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ext4: bio_alloc with __GFP_DIRECT_RECLAIM never fails

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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@mit.edu>
Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Ritesh Harjani <riteshh@linux.ibm.com>
Reviewed-by: Chao Yu <yuchao0@huawei.com>
Signed-off-by: Gao Xiang <gaoxiang25@huawei.com>
Link: https://lore.kernel.org/r/20191031092315.139267-1-gaoxiang25@huawei.com
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
This commit is contained in:
Gao Xiang 2019-10-31 17:23:15 +08:00 committed by Theodore Ts'o
parent ebc11f7b1f
commit 5500221ea1
2 changed files with 26 additions and 37 deletions
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57
fs/ext4/page-io.c
View File

@ -394,14 +394,16 @@ 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;
@ -409,13 +411,12 @@ 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;
@ -424,9 +425,7 @@ 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));
@ -434,7 +433,6 @@ 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,
@ -527,8 +525,14 @@ 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;
}
}
@ -536,30 +540,13 @@ 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)

6
fs/ext4/readpage.c
View File

@ -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);