[PATCH 4/6] EXT4: remove congestion_wait from ext4_bio_write_page, and simplify

NeilBrown
2021-09-14T00:28:34Z

congestion_wait() is indistinguishable from
schedule_timeout_uninterruptible(). It is best avoided and should be
deprecated.

It is not needed in ext4_bio_write_page(). There are two cases.
If there are no ->io_bio yet, then it is appropriate to use __GFP_NOFAIL
which does the waiting in a better place. The code already uses this
flag on the second attempt. This patch changes to it always use that
flag for this case.

If there *are* ->io_bio (in which case the allocation was non-blocking)
we submit the io and return the first case. No waiting is needed in
this case.

So remove the congestion_wait() call, and simplify the code so that the
two cases are somewhat clearer.

Remove the "if (io->io_bio)" before calling ext4_io_submit() as that
test is performed internally by that function.

Signed-off-by: NeilBrown <neilb@suse.de>
---
fs/ext4/page-io.c | 13 +++++--------
1 file changed, 5 insertions(+), 8 deletions(-)

diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
index f038d578d8d8..3b6ece0d3ad6 100644
--- a/fs/ext4/page-io.c
+++ b/fs/ext4/page-io.c
@@ -506,7 +506,7 @@ int ext4_bio_write_page(struct ext4_io_submit *io,
* can't happen in the common case of blocksize == PAGE_SIZE.
*/
if (fscrypt_inode_uses_fs_layer_crypto(inode) && nr_to_submit) {
- gfp_t gfp_flags = GFP_NOFS;
+ gfp_t gfp_flags;
unsigned int enc_bytes = round_up(len, i_blocksize(inode));

/*
@@ -514,21 +514,18 @@ int ext4_bio_write_page(struct ext4_io_submit *io,
* a waiting mask (i.e. request guaranteed allocation) on the
* first page of the bio. Otherwise it can deadlock.
*/
+ retry_encrypt:
if (io->io_bio)
gfp_flags = GFP_NOWAIT | __GFP_NOWARN;
- retry_encrypt:
+ else
+ gfp_flags = GFP_NOFS | __GFP_NOFAIL;
bounce_page = fscrypt_encrypt_pagecache_blocks(page, enc_bytes,
0, gfp_flags);
if (IS_ERR(bounce_page)) {
ret = PTR_ERR(bounce_page);
if (ret == -ENOMEM &&
(io->io_bio || wbc->sync_mode == WB_SYNC_ALL)) {
- gfp_flags = GFP_NOFS;
- if (io->io_bio)
- ext4_io_submit(io);
- else
- gfp_flags |= __GFP_NOFAIL;
- congestion_wait(BLK_RW_ASYNC, HZ/50);
+ ext4_io_submit(io);
goto retry_encrypt;
}