[PATCH v2 07/12] btrfs: make prepare_pages nowait compatible

Stefan Roesch
2022-09-08T00:26:52Z

Add nowait parameter to the prepare_pages function. In case nowait is
specified for an async buffered write request, do a nowait allocation or
return -EAGAIN.

Signed-off-by: Stefan Roesch <shr@fb.com>
---
fs/btrfs/file.c | 43 ++++++++++++++++++++++++++++++++++++-------
1 file changed, 36 insertions(+), 7 deletions(-)

diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index cf19d381ead6..a154a3cec44b 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -1339,26 +1339,55 @@ static int prepare_uptodate_page(struct inode *inode,
return 0;
}

+static int get_prepare_fgp_flags(bool nowait)
+{
+ int fgp_flags;
+
+ fgp_flags = FGP_LOCK|FGP_ACCESSED|FGP_CREAT;
+ if (nowait)
+ fgp_flags |= FGP_NOWAIT;
+
+ return fgp_flags;
+}
+
+static gfp_t get_prepare_gfp_flags(struct inode *inode, bool nowait)
+{
+ gfp_t gfp;
+
+ gfp = btrfs_alloc_write_mask(inode->i_mapping);
+ if (nowait) {
+ gfp &= ~__GFP_DIRECT_RECLAIM;
+ gfp |= GFP_NOWAIT;
+ }
+
+ return gfp;
+}
+
/*
* this just gets pages into the page cache and locks them down.
*/
static noinline int prepare_pages(struct inode *inode, struct page **pages,
size_t num_pages, loff_t pos,
- size_t write_bytes, bool force_uptodate)
+ size_t write_bytes, bool force_uptodate,
+ bool nowait)
{
int i;
unsigned long index = pos >> PAGE_SHIFT;
- gfp_t mask = btrfs_alloc_write_mask(inode->i_mapping);
+ gfp_t mask = get_prepare_gfp_flags(inode, nowait);
+ int fgp_flags = get_prepare_fgp_flags(nowait);
int err = 0;
int faili;

for (i = 0; i < num_pages; i++) {
again:
- pages[i] = find_or_create_page(inode->i_mapping, index + i,
- mask | __GFP_WRITE);
+ pages[i] = pagecache_get_page(inode->i_mapping, index + i,
+ fgp_flags, mask | __GFP_WRITE);
if (!pages[i]) {
faili = i - 1;
- err = -ENOMEM;
+ if (nowait)
+ err = -EAGAIN;
+ else
+ err = -ENOMEM;
goto fail;
}

@@ -1376,7 +1405,7 @@ static noinline int prepare_pages(struct inode *inode, struct page **pages,
pos + write_bytes, false);
if (err) {
put_page(pages[i]);
- if (err == -EAGAIN) {
+ if (!nowait && err == -EAGAIN) {
err = 0;
goto again;
}
@@ -1716,7 +1745,7 @@ static noinline ssize_t btrfs_buffered_write(struct kiocb *iocb,
*/
ret = prepare_pages(inode, pages, num_pages,
pos, write_bytes,
- force_page_uptodate);
+ force_page_uptodate, false);
if (ret) {
btrfs_delalloc_release_extents(BTRFS_I(inode),
reserve_bytes);
--
2.30.2