[PATCH 1/3] stat_validity: handle non-regular files
- From
Jeff King <peff@peff.net>
- Date
- May 22, 2015, 23:51 UTC
- Message-ID
- <20150522235143.GA4818@peff.net>
- In-Reply-To
- <20150522235116.GA4300@peff.net>
The stat_validity code was originally written to avoid re-reading the packed-refs file when it has not changed. It makes sure that the file continues to match S_ISREG() when we check it.
However, we can use the same concept on a directory to see whether it has been modified. Even though we still have to touch the filesystem to do the stat, this can provide a speedup even over opendir/readdir/closedir, especially on high-latency filesystems like NFS.
This patch adds a "mode" field to stat_validity, which lets us check that the mode has stayed the same (rather than explicitly checking that it is a regular file).
As a bonus cleanup, we can stop allocating the embedded "stat_data" on the heap. Prior to this patch, we needed to represent the case where the file did not exist, and we used "sv->sd == NULL" for that. Now we can simply check that "sv->mode" is 0.
Signed-off-by: Jeff King <peff@peff.net> --- cache.h | 3 ++- read-cache.c | 16 ++++++---------- 2 files changed, 8 insertions(+), 11 deletions(-)
diff --git a/cache.h b/cache.h index c97d807..2941e7e 100644 --- a/cache.h +++ b/cache.h @@ -1660,7 +1660,8 @@ int sane_execvp(const char *file, char *const argv[]); * for the index. */ struct stat_validity { - struct stat_data *sd; + struct stat_data sd; + unsigned mode; }; void stat_validity_clear(struct stat_validity *sv); diff --git a/read-cache.c b/read-cache.c index 36ff89f..115b000 100644 --- a/read-cache.c +++ b/read-cache.c @@ -2279,8 +2279,7 @@ void *read_blob_data_from_index(struct index_state *istate, const char *path, un void stat_validity_clear(struct stat_validity *sv) { - free(sv->sd); - sv->sd = NULL; + memset(sv, 0, sizeof(*sv)); } int stat_validity_check(struct stat_validity *sv, const char *path) @@ -2288,21 +2287,18 @@ int stat_validity_check(struct stat_validity *sv, const char *path) struct stat st; if (stat(path, &st) < 0) - return sv->sd == NULL; - if (!sv->sd) - return 0; - return S_ISREG(st.st_mode) && !match_stat_data(sv->sd, &st); + return sv->mode == 0; + return sv->mode == st.st_mode && !match_stat_data(&sv->sd, &st); } void stat_validity_update(struct stat_validity *sv, int fd) { struct stat st; - if (fstat(fd, &st) < 0 || !S_ISREG(st.st_mode)) + if (fstat(fd, &st) < 0) stat_validity_clear(sv); else { - if (!sv->sd) - sv->sd = xcalloc(1, sizeof(struct stat_data)); - fill_stat_data(sv->sd, &st); + sv->mode = st.st_mode; + fill_stat_data(&sv->sd, &st); } }
-- 2.4.1.538.g69ac333