From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
To: Michael Tokarev <mjt@tls.msk.ru>
Cc: qemu-trivial@nongnu.org, qemu-devel@nongnu.org
Subject: Re: [Qemu-devel] [PATCH] 9pfs-local: simplify/optimize local_mapped_attr_path()
Date: Tue, 10 Mar 2015 23:00:09 +0530 [thread overview]
Message-ID: <87k2yorc9q.fsf@linux.vnet.ibm.com> (raw)
In-Reply-To: <1425503036-23707-1-git-send-email-mjt@msgid.tls.msk.ru>
Michael Tokarev <mjt@tls.msk.ru> writes:
> Omit one unnecessary memory allocation for components of the path
> and create the resulting path directly given lengths of the components.
>
> This uses (char*) cast because basename() accepts a char* without const,
> for unknown reason. Maybe it is better to use strrchr(), but I'm not
> sure for various forms of directory component delimiter.
basename(3) says:
Both dirname() and basename() may modify the contents of path, so it may
be desirable to pass a copy when calling one of these functions
>
> And according to basename(3) manpage, it might return different strings
> for various corner cases, for example for empty argument it returns a
> string "." which is obviously at some other address, so both the old
> code and new code will do a bad thing here. So maybe it is actually
> better to use strrchr() after all.
>
> Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
> ---
> hw/9pfs/virtio-9p-local.c | 17 ++++-------------
> 1 file changed, 4 insertions(+), 13 deletions(-)
>
> diff --git a/hw/9pfs/virtio-9p-local.c b/hw/9pfs/virtio-9p-local.c
> index d05c917..fddc242 100644
> --- a/hw/9pfs/virtio-9p-local.c
> +++ b/hw/9pfs/virtio-9p-local.c
> @@ -45,19 +45,10 @@
>
> static char *local_mapped_attr_path(FsContext *ctx, const char *path)
> {
> - char *dir_name;
> - char *tmp_path = g_strdup(path);
> - char *base_name = basename(tmp_path);
> - char *buffer;
> -
> - /* NULL terminate the directory */
> - dir_name = tmp_path;
> - *(base_name - 1) = '\0';
> -
> - buffer = g_strdup_printf("%s/%s/%s/%s",
> - ctx->fs_root, dir_name, VIRTFS_META_DIR, base_name);
> - g_free(tmp_path);
> - return buffer;
> + const char *name = basename((char*)path);
as per the man page basename could end up modifying 'path' and we don't
want to modify the input argument of the function.
> + int dirlen = name - path - 1;
> + return g_strdup_printf("%s/%.*s/%s/%s", ctx->fs_root,
> + dirlen, path, VIRTFS_META_DIR, name);
> }
>
> static FILE *local_fopen(const char *path, const char *mode)
I am not sure whether we really need all these cleanups without really
fixing anyi specific issue.
-aneesh
next prev parent reply other threads:[~2015-03-10 17:30 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-04 21:03 [Qemu-devel] [PATCH] 9pfs-local: simplify/optimize local_mapped_attr_path() Michael Tokarev
2015-03-05 1:13 ` Fam Zheng
2015-03-10 6:15 ` Michael Tokarev
2015-03-10 17:30 ` Aneesh Kumar K.V [this message]
2015-03-12 6:50 ` Michael Tokarev
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=87k2yorc9q.fsf@linux.vnet.ibm.com \
--to=aneesh.kumar@linux.vnet.ibm.com \
--cc=mjt@tls.msk.ru \
--cc=qemu-devel@nongnu.org \
--cc=qemu-trivial@nongnu.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).