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Re: Nasty double-replace copy-on-update bug

From: David Glasser <glasser_at_davidglasser.net>
Date: 2007-10-18 23:44:27 CEST

On 10/18/07, Ben Collins-Sussman <sussman@red-bean.com> wrote:
> Let me elaborate on this bug: it's something epg, glasser and I
> discovered fooling around within Google today. It only exists using
> the latest 1.5 server and client.
>
> The basic symptom is: you start a checkout, and at some point the 1.5
> server says "add_file(foo, copyfrom=bar@10". The client searches
> around for bar@10 in the working copy, and finds it. Or rather it
> *thinks* it finds it, but it's actually the wrong version of the file.
> So, rather than just doing a side svn_ra_get_file() fetch (as it
> should), it installs the wrong version of the file with a quick wc-wc
> copy. The server then tries to apply a txdelta to the file, and the
> checksum fails... boom, failed checkout.
>
> The question is: why the wc-searching routine
> (update_editor.c:locate_copyfrom()) think that it's found the correct
> version of the file, when it's not? Answer: it seems to be getting
> stale svn_wc_entry_t information. It's reading a couple of entries
> files from disk, rather than from a more recent adm_access set still
> held in memory, and getting an incorrect (stale) last-changed-rev
> value. From poking around in gdb, it seems that the entry_t's which
> are write-cached in memory are correct -- they have the proper
> last-changed-rev values, but simply aren't flushed to disk yet.
>
> I attempted to solve this by passing in the edit_baton->access_set to
> the searching routine, but it's not fixing the problem. I've attached
> my patch-in-progress below. Can we get some more eyes on this
> problem?

Define "not fixing the problem". It makes my script pass for me...

--dave

>
>
>
> Index: subversion/libsvn_wc/update_editor.c
> ===================================================================
> --- subversion/libsvn_wc/update_editor.c (revision 27277)
> +++ subversion/libsvn_wc/update_editor.c (working copy)
> @@ -2829,6 +2829,8 @@
> copy for an pre-existing versioned file which is exactly equal to
> COPYFROM_PATH@COPYFROM_REV.
>
> + Use existing ASSOCIATED access-sets to examine svn_wc_entry_t's.
> +
> If the file is found, return the absolute path to it in
> *RETURN_PATH, as well as a (read-only) access_t for its parent in
> *RETURN_ACCESS. If the file isn't found, set *RETURN_PATH to NULL.
> @@ -2838,6 +2840,7 @@
> svn_revnum_t copyfrom_rev,
> const char *dest_dir,
> const svn_wc_entry_t *dest_entry,
> + svn_wc_adm_access_t *associated,
> const char **return_path,
> svn_wc_adm_access_t **return_access,
> apr_pool_t *pool)
> @@ -2897,10 +2900,10 @@
> SVN_ERR(svn_io_check_path(cwd->data, &kind, subpool));
> if (kind != svn_node_dir)
> return SVN_NO_ERROR;
> - err = svn_wc_adm_open3(&ancestor_access, NULL, cwd->data,
> - FALSE, /* open read-only, please */
> - 0, /* open only this directory */
> - NULL, NULL, subpool);
> + err = svn_wc_adm_probe_try3(&ancestor_access, associated, cwd->data,
> + FALSE, /* open read-only, please */
> + 0, /* open only this directory */
> + NULL, NULL, subpool);
> if (err && err->apr_err == SVN_ERR_WC_NOT_DIRECTORY)
> {
> /* The common ancestor directory isn't version-controlled. */
> @@ -2941,10 +2944,10 @@
> return SVN_NO_ERROR;
>
> /* Next: is the file's parent-dir under version control? */
> - err = svn_wc_adm_open3(&ancestor_access, NULL, cwd_parent->data,
> - FALSE, /* open read-only, please */
> - 0, /* open only the parent dir */
> - NULL, NULL, pool);
> + err = svn_wc_adm_probe_try3(&ancestor_access, associated, cwd_parent->data,
> + FALSE, /* open read-only, please */
> + 0, /* open only the parent dir */
> + NULL, NULL, pool);
> if (err && err->apr_err == SVN_ERR_WC_NOT_DIRECTORY)
> {
> svn_error_clear(err);
> @@ -3052,7 +3055,7 @@
> /* Attempt to locate the copyfrom_path in the working copy first. */
> SVN_ERR(svn_wc_entry(&path_entry, pb->path, eb->adm_access, FALSE, pool));
> err = locate_copyfrom(copyfrom_path, copyfrom_rev,
> - pb->path, path_entry,
> + pb->path, path_entry, eb->adm_access,
> &src_path, &src_access, pool);
> if (err && err->apr_err == SVN_ERR_WC_COPYFROM_PATH_NOT_FOUND)
> svn_error_clear(err);
>

-- 
David Glasser | glasser_at_davidglasser.net | http://www.davidglasser.net/
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Received on Thu Oct 18 23:44:38 2007

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