--- /dev/null
+// SPDX-License-Identifier: GPL-2.0-only
+/* Network filesystem high-level write support.
+ *
+ * Copyright (C) 2023 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include <linux/export.h>
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/pagemap.h>
+#include <linux/slab.h>
+#include <linux/pagevec.h>
+#include "internal.h"
+
+/*
+ * Determined write method. Adjust netfs_folio_traces if this is changed.
+ */
+enum netfs_how_to_modify {
+ NETFS_FOLIO_IS_UPTODATE, /* Folio is uptodate already */
+ NETFS_JUST_PREFETCH, /* We have to read the folio anyway */
+ NETFS_WHOLE_FOLIO_MODIFY, /* We're going to overwrite the whole folio */
+ NETFS_MODIFY_AND_CLEAR, /* We can assume there is no data to be downloaded. */
+ NETFS_STREAMING_WRITE, /* Store incomplete data in non-uptodate page. */
+ NETFS_STREAMING_WRITE_CONT, /* Continue streaming write. */
+ NETFS_FLUSH_CONTENT, /* Flush incompatible content. */
+};
+
+static void netfs_set_group(struct folio *folio, struct netfs_group *netfs_group)
+{
+ if (netfs_group && !folio_get_private(folio))
+ folio_attach_private(folio, netfs_get_group(netfs_group));
+}
+
+/*
+ * Decide how we should modify a folio. We might be attempting to do
+ * write-streaming, in which case we don't want to a local RMW cycle if we can
+ * avoid it. If we're doing local caching or content crypto, we award that
+ * priority over avoiding RMW. If the file is open readably, then we also
+ * assume that we may want to read what we wrote.
+ */
+static enum netfs_how_to_modify netfs_how_to_modify(struct netfs_inode *ctx,
+ struct file *file,
+ struct folio *folio,
+ void *netfs_group,
+ size_t flen,
+ size_t offset,
+ size_t len,
+ bool maybe_trouble)
+{
+ struct netfs_folio *finfo = netfs_folio_info(folio);
+ loff_t pos = folio_file_pos(folio);
+
+ _enter("");
+
+ if (netfs_folio_group(folio) != netfs_group)
+ return NETFS_FLUSH_CONTENT;
+
+ if (folio_test_uptodate(folio))
+ return NETFS_FOLIO_IS_UPTODATE;
+
+ if (pos >= ctx->remote_i_size)
+ return NETFS_MODIFY_AND_CLEAR;
+
+ if (!maybe_trouble && offset == 0 && len >= flen)
+ return NETFS_WHOLE_FOLIO_MODIFY;
+
+ if (file->f_mode & FMODE_READ)
+ return NETFS_JUST_PREFETCH;
+
+ if (netfs_is_cache_enabled(ctx))
+ return NETFS_JUST_PREFETCH;
+
+ if (!finfo)
+ return NETFS_STREAMING_WRITE;
+
+ /* We can continue a streaming write only if it continues on from the
+ * previous. If it overlaps, we must flush lest we suffer a partial
+ * copy and disjoint dirty regions.
+ */
+ if (offset == finfo->dirty_offset + finfo->dirty_len)
+ return NETFS_STREAMING_WRITE_CONT;
+ return NETFS_FLUSH_CONTENT;
+}
+
+/*
+ * Grab a folio for writing and lock it.
+ */
+static struct folio *netfs_grab_folio_for_write(struct address_space *mapping,
+ loff_t pos, size_t part)
+{
+ pgoff_t index = pos / PAGE_SIZE;
+
+ return __filemap_get_folio(mapping, index, FGP_WRITEBEGIN,
+ mapping_gfp_mask(mapping));
+}
+
+/**
+ * netfs_perform_write - Copy data into the pagecache.
+ * @iocb: The operation parameters
+ * @iter: The source buffer
+ * @netfs_group: Grouping for dirty pages (eg. ceph snaps).
+ *
+ * Copy data into pagecache pages attached to the inode specified by @iocb.
+ * The caller must hold appropriate inode locks.
+ *
+ * Dirty pages are tagged with a netfs_folio struct if they're not up to date
+ * to indicate the range modified. Dirty pages may also be tagged with a
+ * netfs-specific grouping such that data from an old group gets flushed before
+ * a new one is started.
+ */
+ssize_t netfs_perform_write(struct kiocb *iocb, struct iov_iter *iter,
+ struct netfs_group *netfs_group)
+{
+ struct file *file = iocb->ki_filp;
+ struct inode *inode = file_inode(file);
+ struct address_space *mapping = inode->i_mapping;
+ struct netfs_inode *ctx = netfs_inode(inode);
+ struct netfs_folio *finfo;
+ struct folio *folio;
+ enum netfs_how_to_modify howto;
+ enum netfs_folio_trace trace;
+ unsigned int bdp_flags = (iocb->ki_flags & IOCB_SYNC) ? 0: BDP_ASYNC;
+ ssize_t written = 0, ret;
+ loff_t i_size, pos = iocb->ki_pos, from, to;
+ size_t max_chunk = PAGE_SIZE << MAX_PAGECACHE_ORDER;
+ bool maybe_trouble = false;
+
+ do {
+ size_t flen;
+ size_t offset; /* Offset into pagecache folio */
+ size_t part; /* Bytes to write to folio */
+ size_t copied; /* Bytes copied from user */
+
+ ret = balance_dirty_pages_ratelimited_flags(mapping, bdp_flags);
+ if (unlikely(ret < 0))
+ break;
+
+ offset = pos & (max_chunk - 1);
+ part = min(max_chunk - offset, iov_iter_count(iter));
+
+ /* Bring in the user pages that we will copy from _first_ lest
+ * we hit a nasty deadlock on copying from the same page as
+ * we're writing to, without it being marked uptodate.
+ *
+ * Not only is this an optimisation, but it is also required to
+ * check that the address is actually valid, when atomic
+ * usercopies are used below.
+ *
+ * We rely on the page being held onto long enough by the LRU
+ * that we can grab it below if this causes it to be read.
+ */
+ ret = -EFAULT;
+ if (unlikely(fault_in_iov_iter_readable(iter, part) == part))
+ break;
+
+ ret = -ENOMEM;
+ folio = netfs_grab_folio_for_write(mapping, pos, part);
+ if (!folio)
+ break;
+
+ flen = folio_size(folio);
+ offset = pos & (flen - 1);
+ part = min_t(size_t, flen - offset, part);
+
+ if (signal_pending(current)) {
+ ret = written ? -EINTR : -ERESTARTSYS;
+ goto error_folio_unlock;
+ }
+
+ /* See if we need to prefetch the area we're going to modify.
+ * We need to do this before we get a lock on the folio in case
+ * there's more than one writer competing for the same cache
+ * block.
+ */
+ howto = netfs_how_to_modify(ctx, file, folio, netfs_group,
+ flen, offset, part, maybe_trouble);
+ _debug("howto %u", howto);
+ switch (howto) {
+ case NETFS_JUST_PREFETCH:
+ ret = netfs_prefetch_for_write(file, folio, offset, part);
+ if (ret < 0) {
+ _debug("prefetch = %zd", ret);
+ goto error_folio_unlock;
+ }
+ break;
+ case NETFS_FOLIO_IS_UPTODATE:
+ case NETFS_WHOLE_FOLIO_MODIFY:
+ case NETFS_STREAMING_WRITE_CONT:
+ break;
+ case NETFS_MODIFY_AND_CLEAR:
+ zero_user_segment(&folio->page, 0, offset);
+ break;
+ case NETFS_STREAMING_WRITE:
+ ret = -EIO;
+ if (WARN_ON(folio_get_private(folio)))
+ goto error_folio_unlock;
+ break;
+ case NETFS_FLUSH_CONTENT:
+ trace_netfs_folio(folio, netfs_flush_content);
+ from = folio_pos(folio);
+ to = from + folio_size(folio) - 1;
+ folio_unlock(folio);
+ folio_put(folio);
+ ret = filemap_write_and_wait_range(mapping, from, to);
+ if (ret < 0)
+ goto error_folio_unlock;
+ continue;
+ }
+
+ if (mapping_writably_mapped(mapping))
+ flush_dcache_folio(folio);
+
+ copied = copy_folio_from_iter_atomic(folio, offset, part, iter);
+
+ flush_dcache_folio(folio);
+
+ /* Deal with a (partially) failed copy */
+ if (copied == 0) {
+ ret = -EFAULT;
+ goto error_folio_unlock;
+ }
+
+ trace = (enum netfs_folio_trace)howto;
+ switch (howto) {
+ case NETFS_FOLIO_IS_UPTODATE:
+ case NETFS_JUST_PREFETCH:
+ netfs_set_group(folio, netfs_group);
+ break;
+ case NETFS_MODIFY_AND_CLEAR:
+ zero_user_segment(&folio->page, offset + copied, flen);
+ netfs_set_group(folio, netfs_group);
+ folio_mark_uptodate(folio);
+ break;
+ case NETFS_WHOLE_FOLIO_MODIFY:
+ if (unlikely(copied < part)) {
+ maybe_trouble = true;
+ iov_iter_revert(iter, copied);
+ copied = 0;
+ goto retry;
+ }
+ netfs_set_group(folio, netfs_group);
+ folio_mark_uptodate(folio);
+ break;
+ case NETFS_STREAMING_WRITE:
+ if (offset == 0 && copied == flen) {
+ netfs_set_group(folio, netfs_group);
+ folio_mark_uptodate(folio);
+ trace = netfs_streaming_filled_page;
+ break;
+ }
+ finfo = kzalloc(sizeof(*finfo), GFP_KERNEL);
+ if (!finfo) {
+ iov_iter_revert(iter, copied);
+ ret = -ENOMEM;
+ goto error_folio_unlock;
+ }
+ finfo->netfs_group = netfs_get_group(netfs_group);
+ finfo->dirty_offset = offset;
+ finfo->dirty_len = copied;
+ folio_attach_private(folio, (void *)((unsigned long)finfo |
+ NETFS_FOLIO_INFO));
+ break;
+ case NETFS_STREAMING_WRITE_CONT:
+ finfo = netfs_folio_info(folio);
+ finfo->dirty_len += copied;
+ if (finfo->dirty_offset == 0 && finfo->dirty_len == flen) {
+ if (finfo->netfs_group)
+ folio_change_private(folio, finfo->netfs_group);
+ else
+ folio_detach_private(folio);
+ folio_mark_uptodate(folio);
+ kfree(finfo);
+ trace = netfs_streaming_cont_filled_page;
+ }
+ break;
+ default:
+ WARN(true, "Unexpected modify type %u ix=%lx\n",
+ howto, folio_index(folio));
+ ret = -EIO;
+ goto error_folio_unlock;
+ }
+
+ trace_netfs_folio(folio, trace);
+
+ /* Update the inode size if we moved the EOF marker */
+ i_size = i_size_read(inode);
+ pos += copied;
+ if (pos > i_size) {
+ if (ctx->ops->update_i_size) {
+ ctx->ops->update_i_size(inode, pos);
+ } else {
+ i_size_write(inode, pos);
+#if IS_ENABLED(CONFIG_FSCACHE)
+ fscache_update_cookie(ctx->cache, NULL, &pos);
+#endif
+ }
+ }
+ written += copied;
+
+ folio_mark_dirty(folio);
+ retry:
+ folio_unlock(folio);
+ folio_put(folio);
+ folio = NULL;
+
+ cond_resched();
+ } while (iov_iter_count(iter));
+
+out:
+ if (likely(written)) {
+ /* Flush and wait for a write that requires immediate synchronisation. */
+ if (iocb->ki_flags & (IOCB_DSYNC | IOCB_SYNC)) {
+ _debug("dsync");
+ ret = filemap_fdatawait_range(mapping, iocb->ki_pos,
+ iocb->ki_pos + written);
+ }
+
+ iocb->ki_pos += written;
+ }
+
+ _leave(" = %zd [%zd]", written, ret);
+ return written ? written : ret;
+
+error_folio_unlock:
+ folio_unlock(folio);
+ folio_put(folio);
+ goto out;
+}
+EXPORT_SYMBOL(netfs_perform_write);
EM(netfs_read_trace_expanded, "EXPANDED ") \
EM(netfs_read_trace_readahead, "READAHEAD") \
EM(netfs_read_trace_readpage, "READPAGE ") \
+ EM(netfs_read_trace_prefetch_for_write, "PREFETCHW") \
E_(netfs_read_trace_write_begin, "WRITEBEGN")
#define netfs_write_traces \
EM(netfs_sreq_trace_put_work, "PUT WORK ") \
E_(netfs_sreq_trace_put_terminated, "PUT TERM ")
+#define netfs_folio_traces \
+ /* The first few correspond to enum netfs_how_to_modify */ \
+ EM(netfs_folio_is_uptodate, "mod-uptodate") \
+ EM(netfs_just_prefetch, "mod-prefetch") \
+ EM(netfs_whole_folio_modify, "mod-whole-f") \
+ EM(netfs_modify_and_clear, "mod-n-clear") \
+ EM(netfs_streaming_write, "mod-streamw") \
+ EM(netfs_streaming_write_cont, "mod-streamw+") \
+ EM(netfs_flush_content, "flush") \
+ EM(netfs_streaming_filled_page, "mod-streamw-f") \
+ EM(netfs_streaming_cont_filled_page, "mod-streamw-f+") \
+ /* The rest are for writeback */ \
+ EM(netfs_folio_trace_clear, "clear") \
+ EM(netfs_folio_trace_clear_s, "clear-s") \
+ EM(netfs_folio_trace_clear_g, "clear-g") \
+ EM(netfs_folio_trace_copy_to_cache, "copy") \
+ EM(netfs_folio_trace_end_copy, "end-copy") \
+ EM(netfs_folio_trace_kill, "kill") \
+ EM(netfs_folio_trace_mkwrite, "mkwrite") \
+ EM(netfs_folio_trace_mkwrite_plus, "mkwrite+") \
+ EM(netfs_folio_trace_redirty, "redirty") \
+ EM(netfs_folio_trace_redirtied, "redirtied") \
+ EM(netfs_folio_trace_store, "store") \
+ E_(netfs_folio_trace_store_plus, "store+")
+
#ifndef __NETFS_DECLARE_TRACE_ENUMS_ONCE_ONLY
#define __NETFS_DECLARE_TRACE_ENUMS_ONCE_ONLY
enum netfs_failure { netfs_failures } __mode(byte);
enum netfs_rreq_ref_trace { netfs_rreq_ref_traces } __mode(byte);
enum netfs_sreq_ref_trace { netfs_sreq_ref_traces } __mode(byte);
+enum netfs_folio_trace { netfs_folio_traces } __mode(byte);
#endif
netfs_failures;
netfs_rreq_ref_traces;
netfs_sreq_ref_traces;
+netfs_folio_traces;
/*
* Now redefine the EM() and E_() macros to map the enums to the strings that
__entry->ref)
);
+TRACE_EVENT(netfs_folio,
+ TP_PROTO(struct folio *folio, enum netfs_folio_trace why),
+
+ TP_ARGS(folio, why),
+
+ TP_STRUCT__entry(
+ __field(ino_t, ino)
+ __field(pgoff_t, index)
+ __field(unsigned int, nr)
+ __field(enum netfs_folio_trace, why)
+ ),
+
+ TP_fast_assign(
+ __entry->ino = folio->mapping->host->i_ino;
+ __entry->why = why;
+ __entry->index = folio_index(folio);
+ __entry->nr = folio_nr_pages(folio);
+ ),
+
+ TP_printk("i=%05lx ix=%05lx-%05lx %s",
+ __entry->ino, __entry->index, __entry->index + __entry->nr - 1,
+ __print_symbolic(__entry->why, netfs_folio_traces))
+ );
+
+TRACE_EVENT(netfs_write_iter,
+ TP_PROTO(const struct kiocb *iocb, const struct iov_iter *from),
+
+ TP_ARGS(iocb, from),
+
+ TP_STRUCT__entry(
+ __field(unsigned long long, start )
+ __field(size_t, len )
+ __field(unsigned int, flags )
+ ),
+
+ TP_fast_assign(
+ __entry->start = iocb->ki_pos;
+ __entry->len = iov_iter_count(from);
+ __entry->flags = iocb->ki_flags;
+ ),
+
+ TP_printk("WRITE-ITER s=%llx l=%zx f=%x",
+ __entry->start, __entry->len, __entry->flags)
+ );
+
TRACE_EVENT(netfs_write,
TP_PROTO(const struct netfs_io_request *wreq,
enum netfs_write_trace what),
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