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Re: [PATCH v4 04/11] 9p: darwin: Handle struct dirent differences
From: |
Christian Schoenebeck |
Subject: |
Re: [PATCH v4 04/11] 9p: darwin: Handle struct dirent differences |
Date: |
Mon, 07 Feb 2022 15:41:12 +0100 |
On Sonntag, 6. Februar 2022 21:07:12 CET Will Cohen wrote:
> From: Keno Fischer <keno@juliacomputing.com>
>
> On darwin d_seekoff exists, but is optional and does not seem to
> be commonly used by file systems. Use `telldir` instead to obtain
> the seek offset and inject it into d_seekoff, and create a
> qemu_dirent_off helper to call it appropriately when appropriate.
>
> Signed-off-by: Keno Fischer <keno@juliacomputing.com>
> [Michael Roitzsch: - Rebase for NixOS]
> Signed-off-by: Michael Roitzsch <reactorcontrol@icloud.com>
> [Will Cohen: - Adjust to pass testing
> - Ensure that d_seekoff is filled using telldir
> on darwin, and create qemu_dirent_off helper
> to decide which to access]
> [Fabian Franz: - Add telldir error handling for darwin]
> [Will Cohen: - Ensure that telldir error handling uses
> signed int]
> Signed-off-by: Fabian Franz <fabianfranz.oss@gmail.com>
> Signed-off-by: Will Cohen <wwcohen@gmail.com>
> ---
> hw/9pfs/9p-local.c | 9 +++++++++
> hw/9pfs/9p-proxy.c | 16 +++++++++++++++-
> hw/9pfs/9p-synth.c | 4 ++++
> hw/9pfs/9p-util.h | 17 +++++++++++++++++
> hw/9pfs/9p.c | 15 +++++++++++++--
> hw/9pfs/codir.c | 7 +++++++
> 6 files changed, 65 insertions(+), 3 deletions(-)
>
> diff --git a/hw/9pfs/9p-local.c b/hw/9pfs/9p-local.c
> index 1a5e3eed73..7137a28109 100644
> --- a/hw/9pfs/9p-local.c
> +++ b/hw/9pfs/9p-local.c
> @@ -559,6 +559,15 @@ static struct dirent *local_readdir(FsContext *ctx,
> V9fsFidOpenState *fs)
>
> again:
> entry = readdir(fs->dir.stream);
> +#ifdef CONFIG_DARWIN
> + int td;
> + td = telldir(fs->dir.stream);
> + /* If telldir fails, fail the entire readdir call */
> + if (td < 0) {
> + return NULL;
> + }
> + entry->d_seekoff = td;
> +#endif
> if (!entry) {
> return NULL;
> }
'entry' may be NULL, so the 'if (!entry) {' check should be before the Darwin
specific code to avoid a crash on macOS.
> diff --git a/hw/9pfs/9p-proxy.c b/hw/9pfs/9p-proxy.c
> index b1664080d8..8b4b5cf7dc 100644
> --- a/hw/9pfs/9p-proxy.c
> +++ b/hw/9pfs/9p-proxy.c
> @@ -706,7 +706,21 @@ static off_t proxy_telldir(FsContext *ctx,
> V9fsFidOpenState *fs)
>
> static struct dirent *proxy_readdir(FsContext *ctx, V9fsFidOpenState *fs)
> {
> - return readdir(fs->dir.stream);
> + struct dirent *entry;
> + entry = readdir(fs->dir.stream);
> +#ifdef CONFIG_DARWIN
> + if (!entry) {
> + return NULL;
> + }
> + int td;
> + td = telldir(fs->dir.stream);
> + /* If telldir fails, fail the entire readdir call */
> + if (td < 0) {
> + return NULL;
> + }
> + entry->d_seekoff = td;
> +#endif
> + return entry;
> }
>
> static void proxy_seekdir(FsContext *ctx, V9fsFidOpenState *fs, off_t off)
> diff --git a/hw/9pfs/9p-synth.c b/hw/9pfs/9p-synth.c
> index 4a4a776d06..e264a03eef 100644
> --- a/hw/9pfs/9p-synth.c
> +++ b/hw/9pfs/9p-synth.c
> @@ -222,7 +222,11 @@ static void synth_direntry(V9fsSynthNode *node,
> {
> strcpy(entry->d_name, node->name);
> entry->d_ino = node->attr->inode;
> +#ifdef CONFIG_DARWIN
> + entry->d_seekoff = off + 1;
> +#else
> entry->d_off = off + 1;
> +#endif
> }
>
> static struct dirent *synth_get_dentry(V9fsSynthNode *dir,
> diff --git a/hw/9pfs/9p-util.h b/hw/9pfs/9p-util.h
> index 546f46dc7d..accbec9987 100644
> --- a/hw/9pfs/9p-util.h
> +++ b/hw/9pfs/9p-util.h
> @@ -79,3 +79,20 @@ ssize_t fremovexattrat_nofollow(int dirfd, const char
> *filename, const char *name);
>
> #endif
> +
> +
> +/**
> + * Darwin has d_seekoff, which appears to function similarly to d_off.
> + * However, it does not appear to be supported on all file systems,
> + * so ensure it is manually injected earlier and call here when
> + * needed.
> + */
> +
Nitpicking: no blank line here please.
> +inline off_t qemu_dirent_off(struct dirent *dent)
> +{
> +#ifdef CONFIG_DARWIN
> + return dent->d_seekoff;
> +#else
> + return dent->d_off;
> +#endif
> +}
> diff --git a/hw/9pfs/9p.c b/hw/9pfs/9p.c
> index 1563d7b7c6..cf694da354 100644
> --- a/hw/9pfs/9p.c
> +++ b/hw/9pfs/9p.c
> @@ -27,6 +27,7 @@
> #include "virtio-9p.h"
> #include "fsdev/qemu-fsdev.h"
> #include "9p-xattr.h"
> +#include "9p-util.h"
> #include "coth.h"
> #include "trace.h"
> #include "migration/blocker.h"
> @@ -2281,7 +2282,11 @@ static int coroutine_fn
> v9fs_do_readdir_with_stat(V9fsPDU *pdu, count += len;
> v9fs_stat_free(&v9stat);
> v9fs_path_free(&path);
> - saved_dir_pos = dent->d_off;
> + saved_dir_pos = qemu_dirent_off(dent);
> + if (saved_dir_pos < 0) {
> + err = saved_dir_pos;
> + break;
> + }
> }
That check is no longer needed here, is it?
>
> v9fs_readdir_unlock(&fidp->fs.dir);
> @@ -2420,6 +2425,7 @@ static int coroutine_fn v9fs_do_readdir(V9fsPDU *pdu,
> V9fsFidState *fidp, V9fsString name;
> int len, err = 0;
> int32_t count = 0;
> + off_t off;
> struct dirent *dent;
> struct stat *st;
> struct V9fsDirEnt *entries = NULL;
> @@ -2480,12 +2486,17 @@ static int coroutine_fn v9fs_do_readdir(V9fsPDU
> *pdu, V9fsFidState *fidp, qid.version = 0;
> }
>
> + off = qemu_dirent_off(dent);
> + if (off < 0) {
> + err = off;
> + break;
> + }
Likewise: is this check still needed?
> v9fs_string_init(&name);
> v9fs_string_sprintf(&name, "%s", dent->d_name);
>
> /* 11 = 7 + 4 (7 = start offset, 4 = space for storing count) */
> len = pdu_marshal(pdu, 11 + count, "Qqbs",
> - &qid, dent->d_off,
> + &qid, off,
> dent->d_type, &name);
>
> v9fs_string_free(&name);
> diff --git a/hw/9pfs/codir.c b/hw/9pfs/codir.c
> index 032cce04c4..fac6759a64 100644
> --- a/hw/9pfs/codir.c
> +++ b/hw/9pfs/codir.c
> @@ -167,7 +167,14 @@ static int do_readdir_many(V9fsPDU *pdu, V9fsFidState
> *fidp, }
>
> size += len;
> + /* This conditional statement is identical in
> + * function to qemu_dirent_off, described in 9p-util.h,
> + * since that header cannot be included here. */
> +#ifdef CONFIG_DARWIN
> + saved_dir_pos = dent->d_seekoff;
> +#else
> saved_dir_pos = dent->d_off;
> +#endif
Why can't the header not be included here? Obvious preference would be to use
qemu_dirent_off() here as well, to have control at one central code location.
> }
>
> /* restore (last) saved position */
- [PATCH v4 02/11] 9p: Rename 9p-util -> 9p-util-linux, (continued)
- [PATCH v4 08/11] 9p: darwin: Compatibility for f/l*xattr, Will Cohen, 2022/02/06
- [PATCH v4 06/11] 9p: darwin: Move XATTR_SIZE_MAX->P9_XATTR_SIZE_MAX, Will Cohen, 2022/02/06
- [PATCH v4 09/11] 9p: darwin: Implement compatibility for mknodat, Will Cohen, 2022/02/06
- Re: [PATCH v4 09/11] 9p: darwin: Implement compatibility for mknodat, Philippe Mathieu-Daudé, 2022/02/06
- Re: [PATCH v4 09/11] 9p: darwin: Implement compatibility for mknodat, Will Cohen, 2022/02/06
- Re: [PATCH v4 09/11] 9p: darwin: Implement compatibility for mknodat, Greg Kurz, 2022/02/07
- Re: [PATCH v4 09/11] 9p: darwin: Implement compatibility for mknodat, Philippe Mathieu-Daudé, 2022/02/07
- Re: [PATCH v4 09/11] 9p: darwin: Implement compatibility for mknodat, Greg Kurz, 2022/02/07
- Re: [PATCH v4 09/11] 9p: darwin: Implement compatibility for mknodat, Dr. David Alan Gilbert, 2022/02/07