From 111ebb6e6f7bd7de6d722c5848e95621f43700d9 Mon Sep 17 00:00:00 2001 From: OGAWA Hirofumi Date: Fri, 23 Jun 2006 02:03:26 -0700 Subject: [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 Cc: Nathan Scott Cc: Anton Altaparmakov Cc: Steven French Cc: "Vladimir V. Saveliev" Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/cifs/file.c | 24 +++++++++++------------- 1 file changed, 11 insertions(+), 13 deletions(-) (limited to 'fs/cifs') diff --git a/fs/cifs/file.c b/fs/cifs/file.c index e2b4ce1..487ea8b 100644 --- a/fs/cifs/file.c +++ b/fs/cifs/file.c @@ -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); -- cgit v1.1