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[PATCH 13/17] Ensure core.packedGitWindowSize cannot be less than 2 pages.

From
Shawn O. Pearce <spearce@spearce.org>
Date
Dec 23, 2006, 07:34 UTC
Message-ID
<20061223073438.GN9837@spearce.org>
In-Reply-To
<53b67707929c7f051f6d384c5d96e653bfa8419c.1166857884.git.spearce@spearce.org>

We cannot allow a window to be smaller than 2 system pages. This limitation is necessary to support the feature of use_pack() where we always supply at least 20 bytes after the offset to help the object header and delta base parsing routines.

If packedGitWindowSize were allowed to be as small as 1 system page then we would be completely unable to access an object header which spanned over a page as we would never be able to arrange a mapping such that the header was contiguous in virtual memory.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
---
 config.c |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/config.c b/config.c
index a8ea063..edc42f4 100644
--- a/config.c
+++ b/config.c
@@ -302,8 +302,8 @@ int git_default_config(const char *var, const char *value)
 		int pgsz = getpagesize();
 		packed_git_window_size = git_config_int(var, value);
 		packed_git_window_size /= pgsz;
-		if (!packed_git_window_size)
-			packed_git_window_size = 1;
+		if (packed_git_window_size < 2)
+			packed_git_window_size = 2;
 		packed_git_window_size *= pgsz;
 		return 0;
 	}
-- 
1.4.4.3.g87d8
Previous: Shawn O. PearceNext: Shawn O. Pearce
Message 21 of 25 in “Replace unpack_entry_gently with unpack_entry.”
  1. 1/17 Replace unpack_entry_gently with unpack_entry.Shawn O. Pearce, Dec 23, 2006
  2. 2/17 Introduce new config option for mmap limit.Shawn O. Pearce, Dec 23, 2006
  3. 3/17 Refactor packed_git to prepare for sliding mmap windows.Shawn O. Pearce, Dec 23, 2006
  4. 4/17 Use off_t for index and pack file lengths.Shawn O. Pearce, Dec 23, 2006
  5. 5/17 Create read_or_die utility routine.Shawn O. Pearce, Dec 23, 2006
  6. 6/17 Refactor how we open pack files to prepare for multiple windows.Shawn O. Pearce, Dec 23, 2006
  7. 7/17 Replace use_packed_git with window cursors.Shawn O. Pearce, Dec 23, 2006
  8. 8/17 Loop over pack_windows when inflating/accessing data.Shawn O. Pearce, Dec 23, 2006
  9. 9/17 Document why header parsing won't exceed a window.Shawn O. Pearce, Dec 23, 2006
  10. 10/17 Unmap individual windows rather than entire files.Shawn O. Pearce, Dec 23, 2006
  11. 11/17 Fully activate the sliding window pack access.Shawn O. Pearce, Dec 23, 2006
  12. Linus TorvaldsDec 23, 2006
  13. Eric BlakeDec 23, 2006
  14. Johannes SchindelinDec 24, 2006
  15. Junio C HamanoDec 23, 2006
  16. Linus TorvaldsDec 23, 2006
  17. Johannes SchindelinDec 24, 2006
  18. Shawn PearceDec 24, 2006
  19. Shawn PearceDec 24, 2006
  20. 12/17 Load core configuration in git-verify-pack.Shawn O. Pearce, Dec 23, 2006
  21. 13/17 Ensure core.packedGitWindowSize cannot be less than 2 pages.Shawn O. Pearce, Dec 23, 2006
  22. 14/17 Improve error message when packfile mmap fails.Shawn O. Pearce, Dec 23, 2006
  23. 15/17 Support unmapping windows on 'temporary' packfiles.Shawn O. Pearce, Dec 23, 2006
  24. 16/17 Create pack_report() as a debugging aid.Shawn O. Pearce, Dec 23, 2006
  25. 17/17 Test suite for sliding window mmap implementation.Shawn O. Pearce, Dec 23, 2006

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