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Subject[PATCH 01/12] buffer: have alloc_page_buffers() use __GFP_NOFAIL
Date
Instead of adding weird retry logic in that function, utilize
__GFP_NOFAIL to ensure that the vm takes care of handling any
potential retries appropriately. This means we don't have to
call free_more_memory() from here.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
---
drivers/md/bitmap.c | 2 +-
fs/buffer.c | 33 ++++++++++-----------------------
fs/ntfs/aops.c | 2 +-
fs/ntfs/mft.c | 2 +-
include/linux/buffer_head.h | 2 +-
5 files changed, 14 insertions(+), 27 deletions(-)

diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index d2121637b4ab..4d8ed74efadf 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -368,7 +368,7 @@ static int read_page(struct file *file, unsigned long index,
pr_debug("read bitmap file (%dB @ %llu)\n", (int)PAGE_SIZE,
(unsigned long long)index << PAGE_SHIFT);

- bh = alloc_page_buffers(page, 1<<inode->i_blkbits, 0);
+ bh = alloc_page_buffers(page, 1<<inode->i_blkbits, false);
if (!bh) {
ret = -ENOMEM;
goto out;
diff --git a/fs/buffer.c b/fs/buffer.c
index 170df856bdb9..1234ae343aef 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -861,16 +861,19 @@ int remove_inode_buffers(struct inode *inode)
* which may not fail from ordinary buffer allocations.
*/
struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
- int retry)
+ bool retry)
{
struct buffer_head *bh, *head;
+ gfp_t gfp = GFP_NOFS;
long offset;

-try_again:
+ if (retry)
+ gfp |= __GFP_NOFAIL;
+
head = NULL;
offset = PAGE_SIZE;
while ((offset -= size) >= 0) {
- bh = alloc_buffer_head(GFP_NOFS);
+ bh = alloc_buffer_head(gfp);
if (!bh)
goto no_grow;

@@ -896,23 +899,7 @@ struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
} while (head);
}

- /*
- * Return failure for non-async IO requests. Async IO requests
- * are not allowed to fail, so we have to wait until buffer heads
- * become available. But we don't want tasks sleeping with
- * partially complete buffers, so all were released above.
- */
- if (!retry)
- return NULL;
-
- /* We're _really_ low on memory. Now we just
- * wait for old buffer heads to become free due to
- * finishing IO. Since this is an async request and
- * the reserve list is empty, we're sure there are
- * async buffer heads in use.
- */
- free_more_memory();
- goto try_again;
+ return NULL;
}
EXPORT_SYMBOL_GPL(alloc_page_buffers);

@@ -1021,7 +1008,7 @@ grow_dev_page(struct block_device *bdev, sector_t block,
/*
* Allocate some buffers for this page
*/
- bh = alloc_page_buffers(page, size, 0);
+ bh = alloc_page_buffers(page, size, false);
if (!bh)
goto failed;

@@ -1575,7 +1562,7 @@ void create_empty_buffers(struct page *page,
{
struct buffer_head *bh, *head, *tail;

- head = alloc_page_buffers(page, blocksize, 1);
+ head = alloc_page_buffers(page, blocksize, true);
bh = head;
do {
bh->b_state |= b_state;
@@ -2638,7 +2625,7 @@ int nobh_write_begin(struct address_space *mapping,
* Be careful: the buffer linked list is a NULL terminated one, rather
* than the circular one we're used to.
*/
- head = alloc_page_buffers(page, blocksize, 0);
+ head = alloc_page_buffers(page, blocksize, false);
if (!head) {
ret = -ENOMEM;
goto out_release;
diff --git a/fs/ntfs/aops.c b/fs/ntfs/aops.c
index cc91856b5e2d..3a2e509c77c5 100644
--- a/fs/ntfs/aops.c
+++ b/fs/ntfs/aops.c
@@ -1739,7 +1739,7 @@ void mark_ntfs_record_dirty(struct page *page, const unsigned int ofs) {
spin_lock(&mapping->private_lock);
if (unlikely(!page_has_buffers(page))) {
spin_unlock(&mapping->private_lock);
- bh = head = alloc_page_buffers(page, bh_size, 1);
+ bh = head = alloc_page_buffers(page, bh_size, true);
spin_lock(&mapping->private_lock);
if (likely(!page_has_buffers(page))) {
struct buffer_head *tail;
diff --git a/fs/ntfs/mft.c b/fs/ntfs/mft.c
index b6f402194f02..ee8392aee9f6 100644
--- a/fs/ntfs/mft.c
+++ b/fs/ntfs/mft.c
@@ -507,7 +507,7 @@ int ntfs_sync_mft_mirror(ntfs_volume *vol, const unsigned long mft_no,
if (unlikely(!page_has_buffers(page))) {
struct buffer_head *tail;

- bh = head = alloc_page_buffers(page, blocksize, 1);
+ bh = head = alloc_page_buffers(page, blocksize, true);
do {
set_buffer_uptodate(bh);
tail = bh;
diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index c8dae555eccf..ae2d25f01b98 100644
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -156,7 +156,7 @@ void set_bh_page(struct buffer_head *bh,
struct page *page, unsigned long offset);
int try_to_free_buffers(struct page *);
struct buffer_head *alloc_page_buffers(struct page *page, unsigned long size,
- int retry);
+ bool retry);
void create_empty_buffers(struct page *, unsigned long,
unsigned long b_state);
void end_buffer_read_sync(struct buffer_head *bh, int uptodate);
--
2.7.4
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