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Message-ID: <522331.1677800209@warthog.procyon.org.uk>
Date: Thu, 02 Mar 2023 23:36:49 +0000
From: David Howells <dhowells@...hat.com>
To: Linus Torvalds <torvalds@...ux-foundation.org>,
Steve French <smfrench@...il.com>
Cc: dhowells@...hat.com, Vishal Moola <vishal.moola@...il.com>,
Shyam Prasad N <nspmangalore@...il.com>,
Rohith Surabattula <rohiths.msft@...il.com>,
Tom Talpey <tom@...pey.com>,
Stefan Metzmacher <metze@...ba.org>,
Paulo Alcantara <pc@....nz>, Jeff Layton <jlayton@...nel.org>,
Matthew Wilcox <willy@...radead.org>,
Marc Dionne <marc.dionne@...istor.com>,
linux-afs@...ts.infradead.org, linux-cifs@...r.kernel.org,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: cifs test patch to convert to using write_cache_pages()
David Howells <dhowells@...hat.com> wrote:
> And then CIFS. ...
>
> Base + write_cache_pages():
> WRITE: bw=457MiB/s (479MB/s), 114MiB/s-114MiB/s (120MB/s-120MB/s)
> WRITE: bw=449MiB/s (471MB/s), 112MiB/s-113MiB/s (118MB/s-118MB/s)
> WRITE: bw=459MiB/s (482MB/s), 115MiB/s-115MiB/s (120MB/s-121MB/s)
Here's my patch to convert cifs to use write_cache_pages().
David
---
fs/cifs/file.c | 400 ++++++++++++++++-----------------------------------------
1 file changed, 115 insertions(+), 285 deletions(-)
diff --git a/fs/cifs/file.c b/fs/cifs/file.c
index 3d304d4a54d6..04e2466609d9 100644
--- a/fs/cifs/file.c
+++ b/fs/cifs/file.c
@@ -2613,140 +2613,35 @@ static int cifs_partialpagewrite(struct page *page, unsigned from, unsigned to)
return rc;
}
-/*
- * Extend the region to be written back to include subsequent contiguously
- * dirty pages if possible, but don't sleep while doing so.
- */
-static void cifs_extend_writeback(struct address_space *mapping,
- long *_count,
- loff_t start,
- int max_pages,
- size_t max_len,
- unsigned int *_len)
-{
- struct folio_batch batch;
- struct folio *folio;
- unsigned int psize, nr_pages;
- size_t len = *_len;
- pgoff_t index = (start + len) / PAGE_SIZE;
- bool stop = true;
- unsigned int i;
- XA_STATE(xas, &mapping->i_pages, index);
-
- folio_batch_init(&batch);
-
- do {
- /* Firstly, we gather up a batch of contiguous dirty pages
- * under the RCU read lock - but we can't clear the dirty flags
- * there if any of those pages are mapped.
- */
- rcu_read_lock();
-
- xas_for_each(&xas, folio, ULONG_MAX) {
- stop = true;
- if (xas_retry(&xas, folio))
- continue;
- if (xa_is_value(folio))
- break;
- if (folio_index(folio) != index)
- break;
- if (!folio_try_get_rcu(folio)) {
- xas_reset(&xas);
- continue;
- }
- nr_pages = folio_nr_pages(folio);
- if (nr_pages > max_pages)
- break;
-
- /* Has the page moved or been split? */
- if (unlikely(folio != xas_reload(&xas))) {
- folio_put(folio);
- break;
- }
-
- if (!folio_trylock(folio)) {
- folio_put(folio);
- break;
- }
- if (!folio_test_dirty(folio) || folio_test_writeback(folio)) {
- folio_unlock(folio);
- folio_put(folio);
- break;
- }
-
- psize = folio_size(folio);
- len += psize;
- stop = false;
- if (max_pages <= 0 || len >= max_len || *_count <= 0)
- stop = true;
-
- index += nr_pages;
- if (!folio_batch_add(&batch, folio))
- break;
- if (stop)
- break;
- }
-
- if (!stop)
- xas_pause(&xas);
- rcu_read_unlock();
-
- /* Now, if we obtained any pages, we can shift them to being
- * writable and mark them for caching.
- */
- if (!folio_batch_count(&batch))
- break;
-
- for (i = 0; i < folio_batch_count(&batch); i++) {
- folio = batch.folios[i];
- /* The folio should be locked, dirty and not undergoing
- * writeback from the loop above.
- */
- if (!folio_clear_dirty_for_io(folio))
- WARN_ON(1);
- if (folio_start_writeback(folio))
- WARN_ON(1);
-
- *_count -= folio_nr_pages(folio);
- folio_unlock(folio);
- }
-
- folio_batch_release(&batch);
- cond_resched();
- } while (!stop);
-
- *_len = len;
-}
+struct cifs_writepages_context {
+ struct cifs_writedata *wdata;
+ struct TCP_Server_Info *server;
+ struct cifs_credits credits;
+ unsigned long long start;
+ size_t len;
+ size_t wsize;
+ unsigned int xid;
+ bool begun;
+ bool caching;
+};
/*
- * Write back the locked page and any subsequent non-locked dirty pages.
+ * Set up a writeback op.
*/
-static ssize_t cifs_write_back_from_locked_folio(struct address_space *mapping,
- struct writeback_control *wbc,
- struct folio *folio,
- loff_t start, loff_t end)
+static int cifs_writeback_begin(struct address_space *mapping,
+ struct writeback_control *wbc,
+ unsigned long long start,
+ struct cifs_writepages_context *ctx)
{
struct inode *inode = mapping->host;
struct TCP_Server_Info *server;
struct cifs_writedata *wdata;
struct cifs_sb_info *cifs_sb = CIFS_SB(inode->i_sb);
- struct cifs_credits credits_on_stack;
- struct cifs_credits *credits = &credits_on_stack;
struct cifsFileInfo *cfile = NULL;
- unsigned int xid, wsize, len;
- loff_t i_size = i_size_read(inode);
- size_t max_len;
- long count = wbc->nr_to_write;
+ unsigned int wsize, len;
int rc;
- /* The folio should be locked, dirty and not undergoing writeback. */
- if (folio_start_writeback(folio))
- WARN_ON(1);
-
- count -= folio_nr_pages(folio);
- len = folio_size(folio);
-
- xid = get_xid();
+ ctx->xid = get_xid();
server = cifs_pick_channel(cifs_sb_master_tcon(cifs_sb)->ses);
rc = cifs_get_writable_file(CIFS_I(inode), FIND_WR_ANY, &cfile);
@@ -2756,7 +2651,7 @@ static ssize_t cifs_write_back_from_locked_folio(struct address_space *mapping,
}
rc = server->ops->wait_mtu_credits(server, cifs_sb->ctx->wsize,
- &wsize, credits);
+ &wsize, &ctx->credits);
if (rc != 0)
goto err_close;
@@ -2767,56 +2662,60 @@ static ssize_t cifs_write_back_from_locked_folio(struct address_space *mapping,
}
wdata->sync_mode = wbc->sync_mode;
- wdata->offset = folio_pos(folio);
+ wdata->offset = start;
wdata->pid = cfile->pid;
- wdata->credits = credits_on_stack;
+ wdata->credits = ctx->credits;
wdata->cfile = cfile;
wdata->server = server;
- cfile = NULL;
-
- /* Find all consecutive lockable dirty pages, stopping when we find a
- * page that is not immediately lockable, is not dirty or is missing,
- * or we reach the end of the range.
- */
- if (start < i_size) {
- /* Trim the write to the EOF; the extra data is ignored. Also
- * put an upper limit on the size of a single storedata op.
- */
- max_len = wsize;
- max_len = min_t(unsigned long long, max_len, end - start + 1);
- max_len = min_t(unsigned long long, max_len, i_size - start);
-
- if (len < max_len) {
- int max_pages = INT_MAX;
-
-#ifdef CONFIG_CIFS_SMB_DIRECT
- if (server->smbd_conn)
- max_pages = server->smbd_conn->max_frmr_depth;
-#endif
- max_pages -= folio_nr_pages(folio);
+ ctx->wsize = wsize;
+ ctx->server = server;
+ ctx->wdata = wdata;
+ ctx->begun = true;
+ return 0;
- if (max_pages > 0)
- cifs_extend_writeback(mapping, &count, start,
- max_pages, max_len, &len);
- }
- len = min_t(loff_t, len, max_len);
+err_uncredit:
+ add_credits_and_wake_if(server, &ctx->credits, 0);
+err_close:
+ if (cfile)
+ cifsFileInfo_put(cfile);
+err_xid:
+ free_xid(ctx->xid);
+ if (is_retryable_error(rc)) {
+ cifs_pages_write_redirty(inode, start, len);
+ } else {
+ cifs_pages_write_failed(inode, start, len);
+ mapping_set_error(mapping, rc);
}
+ /* Indication to update ctime and mtime as close is deferred */
+ set_bit(CIFS_INO_MODIFIED_ATTR, &CIFS_I(inode)->flags);
+ return rc;
+}
- wdata->bytes = len;
+/*
+ * Flush a block of pages to the server and the cache.
+ */
+static int cifs_writepages_submit(struct address_space *mapping,
+ struct writeback_control *wbc,
+ struct cifs_writepages_context *ctx)
+{
+ struct TCP_Server_Info *server = ctx->server;
+ struct cifs_writedata *wdata = ctx->wdata;
+ unsigned long long i_size = i_size_read(mapping->host);
+ int rc;
- /* We now have a contiguous set of dirty pages, each with writeback
- * set; the first page is still locked at this point, but all the rest
- * have been unlocked.
+ /* We now have a contiguous set of dirty pages, each with
+ * writeback set.
*/
- folio_unlock(folio);
-
- if (start < i_size) {
- iov_iter_xarray(&wdata->iter, ITER_SOURCE, &mapping->i_pages,
- start, len);
+ if (ctx->start < i_size) {
+ if (ctx->len > i_size - ctx->start)
+ ctx->len = i_size - ctx->start;
+ wdata->bytes = ctx->len;
+ iov_iter_xarray(&wdata->iter, ITER_SOURCE,
+ &mapping->i_pages, ctx->start, wdata->bytes);
rc = adjust_credits(wdata->server, &wdata->credits, wdata->bytes);
if (rc)
- goto err_wdata;
+ goto err;
if (wdata->cfile->invalidHandle)
rc = -EAGAIN;
@@ -2827,133 +2726,79 @@ static ssize_t cifs_write_back_from_locked_folio(struct address_space *mapping,
kref_put(&wdata->refcount, cifs_writedata_release);
goto err_close;
}
+
} else {
/* The dirty region was entirely beyond the EOF. */
- cifs_pages_written_back(inode, start, len);
+ cifs_pages_written_back(mapping->host, ctx->start, ctx->len);
rc = 0;
}
-err_wdata:
+err:
kref_put(&wdata->refcount, cifs_writedata_release);
-err_uncredit:
- add_credits_and_wake_if(server, credits, 0);
+ add_credits_and_wake_if(server, &ctx->credits, 0);
err_close:
- if (cfile)
- cifsFileInfo_put(cfile);
-err_xid:
- free_xid(xid);
+ free_xid(ctx->xid);
if (rc == 0) {
- wbc->nr_to_write = count;
- rc = len;
+ rc = 0;
} else if (is_retryable_error(rc)) {
- cifs_pages_write_redirty(inode, start, len);
+ cifs_pages_write_redirty(mapping->host, ctx->start, ctx->len);
} else {
- cifs_pages_write_failed(inode, start, len);
+ cifs_pages_write_failed(mapping->host, ctx->start, ctx->len);
mapping_set_error(mapping, rc);
}
+
/* Indication to update ctime and mtime as close is deferred */
- set_bit(CIFS_INO_MODIFIED_ATTR, &CIFS_I(inode)->flags);
+ set_bit(CIFS_INO_MODIFIED_ATTR, &CIFS_I(mapping->host)->flags);
+ ctx->wdata = NULL;
+ ctx->begun = false;
return rc;
}
/*
- * write a region of pages back to the server
+ * Add a page to the set and flush when large enough.
*/
-static int cifs_writepages_region(struct address_space *mapping,
- struct writeback_control *wbc,
- loff_t start, loff_t end, loff_t *_next)
+static int cifs_writepages_add_folio(struct folio *folio,
+ struct writeback_control *wbc, void *data)
{
- struct folio_batch fbatch;
- int skips = 0;
-
- folio_batch_init(&fbatch);
- do {
- int nr;
- pgoff_t index = start / PAGE_SIZE;
-
- nr = filemap_get_folios_tag(mapping, &index, end / PAGE_SIZE,
- PAGECACHE_TAG_DIRTY, &fbatch);
- if (!nr)
- break;
-
- for (int i = 0; i < nr; i++) {
- ssize_t ret;
- struct folio *folio = fbatch.folios[i];
-
-redo_folio:
- start = folio_pos(folio); /* May regress with THPs */
-
- /* At this point we hold neither the i_pages lock nor the
- * page lock: the page may be truncated or invalidated
- * (changing page->mapping to NULL), or even swizzled
- * back from swapper_space to tmpfs file mapping
- */
- if (wbc->sync_mode != WB_SYNC_NONE) {
- ret = folio_lock_killable(folio);
- if (ret < 0)
- goto write_error;
- } else {
- if (!folio_trylock(folio))
- goto skip_write;
- }
-
- if (folio_mapping(folio) != mapping ||
- !folio_test_dirty(folio)) {
- start += folio_size(folio);
- folio_unlock(folio);
- continue;
- }
-
- if (folio_test_writeback(folio) ||
- folio_test_fscache(folio)) {
- folio_unlock(folio);
- if (wbc->sync_mode == WB_SYNC_NONE)
- goto skip_write;
-
- folio_wait_writeback(folio);
-#ifdef CONFIG_CIFS_FSCACHE
- folio_wait_fscache(folio);
-#endif
- goto redo_folio;
- }
-
- if (!folio_clear_dirty_for_io(folio))
- /* We hold the page lock - it should've been dirty. */
- WARN_ON(1);
+ struct cifs_writepages_context *ctx = data;
+ unsigned long long i_size = i_size_read(folio->mapping->host);
+ unsigned long long pos = folio_pos(folio);
+ size_t size = folio_size(folio);
+ int ret;
- ret = cifs_write_back_from_locked_folio(mapping, wbc, folio, start, end);
- if (ret < 0)
- goto write_error;
+ if (pos < i_size && size > i_size - pos)
+ size = i_size - pos;
- start += ret;
- continue;
-
-write_error:
- folio_batch_release(&fbatch);
- *_next = start;
+ if (ctx->begun) {
+ if (pos == ctx->start + ctx->len &&
+ ctx->len + size <= ctx->wsize)
+ goto add;
+ ret = cifs_writepages_submit(folio->mapping, wbc, ctx);
+ if (ret < 0) {
+ ctx->begun = false;
return ret;
+ }
+ }
-skip_write:
- /*
- * Too many skipped writes, or need to reschedule?
- * Treat it as a write error without an error code.
- */
- if (skips >= 5 || need_resched()) {
- ret = 0;
- goto write_error;
- }
+ ret = cifs_writeback_begin(folio->mapping, wbc, pos, ctx);
+ if (ret < 0)
+ return ret;
- /* Otherwise, just skip that folio and go on to the next */
- skips++;
- start += folio_size(folio);
- continue;
- }
+ ctx->start = folio_pos(folio);
+ ctx->len = 0;
+add:
+ ctx->len += folio_size(folio);
- folio_batch_release(&fbatch);
- cond_resched();
- } while (wbc->nr_to_write > 0);
+ folio_wait_fscache(folio);
+ folio_start_writeback(folio);
+ folio_unlock(folio);
- *_next = start;
+ if (ctx->len >= ctx->wsize) {
+ ret = cifs_writepages_submit(folio->mapping, wbc, ctx);
+ if (ret < 0)
+ return ret;
+ ctx->begun = false;
+ }
return 0;
}
@@ -2963,7 +2808,7 @@ static int cifs_writepages_region(struct address_space *mapping,
static int cifs_writepages(struct address_space *mapping,
struct writeback_control *wbc)
{
- loff_t start, next;
+ struct cifs_writepages_context ctx = {};
int ret;
/* We have to be careful as we can end up racing with setattr()
@@ -2971,26 +2816,11 @@ static int cifs_writepages(struct address_space *mapping,
* to prevent it.
*/
- if (wbc->range_cyclic) {
- start = mapping->writeback_index * PAGE_SIZE;
- ret = cifs_writepages_region(mapping, wbc, start, LLONG_MAX, &next);
- if (ret == 0) {
- mapping->writeback_index = next / PAGE_SIZE;
- if (start > 0 && wbc->nr_to_write > 0) {
- ret = cifs_writepages_region(mapping, wbc, 0,
- start, &next);
- if (ret == 0)
- mapping->writeback_index =
- next / PAGE_SIZE;
- }
- }
- } else if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) {
- ret = cifs_writepages_region(mapping, wbc, 0, LLONG_MAX, &next);
- if (wbc->nr_to_write > 0 && ret == 0)
- mapping->writeback_index = next / PAGE_SIZE;
- } else {
- ret = cifs_writepages_region(mapping, wbc,
- wbc->range_start, wbc->range_end, &next);
+ ret = write_cache_pages(mapping, wbc, cifs_writepages_add_folio, &ctx);
+ if (ret >= 0 && ctx.begun) {
+ ret = cifs_writepages_submit(mapping, wbc, &ctx);
+ if (ret < 0)
+ return ret;
}
return ret;
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