GNU C Library master sources branch master updated. glibc-2.22-305-g032f225

[carlos at sourceware dot org]

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http://sourceware.org/git/gitweb.cgi?p=glibc.git;a=commitdiff;h=032f2250086fec2ebda3832f260c3a8955cf281f

commit 032f2250086fec2ebda3832f260c3a8955cf281f
Author: Carlos O'Donell <carlos@systemhalted.org>
Date:   Tue Sep 29 11:32:36 2015 -0400

    Files open O_WRONLY not supported in fallocate emulation.
    
    In the posix_fallocate description in the manual we list various
    drawbacks with the emulation, including the fact that a file opened
    with O_APPEND fails with EBADF. Similarly a file opened with O_WRONLY
    fails with EBADF. We must be able to emulate a compare-and-swap via
    pread/compare/pwrite in order to make the emulation as safe as possible.
    It is not acceptable to ignore the read failure because it could result
    in significant data loss across all of the blocks. There is no other way
    to make this work without a true atomic CAS and SIGBUS handler (which
    is looking more attractive as a way to remove the race condition).
    
    This patch adds O_WRONLY to the manual as another bullet to clarify the
    limits of the emulation.
    
    Manual looks good in PDF.

diff --git a/ChangeLog b/ChangeLog
index 8b5050b..8851c6b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+2015-09-29  Carlos O'Donell  <carlos@redhat.com>
+
+	* manual/filesys.texi (Storage Allocation): Document that
+	posix_fallocate emulation fails when fd is open with O_WRONLY.
+
 2015-09-28  Joseph Myers  <joseph@codesourcery.com>
 
 	[BZ #19016]
diff --git a/manual/filesys.texi b/manual/filesys.texi
index ed4f5fd..4064885 100644
--- a/manual/filesys.texi
+++ b/manual/filesys.texi
@@ -3300,6 +3300,10 @@ underlying file in the to-be-allocated area.  Non-null bytes could be
 overwritten with null bytes.
 
 @item
+If @var{fd} has been opened with the @code{O_WRONLY} flag, the function
+will fail with an @code{errno} value of @code{EBADF}.
+
+@item
 If @var{fd} has been opened with the @code{O_APPEND} flag, the function
 will fail with an @code{errno} value of @code{EBADF}.
 

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog           |    5 +++++
 manual/filesys.texi |    4 ++++
 2 files changed, 9 insertions(+), 0 deletions(-)


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