size() where appropriate. Signed-off-by: Trond Myklebust Signed-off-by: Anna Schumaker

NFS: Add basic functionality for tracking folios in struct nfs_page

2023-02-14T19:22:32+00:00

Signed-off-by: Trond Myklebust Signed-off-by: Anna Schumaker

NFS: Improve write error tracing

2022-08-09T18:11:34+00:00

Don't leak request pointers, but use the "device:inode" labelling that is used by all the other trace points. Furthermore, replace use of page indexes with an offset, again in order to align behaviour with other NFS trace points. Signed-off-by: Trond Myklebust

pNFS/flexfiles: Fix array overflow when flexfiles mirroring is enabled

2020-11-30T15:52:22+00:00

If the flexfiles mirroring is enabled, then the read code expects to be able to set pgio->pg_mirror_idx to point to the data server that is being used for this particular read. However it does not change the pg_mirror_count because we only need to send a single read. Signed-off-by: Trond Myklebust Signed-off-by: Anna Schumaker

NFS: Try to join page groups before an O_DIRECT retransmission

2020-04-01T17:37:57+00:00

If we have to retransmit requests, try to join their page groups first. Signed-off-by: Trond Myklebust

NFS: Refactor nfs_lock_and_join_requests()

2020-04-01T17:37:56+00:00

Refactor nfs_lock_and_join_requests() in order to separate out the subrequest merging into its own function nfs_lock_and_join_group() that can be used by O_DIRECT. Signed-off-by: Trond Myklebust