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Commit 111ebb6e authored by OGAWA Hirofumi's avatar OGAWA Hirofumi Committed by Linus Torvalds
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[PATCH] writeback: fix range handling 



When a writeback_control's `start' and `end' fields are used to
indicate a one-byte-range starting at file offset zero, the required
values of .start=0,.end=0 mean that the ->writepages() implementation
has no way of telling that it is being asked to perform a range
request.  Because we're currently overloading (start == 0 && end == 0)
to mean "this is not a write-a-range request".

To make all this sane, the patch changes range of writeback_control.

So caller does: If it is calling ->writepages() to write pages, it
sets range (range_start/end or range_cyclic) always.

And if range_cyclic is true, ->writepages() thinks the range is
cyclic, otherwise it just uses range_start and range_end.

This patch does,

    - Add LLONG_MAX, LLONG_MIN, ULLONG_MAX to include/linux/kernel.h
      -1 is usually ok for range_end (type is long long). But, if someone did,

		range_end += val;		range_end is "val - 1"
		u64val = range_end >> bits;	u64val is "~(0ULL)"

      or something, they are wrong. So, this adds LLONG_MAX to avoid nasty
      things, and uses LLONG_MAX for range_end.

    - All callers of ->writepages() sets range_start/end or range_cyclic.

    - Fix updates of ->writeback_index. It seems already bit strange.
      If it starts at 0 and ended by check of nr_to_write, this last
      index may reduce chance to scan end of file.  So, this updates
      ->writeback_index only if range_cyclic is true or whole-file is
      scanned.

Signed-off-by: default avatarOGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: Nathan Scott <nathans@sgi.com>
Cc: Anton Altaparmakov <aia21@cantab.net>
Cc: Steven French <sfrench@us.ibm.com>
Cc: "Vladimir V. Saveliev" <vs@namesys.com>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 4c91c364

fs/cifs/file.c

+11 −13
Original line number Diff line number Diff line
@@ -1079,9 +1079,9 @@ static int cifs_writepages(struct address_space *mapping, 
	unsigned int bytes_written;

	struct cifs_sb_info *cifs_sb;

	int done = 0;

	pgoff_t end = -1;

	pgoff_t end;

	pgoff_t index;

	int is_range = 0;

 	int range_whole = 0;

	struct kvec iov[32];

	int len;

	int n_iov = 0;
@@ -1122,16 +1122,14 @@ static int cifs_writepages(struct address_space *mapping, 
	xid = GetXid();



	pagevec_init(&pvec, 0);

	if (wbc->sync_mode == WB_SYNC_NONE)

	if (wbc->range_cyclic) {

		index = mapping->writeback_index; /* Start from prev offset */

	else {

		index = 0;

		scanned = 1;

	}

	if (wbc->start || wbc->end) {

		index = wbc->start >> PAGE_CACHE_SHIFT;

		end = wbc->end >> PAGE_CACHE_SHIFT;

		is_range = 1;

		end = -1;

	} else {

		index = wbc->range_start >> PAGE_CACHE_SHIFT;

		end = wbc->range_end >> PAGE_CACHE_SHIFT;

		if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)

			range_whole = 1;

		scanned = 1;

	}

retry:
@@ -1167,7 +1165,7 @@ retry: 
				break;

			}



			if (unlikely(is_range) && (page->index > end)) {

			if (!wbc->range_cyclic && page->index > end) {

				done = 1;

				unlock_page(page);

				break;
@@ -1271,7 +1269,7 @@ retry: 
		index = 0;

		goto retry;

	}

	if (!is_range)

	if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))

		mapping->writeback_index = index;



	FreeXid(xid);

fs/fs-writeback.c

+4 −0
Original line number Diff line number Diff line
@@ -461,6 +461,8 @@ void sync_inodes_sb(struct super_block *sb, int wait) 
{

	struct writeback_control wbc = {

		.sync_mode	= wait ? WB_SYNC_ALL : WB_SYNC_HOLD,

		.range_start	= 0,

		.range_end	= LLONG_MAX,

	};

	unsigned long nr_dirty = read_page_state(nr_dirty);

	unsigned long nr_unstable = read_page_state(nr_unstable);
@@ -559,6 +561,8 @@ int write_inode_now(struct inode *inode, int sync) 
	struct writeback_control wbc = {

		.nr_to_write = LONG_MAX,

		.sync_mode = WB_SYNC_ALL,

		.range_start = 0,

		.range_end = LLONG_MAX,

	};



	if (!mapping_cap_writeback_dirty(inode->i_mapping))

fs/mpage.c

+10 −12
Original line number Diff line number Diff line
@@ -707,9 +707,9 @@ mpage_writepages(struct address_space *mapping, 
	struct pagevec pvec;

	int nr_pages;

	pgoff_t index;

	pgoff_t end = -1;		/* Inclusive */

	pgoff_t end;		/* Inclusive */

	int scanned = 0;

	int is_range = 0;

	int range_whole = 0;



	if (wbc->nonblocking && bdi_write_congested(bdi)) {

		wbc->encountered_congestion = 1;
@@ -721,16 +721,14 @@ mpage_writepages(struct address_space *mapping, 
		writepage = mapping->a_ops->writepage;



	pagevec_init(&pvec, 0);

	if (wbc->sync_mode == WB_SYNC_NONE) {

	if (wbc->range_cyclic) {

		index = mapping->writeback_index; /* Start from prev offset */

		end = -1;

	} else {

		index = 0;			  /* whole-file sweep */

		scanned = 1;

	}

	if (wbc->start || wbc->end) {

		index = wbc->start >> PAGE_CACHE_SHIFT;

		end = wbc->end >> PAGE_CACHE_SHIFT;

		is_range = 1;

		index = wbc->range_start >> PAGE_CACHE_SHIFT;

		end = wbc->range_end >> PAGE_CACHE_SHIFT;

		if (wbc->range_start == 0 && wbc->range_end == LLONG_MAX)

			range_whole = 1;

		scanned = 1;

	}

retry:
@@ -759,7 +757,7 @@ retry: 
				continue;

			}



			if (unlikely(is_range) && page->index > end) {

			if (!wbc->range_cyclic && page->index > end) {

				done = 1;

				unlock_page(page);

				continue;
@@ -810,7 +808,7 @@ retry: 
		index = 0;

		goto retry;

	}

	if (!is_range)

	if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))

		mapping->writeback_index = index;

	if (bio)

		mpage_bio_submit(WRITE, bio);

fs/sync.c

+1 −1
Original line number Diff line number Diff line
@@ -100,7 +100,7 @@ asmlinkage long sys_sync_file_range(int fd, loff_t offset, loff_t nbytes, 
	}



	if (nbytes == 0)

		endbyte = -1;

		endbyte = LLONG_MAX;

	else

		endbyte--;		/* inclusive */

include/linux/kernel.h

+3 −0
Original line number Diff line number Diff line
@@ -24,6 +24,9 @@ extern const char linux_banner[]; 
#define LONG_MAX	((long)(~0UL>>1))

#define LONG_MIN	(-LONG_MAX - 1)

#define ULONG_MAX	(~0UL)

#define LLONG_MAX	((long long)(~0ULL>>1))

#define LLONG_MIN	(-LLONG_MAX - 1)

#define ULLONG_MAX	(~0ULL)



#define STACK_MAGIC	0xdeadbeef