Re: [PATCH v4 2/2] merge-ort: return early when failing to write a blob
From: Elijah Newren <hidden>
Date: 2022-09-27 08:12:11
On Mon, Sep 26, 2022 at 2:55 PM Johannes Schindelin via GitGitGadget [off-list ref] wrote:
From: Johannes Schindelin <redacted> In the previous commit, we fixed a segmentation fault when a tree object could not be written. However, before the tree object is written, `merge-ort` wants to write out a blob object (except in cases where the merge results in a blob that already exists in the database). And this can fail, too, but we ignore that write failure so far. Since we will always write out a new tree object in addition to the blob (and if the blob did not exist in the database yet, we can be certain that the tree object did not exist yet), the merge will _still_ fail at that point, but it does unnecessary work by continuing after the blob could not be written.
I don't think this is quite true. I've had a number of users come to me with "messed up git repositories" where I eventually discover that users just randomly add "sudo" to some of their commands because when things don't work, sometimes "sudo" fixes it. That means they've created stuff in their .git directory which may be owned by root, perhaps even some of the .git/objects/XX directories. However, they may have other .git/objects/XX directories owned by their normal user. If just some .git/objects/XX directories are owned by root and not others, then it may be when users run git commands as themselves that some things can be written to the object database but not others. In particular, it could be that writing blob objects fail, but writing a tree object which references those blobs succeeds.
quoted hunk ↗ jump to hunk
Let's pay close attention and error out early if the blob could not be written. This reduces the error output of t4301.25 ("merge-ort fails gracefully in a read-only repository") from: error: insufficient permission for adding an object to repository database ./objects error: error: Unable to add numbers to database error: insufficient permission for adding an object to repository database ./objects error: error: Unable to add greeting to database error: insufficient permission for adding an object to repository database ./objects fatal: failure to merge to: error: insufficient permission for adding an object to repository database ./objects error: error: Unable to add numbers to database fatal: failure to merge Note: This patch adjusts two variable declarations from `unsigned` to `int` because their purpose is to hold the return value of `handle_content_merge()`, which is of type `int`. The existing users of those variables are only interested whether that variable is zero or non-zero, therefore this type change does not affect the existing code. Signed-off-by: Johannes Schindelin <redacted> --- merge-ort.c | 28 +++++++++++++++++++--------- 1 file changed, 19 insertions(+), 9 deletions(-)diff --git a/merge-ort.c b/merge-ort.c index f3bdce1041a..e5f41cce481 100644 --- a/merge-ort.c +++ b/merge-ort.c@@ -2807,6 +2807,8 @@ static int process_renames(struct merge_options *opt, pathnames, 1 + 2 * opt->priv->call_depth, &merged); + if (clean_merge < 0) + return -1; if (!clean_merge && merged.mode == side1->stages[1].mode && oideq(&merged.oid, &side1->stages[1].oid))@@ -2916,7 +2918,7 @@ static int process_renames(struct merge_options *opt, struct version_info merged; struct conflict_info *base, *side1, *side2; - unsigned clean; + int clean; pathnames[0] = oldpath; pathnames[other_source_index] = oldpath;@@ -2937,6 +2939,8 @@ static int process_renames(struct merge_options *opt, pathnames, 1 + 2 * opt->priv->call_depth, &merged); + if (clean < 0) + return -1; memcpy(&newinfo->stages[target_index], &merged, sizeof(merged));@@ -3806,10 +3810,10 @@ static int write_completed_directory(struct merge_options *opt, } /* Per entry merge function */ -static void process_entry(struct merge_options *opt, - const char *path, - struct conflict_info *ci, - struct directory_versions *dir_metadata) +static int process_entry(struct merge_options *opt, + const char *path, + struct conflict_info *ci, + struct directory_versions *dir_metadata) { int df_file_index = 0;@@ -3823,7 +3827,7 @@ static void process_entry(struct merge_options *opt, record_entry_for_tree(dir_metadata, path, &ci->merged); if (ci->filemask == 0) /* nothing else to handle */ - return; + return 0; assert(ci->df_conflict); }@@ -3870,7 +3874,7 @@ static void process_entry(struct merge_options *opt, */ if (ci->filemask == 1) { ci->filemask = 0; - return; + return 0; } /*@@ -4065,7 +4069,7 @@ static void process_entry(struct merge_options *opt, } else if (ci->filemask >= 6) { /* Need a two-way or three-way content merge */ struct version_info merged_file; - unsigned clean_merge; + int clean_merge; struct version_info *o = &ci->stages[0]; struct version_info *a = &ci->stages[1]; struct version_info *b = &ci->stages[2];@@ -4074,6 +4078,8 @@ static void process_entry(struct merge_options *opt, ci->pathnames, opt->priv->call_depth * 2, &merged_file); + if (clean_merge < 0) + return -1; ci->merged.clean = clean_merge && !ci->df_conflict && !ci->path_conflict; ci->merged.result.mode = merged_file.mode;@@ -4169,6 +4175,7 @@ static void process_entry(struct merge_options *opt, /* Record metadata for ci->merged in dir_metadata */ record_entry_for_tree(dir_metadata, path, &ci->merged); + return 0; } static void prefetch_for_content_merges(struct merge_options *opt,@@ -4285,7 +4292,10 @@ static int process_entries(struct merge_options *opt, record_entry_for_tree(&dir_metadata, path, mi); else { struct conflict_info *ci = (struct conflict_info *)mi; - process_entry(opt, path, ci, &dir_metadata); + if (process_entry(opt, path, ci, &dir_metadata) < 0) { + ret = -1; + goto cleanup; + }; } } trace2_region_leave("merge", "processing", opt->repo); --gitgitgadget
Patch looks good to me, though.