Jonathan Nieder wrote:
> To fix that, we should fsync() each file with multiple hard links only
> once and then rename all links, so the logic to skip fsync would be no
> longer needed.
... and here's a patch on top implementing that.
---
debian/changelog | 13 ++++++-------
src/archives.c | 38 ++++++++------------------------------
2 files changed, 14 insertions(+), 37 deletions(-)
diff --git a/debian/changelog b/debian/changelog
index e5de69d4..24d5df9f 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -189,13 +189,12 @@ dpkg (1.16.1~jrn) local; urgency=low
[ Jonathan Nieder ]
* Defer installing hard links with their final name until the file has
been fsynced.
- * Open extracted files for reading, not writing, in order to fsync them.
- Otherwise the open can error out when preparing to rename a binary into
- place that has a hard link already in use. Regression introduced in
- 1.15.6.1. Closes: #635683
- * If fsync fails with EBADF, as it is documented to on older platforms
- when fd is not opened for writing, reopen the file for writing and try
- again. If that fails with ETXTBSY, just skip the fsync.
+ * Suppress the deferred fsync before renaming hard links to files that
+ have already been fsynced and linked before. This prevents errors from
+ opening binaries for writing when another link is already in use.
+ Regression introduced in 1.15.6.1. Closes: #635683
+ * When possible, open extracted files for reading, not writing, in order
+ to fsync them.
[ Updated dpkg translations ]
* German (Sven Joachim). Closes: #620312
diff --git a/src/archives.c b/src/archives.c
index c221f388..61eee5be 100644
--- a/src/archives.c
+++ b/src/archives.c
@@ -851,6 +851,13 @@ tarobject(void *ctx, struct tar_entry *ti)
* in .dpkg-new.
*/
+ /*
+ * Files with multiple links only need one fsync: before the first link
+ * is renamed into place.
+ */
+ if (ti->type == tar_filetype_hardlink)
+ nifd->namenode->flags &= ~fnnf_deferred_fsync;
+
if (ti->type == tar_filetype_file || ti->type == tar_filetype_symlink ||
ti->type == tar_filetype_hardlink) {
nifd->namenode->flags |= fnnf_deferred_rename;
@@ -920,32 +927,6 @@ deferred_extract_fsync(const char *path)
* The documentation for some Unixen (e.g., AIX) says fsync
* requires a file descriptor open for writing and will
* return EBADF otherwise.
- *
- * Unfortunately, opening a file for writing fails if that
- * file happens to be a binary whose text is mapped. That
- * can happen in two cases:
- *
- * A) We are installing a hard link to a binary that was
- * already installed into place and run. In that case,
- * we've already done the fsync, so it's safe to skip.
- *
- * B) Some obnoxious user decided to run the .dpkg-new
- * file directly.
- *
- * For now let's assume we are in case A and skip the fsync
- * when errno == ETXTBSY. XXX: It would be better to prevent (A)
- * higher in the call stack and fall back to sync() here.
- *
- * On Linux, we just open the file for reading, fsync does not
- * return EBADF, and the behavior is as simple as
- *
- * fd = open(...);
- * if (fd < 0)
- * ohshite(...);
- * if (fsync(...))
- * ohshite(...);
- * if (close(...))
- * ohshite(...);
*/
int fd;
@@ -961,11 +942,8 @@ deferred_extract_fsync(const char *path)
/* Try again with an fd open for writing. */
close(fd);
fd = open(path, O_WRONLY);
- if (fd < 0) {
- if (errno == ETXTBSY)
- goto done;
+ if (fd < 0)
ohshite(_("unable to open '%.255s'"), path);
- }
if (fsync(fd))
ohshite(_("unable to sync file '%.255s'"), path);
--
1.7.6
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