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netfs: Adjust docs after foliation
Adjust the netfslib docs in light of the foliation changes. Also un-kdoc-mark netfs_skip_folio_read() since it's internal and isn't part of the API. Signed-off-by: David Howells <dhowells@redhat.com> Reviewed-by: Jeff Layton <jlayton@redhat.com> cc: Matthew Wilcox <willy@infradead.org> cc: linux-cachefs@redhat.com cc: linux-mm@kvack.org Link: https://lore.kernel.org/r/163706992597.3179783.18360472879717076435.stgit@warthog.procyon.org.uk/ Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
David Howells
Linus Torvalds
parent
d58071a8a7
commit
ddca5b0eba
2 changed files with 58 additions and 41 deletions
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@ -1,7 +1,7 @@
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.. SPDX-License-Identifier: GPL-2.0
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=================================
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NETWORK FILESYSTEM HELPER LIBRARY
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Network Filesystem Helper Library
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=================================
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.. Contents:
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@ -37,22 +37,22 @@ into a common call framework.
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The following services are provided:
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* Handles transparent huge pages (THPs).
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* Handle folios that span multiple pages.
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* Insulates the netfs from VM interface changes.
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* Insulate the netfs from VM interface changes.
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* Allows the netfs to arbitrarily split reads up into pieces, even ones that
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don't match page sizes or page alignments and that may cross pages.
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* Allow the netfs to arbitrarily split reads up into pieces, even ones that
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don't match folio sizes or folio alignments and that may cross folios.
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* Allows the netfs to expand a readahead request in both directions to meet
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its needs.
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* Allow the netfs to expand a readahead request in both directions to meet its
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needs.
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* Allows the netfs to partially fulfil a read, which will then be resubmitted.
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* Allow the netfs to partially fulfil a read, which will then be resubmitted.
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* Handles local caching, allowing cached data and server-read data to be
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* Handle local caching, allowing cached data and server-read data to be
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interleaved for a single request.
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* Handles clearing of bufferage that aren't on the server.
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* Handle clearing of bufferage that aren't on the server.
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* Handle retrying of reads that failed, switching reads from the cache to the
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server as necessary.
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@ -70,22 +70,22 @@ Read Helper Functions
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Three read helpers are provided::
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* void netfs_readahead(struct readahead_control *ractl,
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const struct netfs_read_request_ops *ops,
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void *netfs_priv);``
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* int netfs_readpage(struct file *file,
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struct page *page,
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const struct netfs_read_request_ops *ops,
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void *netfs_priv);
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* int netfs_write_begin(struct file *file,
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struct address_space *mapping,
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loff_t pos,
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unsigned int len,
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unsigned int flags,
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struct page **_page,
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void **_fsdata,
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const struct netfs_read_request_ops *ops,
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void *netfs_priv);
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void netfs_readahead(struct readahead_control *ractl,
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const struct netfs_read_request_ops *ops,
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void *netfs_priv);
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int netfs_readpage(struct file *file,
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struct folio *folio,
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const struct netfs_read_request_ops *ops,
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void *netfs_priv);
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int netfs_write_begin(struct file *file,
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struct address_space *mapping,
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loff_t pos,
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unsigned int len,
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unsigned int flags,
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struct folio **_folio,
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void **_fsdata,
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const struct netfs_read_request_ops *ops,
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void *netfs_priv);
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Each corresponds to a VM operation, with the addition of a couple of parameters
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for the use of the read helpers:
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@ -103,8 +103,8 @@ Both of these values will be stored into the read request structure.
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For ->readahead() and ->readpage(), the network filesystem should just jump
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into the corresponding read helper; whereas for ->write_begin(), it may be a
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little more complicated as the network filesystem might want to flush
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conflicting writes or track dirty data and needs to put the acquired page if an
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error occurs after calling the helper.
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conflicting writes or track dirty data and needs to put the acquired folio if
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an error occurs after calling the helper.
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The helpers manage the read request, calling back into the network filesystem
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through the suppplied table of operations. Waits will be performed as
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@ -253,7 +253,7 @@ through which it can issue requests and negotiate::
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void (*issue_op)(struct netfs_read_subrequest *subreq);
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bool (*is_still_valid)(struct netfs_read_request *rreq);
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int (*check_write_begin)(struct file *file, loff_t pos, unsigned len,
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struct page *page, void **_fsdata);
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struct folio *folio, void **_fsdata);
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void (*done)(struct netfs_read_request *rreq);
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void (*cleanup)(struct address_space *mapping, void *netfs_priv);
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};
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@ -313,13 +313,14 @@ The operations are as follows:
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There is no return value; the netfs_subreq_terminated() function should be
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called to indicate whether or not the operation succeeded and how much data
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it transferred. The filesystem also should not deal with setting pages
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it transferred. The filesystem also should not deal with setting folios
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uptodate, unlocking them or dropping their refs - the helpers need to deal
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with this as they have to coordinate with copying to the local cache.
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Note that the helpers have the pages locked, but not pinned. It is possible
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to use the ITER_XARRAY iov iterator to refer to the range of the inode that
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is being operated upon without the need to allocate large bvec tables.
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Note that the helpers have the folios locked, but not pinned. It is
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possible to use the ITER_XARRAY iov iterator to refer to the range of the
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inode that is being operated upon without the need to allocate large bvec
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tables.
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* ``is_still_valid()``
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@ -330,15 +331,15 @@ The operations are as follows:
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* ``check_write_begin()``
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[Optional] This is called from the netfs_write_begin() helper once it has
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allocated/grabbed the page to be modified to allow the filesystem to flush
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allocated/grabbed the folio to be modified to allow the filesystem to flush
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conflicting state before allowing it to be modified.
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It should return 0 if everything is now fine, -EAGAIN if the page should be
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It should return 0 if everything is now fine, -EAGAIN if the folio should be
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regrabbed and any other error code to abort the operation.
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* ``done``
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[Optional] This is called after the pages in the request have all been
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[Optional] This is called after the folios in the request have all been
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unlocked (and marked uptodate if applicable).
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* ``cleanup``
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@ -390,7 +391,7 @@ The read helpers work by the following general procedure:
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* If NETFS_SREQ_CLEAR_TAIL was set, a short read will be cleared to the
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end of the slice instead of reissuing.
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* Once the data is read, the pages that have been fully read/cleared:
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* Once the data is read, the folios that have been fully read/cleared:
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* Will be marked uptodate.
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@ -398,11 +399,11 @@ The read helpers work by the following general procedure:
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* Unlocked
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* Any pages that need writing to the cache will then have DIO writes issued.
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* Any folios that need writing to the cache will then have DIO writes issued.
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* Synchronous operations will wait for reading to be complete.
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* Writes to the cache will proceed asynchronously and the pages will have the
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* Writes to the cache will proceed asynchronously and the folios will have the
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PG_fscache mark removed when that completes.
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* The request structures will be cleaned up when everything has completed.
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@ -452,6 +453,9 @@ operation table looks like the following::
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netfs_io_terminated_t term_func,
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void *term_func_priv);
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int (*prepare_write)(struct netfs_cache_resources *cres,
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loff_t *_start, size_t *_len, loff_t i_size);
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int (*write)(struct netfs_cache_resources *cres,
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loff_t start_pos,
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struct iov_iter *iter,
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@ -509,6 +513,14 @@ The methods defined in the table are:
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indicating whether the termination is definitely happening in the caller's
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context.
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* ``prepare_write()``
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[Required] Called to adjust a write to the cache and check that there is
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sufficient space in the cache. The start and length values indicate the
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size of the write that netfslib is proposing, and this can be adjusted by
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the cache to respect DIO boundaries. The file size is passed for
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information.
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* ``write()``
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[Required] Called to write to the cache. The start file offset is given
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@ -525,4 +537,9 @@ not the read request structure as they could be used in other situations where
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there isn't a read request structure as well, such as writing dirty data to the
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cache.
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API Function Reference
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======================
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.. kernel-doc:: include/linux/netfs.h
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.. kernel-doc:: fs/netfs/read_helper.c
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@ -1008,8 +1008,8 @@ int netfs_readpage(struct file *file,
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}
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EXPORT_SYMBOL(netfs_readpage);
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/**
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* netfs_skip_folio_read - prep a folio for writing without reading first
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/*
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* Prepare a folio for writing without reading first
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* @folio: The folio being prepared
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* @pos: starting position for the write
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* @len: length of write
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