[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: OGAWA 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: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
OGAWA Hirofumi 2006-06-23 02:03:26 -07:00 committed by Linus Torvalds
parent 4c91c3648c
commit 111ebb6e6f
9 changed files with 40 additions and 31 deletions

View file

@ -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 @@ static int cifs_writepages(struct address_space *mapping,
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 @@ static int cifs_writepages(struct address_space *mapping,
index = 0;
goto retry;
}
if (!is_range)
if (wbc->range_cyclic || (range_whole && wbc->nr_to_write > 0))
mapping->writeback_index = index;
FreeXid(xid);

View file

@ -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))

View file

@ -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 @@ mpage_writepages(struct address_space *mapping,
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 @@ mpage_writepages(struct address_space *mapping,
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);

View file

@ -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 */

View file

@ -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

View file

@ -50,14 +50,15 @@ struct writeback_control {
* a hint that the filesystem need only write out the pages inside that
* byterange. The byte at `end' is included in the writeout request.
*/
loff_t start;
loff_t end;
loff_t range_start;
loff_t range_end;
unsigned nonblocking:1; /* Don't get stuck on request queues */
unsigned encountered_congestion:1; /* An output: a queue is full */
unsigned for_kupdate:1; /* A kupdate writeback */
unsigned for_reclaim:1; /* Invoked from the page allocator */
unsigned for_writepages:1; /* This is a writepages() call */
unsigned range_cyclic:1; /* range_start is cyclic */
};
/*

View file

@ -190,8 +190,8 @@ int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
struct writeback_control wbc = {
.sync_mode = sync_mode,
.nr_to_write = mapping->nrpages * 2,
.start = start,
.end = end,
.range_start = start,
.range_end = end,
};
if (!mapping_cap_writeback_dirty(mapping))
@ -204,7 +204,7 @@ int __filemap_fdatawrite_range(struct address_space *mapping, loff_t start,
static inline int __filemap_fdatawrite(struct address_space *mapping,
int sync_mode)
{
return __filemap_fdatawrite_range(mapping, 0, 0, sync_mode);
return __filemap_fdatawrite_range(mapping, 0, LLONG_MAX, sync_mode);
}
int filemap_fdatawrite(struct address_space *mapping)

View file

@ -204,6 +204,7 @@ static void balance_dirty_pages(struct address_space *mapping)
.sync_mode = WB_SYNC_NONE,
.older_than_this = NULL,
.nr_to_write = write_chunk,
.range_cyclic = 1,
};
get_dirty_limits(&wbs, &background_thresh,
@ -331,6 +332,7 @@ static void background_writeout(unsigned long _min_pages)
.older_than_this = NULL,
.nr_to_write = 0,
.nonblocking = 1,
.range_cyclic = 1,
};
for ( ; ; ) {
@ -407,6 +409,7 @@ static void wb_kupdate(unsigned long arg)
.nr_to_write = 0,
.nonblocking = 1,
.for_kupdate = 1,
.range_cyclic = 1,
};
sync_supers();

View file

@ -339,6 +339,8 @@ pageout_t pageout(struct page *page, struct address_space *mapping)
struct writeback_control wbc = {
.sync_mode = WB_SYNC_NONE,
.nr_to_write = SWAP_CLUSTER_MAX,
.range_start = 0,
.range_end = LLONG_MAX,
.nonblocking = 1,
.for_reclaim = 1,
};