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Date: Thu, 31 Oct 2019 17:23:15 +0800
From: Gao Xiang <gaoxiang25@...wei.com>
To: Theodore Ts'o <tytso@....edu>,
Andreas Dilger <adilger.kernel@...ger.ca>
CC: <linux-ext4@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
Gao Xiang <gaoxiang25@...wei.com>,
Ritesh Harjani <riteshh@...ux.ibm.com>,
Chao Yu <yuchao0@...wei.com>
Subject: [PATCH v2] ext4: bio_alloc with __GFP_DIRECT_RECLAIM never fails
Similar to [1] [2], bio_alloc with __GFP_DIRECT_RECLAIM flags
guarantees bio allocation under some given restrictions, as
stated in block/bio.c and fs/direct-io.c So here it's ok to
not check for NULL value from bio_alloc().
[1] https://lore.kernel.org/r/20191030035518.65477-1-gaoxiang25@huawei.com
[2] https://lore.kernel.org/r/20190830162812.GA10694@infradead.org
Cc: Theodore Ts'o <tytso@....edu>
Cc: Andreas Dilger <adilger.kernel@...ger.ca>
Cc: Ritesh Harjani <riteshh@...ux.ibm.com>
Cc: Chao Yu <yuchao0@...wei.com>
Signed-off-by: Gao Xiang <gaoxiang25@...wei.com>
---
changes since v1:
- fix commit message and simplify logic as suggested by Ritesh;
- add short messages ahead of bio_alloc suggested by Ted.
fs/ext4/page-io.c | 57 ++++++++++++++++++----------------------------
fs/ext4/readpage.c | 6 +++--
2 files changed, 26 insertions(+), 37 deletions(-)
diff --git a/fs/ext4/page-io.c b/fs/ext4/page-io.c
index 12ceadef32c5..c92504c1b1ca 100644
--- a/fs/ext4/page-io.c
+++ b/fs/ext4/page-io.c
@@ -358,14 +358,16 @@ void ext4_io_submit_init(struct ext4_io_submit *io,
io->io_end = NULL;
}
-static int io_submit_init_bio(struct ext4_io_submit *io,
- struct buffer_head *bh)
+static void io_submit_init_bio(struct ext4_io_submit *io,
+ struct buffer_head *bh)
{
struct bio *bio;
+ /*
+ * bio_alloc will _always_ be able to allocate a bio if
+ * __GFP_DIRECT_RECLAIM is set, see comments for bio_alloc_bioset().
+ */
bio = bio_alloc(GFP_NOIO, BIO_MAX_PAGES);
- if (!bio)
- return -ENOMEM;
bio->bi_iter.bi_sector = bh->b_blocknr * (bh->b_size >> 9);
bio_set_dev(bio, bh->b_bdev);
bio->bi_end_io = ext4_end_bio;
@@ -373,13 +375,12 @@ static int io_submit_init_bio(struct ext4_io_submit *io,
io->io_bio = bio;
io->io_next_block = bh->b_blocknr;
wbc_init_bio(io->io_wbc, bio);
- return 0;
}
-static int io_submit_add_bh(struct ext4_io_submit *io,
- struct inode *inode,
- struct page *page,
- struct buffer_head *bh)
+static void io_submit_add_bh(struct ext4_io_submit *io,
+ struct inode *inode,
+ struct page *page,
+ struct buffer_head *bh)
{
int ret;
@@ -388,9 +389,7 @@ static int io_submit_add_bh(struct ext4_io_submit *io,
ext4_io_submit(io);
}
if (io->io_bio == NULL) {
- ret = io_submit_init_bio(io, bh);
- if (ret)
- return ret;
+ io_submit_init_bio(io, bh);
io->io_bio->bi_write_hint = inode->i_write_hint;
}
ret = bio_add_page(io->io_bio, page, bh->b_size, bh_offset(bh));
@@ -398,7 +397,6 @@ static int io_submit_add_bh(struct ext4_io_submit *io,
goto submit_and_retry;
wbc_account_cgroup_owner(io->io_wbc, page, bh->b_size);
io->io_next_block++;
- return 0;
}
int ext4_bio_write_page(struct ext4_io_submit *io,
@@ -491,8 +489,14 @@ int ext4_bio_write_page(struct ext4_io_submit *io,
gfp_flags |= __GFP_NOFAIL;
goto retry_encrypt;
}
- bounce_page = NULL;
- goto out;
+
+ printk_ratelimited(KERN_ERR "%s: ret = %d\n", __func__, ret);
+ redirty_page_for_writepage(wbc, page);
+ do {
+ clear_buffer_async_write(bh);
+ bh = bh->b_this_page;
+ } while (bh != head);
+ goto unlock;
}
}
@@ -500,30 +504,13 @@ int ext4_bio_write_page(struct ext4_io_submit *io,
do {
if (!buffer_async_write(bh))
continue;
- ret = io_submit_add_bh(io, inode, bounce_page ?: page, bh);
- if (ret) {
- /*
- * We only get here on ENOMEM. Not much else
- * we can do but mark the page as dirty, and
- * better luck next time.
- */
- break;
- }
+ io_submit_add_bh(io, inode,
+ bounce_page ? bounce_page : page, bh);
nr_submitted++;
clear_buffer_dirty(bh);
} while ((bh = bh->b_this_page) != head);
- /* Error stopped previous loop? Clean up buffers... */
- if (ret) {
- out:
- fscrypt_free_bounce_page(bounce_page);
- printk_ratelimited(KERN_ERR "%s: ret = %d\n", __func__, ret);
- redirty_page_for_writepage(wbc, page);
- do {
- clear_buffer_async_write(bh);
- bh = bh->b_this_page;
- } while (bh != head);
- }
+unlock:
unlock_page(page);
/* Nothing submitted - we have to end page writeback */
if (!nr_submitted)
diff --git a/fs/ext4/readpage.c b/fs/ext4/readpage.c
index a30b203fa461..fef7755300c3 100644
--- a/fs/ext4/readpage.c
+++ b/fs/ext4/readpage.c
@@ -360,10 +360,12 @@ int ext4_mpage_readpages(struct address_space *mapping,
if (bio == NULL) {
struct bio_post_read_ctx *ctx;
+ /*
+ * bio_alloc will _always_ be able to allocate a bio if
+ * __GFP_DIRECT_RECLAIM is set, see bio_alloc_bioset().
+ */
bio = bio_alloc(GFP_KERNEL,
min_t(int, nr_pages, BIO_MAX_PAGES));
- if (!bio)
- goto set_error_page;
ctx = get_bio_post_read_ctx(inode, bio, page->index);
if (IS_ERR(ctx)) {
bio_put(bio);
--
2.17.1
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