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Message-ID: <166902976709.269117.16991162776475572981.stgit@warthog.procyon.org.uk>
Date: Mon, 21 Nov 2022 11:22:47 +0000
From: David Howells <dhowells@...hat.com>
To: linux-afs@...ts.infradead.org
Cc: Marc Dionne <marc.dionne@...istor.com>,
Christoph Hellwig <hch@....de>,
Matthew Wilcox <willy@...radead.org>, dhowells@...hat.com,
linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [RFC PATCH v2] afs: Stop implementing ->writepage()
We're trying to get rid of the ->writepage() hook[1]. Stop afs from using
it by unlocking the page and calling afs_writepages_region() rather than
folio_write_one().
A flag is passed to afs_writepages_region() to indicate that it should only
write a single region so that we don't flush the entire file in
->write_begin(), but do add other dirty data to the region being written to
try and reduce the number of RPC ops.
This requires ->migrate_folio() to be implemented, so point that at
filemap_migrate_folio() for files and also for symlinks and directories.
This can be tested by turning on the afs_folio_dirty tracepoint and then
doing something like:
xfs_io -c "w 2223 7000" -c "w 15000 22222" -c "w 23 7" /afs/my/test/foo
and then looking in the trace to see if the write at position 15000 gets
stored before page 0 gets dirtied for the write at position 23.
Signed-off-by: David Howells <dhowells@...hat.com>
cc: Marc Dionne <marc.dionne@...istor.com>
cc: Christoph Hellwig <hch@....de>
cc: Matthew Wilcox <willy@...radead.org>
cc: linux-afs@...ts.infradead.org
Link: https://lore.kernel.org/r/20221113162902.883850-1-hch@lst.de/ [1]
Link: https://lore.kernel.org/r/166876785552.222254.4403222906022558715.stgit@warthog.procyon.org.uk/ # v1
---
fs/afs/dir.c | 1 +
fs/afs/file.c | 3 +-
fs/afs/write.c | 83 ++++++++++++++++++++++++++++++++------------------------
3 files changed, 50 insertions(+), 37 deletions(-)
diff --git a/fs/afs/dir.c b/fs/afs/dir.c
index 230c2d19116d..baed7b095087 100644
--- a/fs/afs/dir.c
+++ b/fs/afs/dir.c
@@ -77,6 +77,7 @@ const struct address_space_operations afs_dir_aops = {
.dirty_folio = afs_dir_dirty_folio,
.release_folio = afs_dir_release_folio,
.invalidate_folio = afs_dir_invalidate_folio,
+ .migrate_folio = filemap_migrate_folio,
};
const struct dentry_operations afs_fs_dentry_operations = {
diff --git a/fs/afs/file.c b/fs/afs/file.c
index d1cfb235c4b9..a2325e0b9d38 100644
--- a/fs/afs/file.c
+++ b/fs/afs/file.c
@@ -58,14 +58,15 @@ const struct address_space_operations afs_file_aops = {
.invalidate_folio = afs_invalidate_folio,
.write_begin = afs_write_begin,
.write_end = afs_write_end,
- .writepage = afs_writepage,
.writepages = afs_writepages,
+ .migrate_folio = filemap_migrate_folio,
};
const struct address_space_operations afs_symlink_aops = {
.read_folio = afs_symlink_read_folio,
.release_folio = afs_release_folio,
.invalidate_folio = afs_invalidate_folio,
+ .migrate_folio = filemap_migrate_folio,
};
static const struct vm_operations_struct afs_vm_ops = {
diff --git a/fs/afs/write.c b/fs/afs/write.c
index 9ebdd36eaf2f..197753181116 100644
--- a/fs/afs/write.c
+++ b/fs/afs/write.c
@@ -14,6 +14,11 @@
#include <linux/netfs.h>
#include "internal.h"
+static int afs_writepages_region(struct address_space *mapping,
+ struct writeback_control *wbc,
+ loff_t start, loff_t end, loff_t *_next,
+ bool max_one_loop);
+
static void afs_write_to_cache(struct afs_vnode *vnode, loff_t start, size_t len,
loff_t i_size, bool caching);
@@ -38,6 +43,25 @@ static void afs_folio_start_fscache(bool caching, struct folio *folio)
}
#endif
+/*
+ * Flush out a conflicting write. This may extend the write to the surrounding
+ * pages if also dirty and contiguous to the conflicting region..
+ */
+static int afs_flush_conflicting_write(struct address_space *mapping,
+ struct folio *folio)
+{
+ struct writeback_control wbc = {
+ .sync_mode = WB_SYNC_ALL,
+ .nr_to_write = LONG_MAX,
+ .range_start = folio_pos(folio),
+ .range_end = LLONG_MAX,
+ };
+ loff_t next;
+
+ return afs_writepages_region(mapping, &wbc, folio_pos(folio), LLONG_MAX,
+ &next, true);
+}
+
/*
* prepare to perform part of a write to a page
*/
@@ -80,7 +104,8 @@ int afs_write_begin(struct file *file, struct address_space *mapping,
if (folio_test_writeback(folio)) {
trace_afs_folio_dirty(vnode, tracepoint_string("alrdy"), folio);
- goto flush_conflicting_write;
+ folio_unlock(folio);
+ goto wait_for_writeback;
}
/* If the file is being filled locally, allow inter-write
* spaces to be merged into writes. If it's not, only write
@@ -99,8 +124,15 @@ int afs_write_begin(struct file *file, struct address_space *mapping,
* flush the page out.
*/
flush_conflicting_write:
- _debug("flush conflict");
- ret = folio_write_one(folio);
+ trace_afs_folio_dirty(vnode, tracepoint_string("confl"), folio);
+ folio_unlock(folio);
+
+ ret = afs_flush_conflicting_write(mapping, folio);
+ if (ret < 0)
+ goto error;
+
+wait_for_writeback:
+ ret = folio_wait_writeback_killable(folio);
if (ret < 0)
goto error;
@@ -663,40 +695,13 @@ static ssize_t afs_write_back_from_locked_folio(struct address_space *mapping,
return ret;
}
-/*
- * write a page back to the server
- * - the caller locked the page for us
- */
-int afs_writepage(struct page *subpage, struct writeback_control *wbc)
-{
- struct folio *folio = page_folio(subpage);
- ssize_t ret;
- loff_t start;
-
- _enter("{%lx},", folio_index(folio));
-
-#ifdef CONFIG_AFS_FSCACHE
- folio_wait_fscache(folio);
-#endif
-
- start = folio_index(folio) * PAGE_SIZE;
- ret = afs_write_back_from_locked_folio(folio_mapping(folio), wbc,
- folio, start, LLONG_MAX - start);
- if (ret < 0) {
- _leave(" = %zd", ret);
- return ret;
- }
-
- _leave(" = 0");
- return 0;
-}
-
/*
* write a region of pages back to the server
*/
static int afs_writepages_region(struct address_space *mapping,
struct writeback_control *wbc,
- loff_t start, loff_t end, loff_t *_next)
+ loff_t start, loff_t end, loff_t *_next,
+ bool max_one_loop)
{
struct folio *folio;
struct page *head_page;
@@ -775,6 +780,9 @@ static int afs_writepages_region(struct address_space *mapping,
start += ret;
+ if (max_one_loop)
+ break;
+
cond_resched();
} while (wbc->nr_to_write > 0);
@@ -806,24 +814,27 @@ int afs_writepages(struct address_space *mapping,
if (wbc->range_cyclic) {
start = mapping->writeback_index * PAGE_SIZE;
- ret = afs_writepages_region(mapping, wbc, start, LLONG_MAX, &next);
+ ret = afs_writepages_region(mapping, wbc, start, LLONG_MAX,
+ &next, false);
if (ret == 0) {
mapping->writeback_index = next / PAGE_SIZE;
if (start > 0 && wbc->nr_to_write > 0) {
ret = afs_writepages_region(mapping, wbc, 0,
- start, &next);
+ start, &next, false);
if (ret == 0)
mapping->writeback_index =
next / PAGE_SIZE;
}
}
} else if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX) {
- ret = afs_writepages_region(mapping, wbc, 0, LLONG_MAX, &next);
+ ret = afs_writepages_region(mapping, wbc, 0, LLONG_MAX,
+ &next, false);
if (wbc->nr_to_write > 0 && ret == 0)
mapping->writeback_index = next / PAGE_SIZE;
} else {
ret = afs_writepages_region(mapping, wbc,
- wbc->range_start, wbc->range_end, &next);
+ wbc->range_start, wbc->range_end,
+ &next, false);
}
up_read(&vnode->validate_lock);
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