Re: [PATCH 09/11] mount.cc: Implement poor-man's cache
On Feb 3 12:38, Ben wrote: > > > On 18-01-2021 12:51, Corinna Vinschen via Cygwin-patches wrote: > > Ok, so hash_prefix reduces the path to a drive letter or the UNC path > > prefix and hashes it. However, what about partitions mounted to a > > subdir of, say, drive C? In that case the hashing goes awry, because > > you're comparing with the hash of drive C while the path is actually > > pointing to another partition. > > > How can I mount a partition as a subdir of drive C? > For some reason I can't: > $ mount /cygdrive/e/Temp/dummy /cygdrive/c/Temp/dummy/dummyone > mount: /cygdrive/c/Temp/dummy/dummyone: Invalid argument I wasn't talking about Cygwin mount points, but rather about Windows mount points. Since Windows 2000 a partition can be mounted into a directory of another partition. Only drive C: (ignoring non-harddisks) has to be mounted with a drive letter, all others can be mounted just as on Unix. But, yeah, Cygwin also supports bind mounts. Here's an example from my /etc/fstab.d user mount file: //remote/cygwin-src /cygwin nfs binary 0 0 /cygwin/pub /home/pub nfs bind 0 0 Corinna
Re: [PATCH 09/11] mount.cc: Implement poor-man's cache
On 18-01-2021 12:51, Corinna Vinschen via Cygwin-patches wrote: > Ok, so hash_prefix reduces the path to a drive letter or the UNC path > prefix and hashes it. However, what about partitions mounted to a > subdir of, say, drive C? In that case the hashing goes awry, because > you're comparing with the hash of drive C while the path is actually > pointing to another partition. > How can I mount a partition as a subdir of drive C? For some reason I can't: $ mount /cygdrive/e/Temp/dummy /cygdrive/c/Temp/dummy/dummyone mount: /cygdrive/c/Temp/dummy/dummyone: Invalid argument
Re: [PATCH 09/11] mount.cc: Implement poor-man's cache
On Jan 15 14:45, Ben Wijen wrote:
> Try to avoid NtQueryVolumeInformationFile.
> ---
> winsup/cygwin/mount.cc | 78 --
> winsup/cygwin/mount.h | 2 +-
> winsup/cygwin/path.cc | 2 +-
> winsup/cygwin/path.h | 1 +
> 4 files changed, 56 insertions(+), 27 deletions(-)
>
> diff --git a/winsup/cygwin/mount.cc b/winsup/cygwin/mount.cc
> index e0349815d..1d2b3a61a 100644
> --- a/winsup/cygwin/mount.cc
> +++ b/winsup/cygwin/mount.cc
> @@ -82,6 +82,32 @@ win32_device_name (const char *src_path, char *win32_path,
> device& dev)
>return true;
> }
>
> +static uint32_t
> +hash_prefix (const PUNICODE_STRING upath)
> +{
> + UNICODE_STRING prefix;
> + WCHAR *p;
> +
> + if (upath->Buffer[5] == L':' && upath->Buffer[6] == L'\\')
> +p = upath->Buffer + 6;
> + else
> +{
> + /* We're expecting an UNC path. Move p to the backslash after
> + "\??\UNC\server\share" or the trailing NUL. */
> + p = upath->Buffer + 7; /* Skip "\??\UNC" */
> + int bs_cnt = 0;
> +
> + while (*++p)
> +if (*p == L'\\')
> + if (++bs_cnt > 1)
> +break;
> +}
> + RtlInitCountedUnicodeString (&prefix, upath->Buffer,
> + (p - upath->Buffer) * sizeof(WCHAR));
> +
> + return hash_path_name ((ino_t) 0, &prefix);
> +}
> +
Ok, so hash_prefix reduces the path to a drive letter or the UNC path
prefix and hashes it. However, what about partitions mounted to a
subdir of, say, drive C? In that case the hashing goes awry, because
you're comparing with the hash of drive C while the path is actually
pointing to another partition.
> @@ -233,27 +281,7 @@ fs_info::update (PUNICODE_STRING upath, HANDLE in_vol)
>a unique per-drive/share hash. */
>if (ffvi_buf.ffvi.VolumeSerialNumber == 0)
> {
> - UNICODE_STRING path_prefix;
> - WCHAR *p;
> -
> - if (upath->Buffer[5] == L':' && upath->Buffer[6] == L'\\')
> - p = upath->Buffer + 6;
> - else
> - {
> - /* We're expecting an UNC path. Move p to the backslash after
> - "\??\UNC\server\share" or the trailing NUL. */
> - p = upath->Buffer + 7; /* Skip "\??\UNC" */
> - int bs_cnt = 0;
> -
> - while (*++p)
> - if (*p == L'\\')
> - if (++bs_cnt > 1)
> - break;
> - }
> - RtlInitCountedUnicodeString (&path_prefix, upath->Buffer,
> -(p - upath->Buffer) * sizeof (WCHAR));
> - ffvi_buf.ffvi.VolumeSerialNumber = hash_path_name ((ino_t) 0,
> - &path_prefix);
> + ffvi_buf.ffvi.VolumeSerialNumber = hash_prefix(upath);
Please note that we did this *only* for border case FSes returning a VSN
of 0. This was sufficient for these cases, but not in a a general sense.
Corinna
[PATCH 09/11] mount.cc: Implement poor-man's cache
Try to avoid NtQueryVolumeInformationFile.
---
winsup/cygwin/mount.cc | 78 --
winsup/cygwin/mount.h | 2 +-
winsup/cygwin/path.cc | 2 +-
winsup/cygwin/path.h | 1 +
4 files changed, 56 insertions(+), 27 deletions(-)
diff --git a/winsup/cygwin/mount.cc b/winsup/cygwin/mount.cc
index e0349815d..1d2b3a61a 100644
--- a/winsup/cygwin/mount.cc
+++ b/winsup/cygwin/mount.cc
@@ -82,6 +82,32 @@ win32_device_name (const char *src_path, char *win32_path,
device& dev)
return true;
}
+static uint32_t
+hash_prefix (const PUNICODE_STRING upath)
+{
+ UNICODE_STRING prefix;
+ WCHAR *p;
+
+ if (upath->Buffer[5] == L':' && upath->Buffer[6] == L'\\')
+p = upath->Buffer + 6;
+ else
+{
+ /* We're expecting an UNC path. Move p to the backslash after
+ "\??\UNC\server\share" or the trailing NUL. */
+ p = upath->Buffer + 7; /* Skip "\??\UNC" */
+ int bs_cnt = 0;
+
+ while (*++p)
+if (*p == L'\\')
+ if (++bs_cnt > 1)
+break;
+}
+ RtlInitCountedUnicodeString (&prefix, upath->Buffer,
+ (p - upath->Buffer) * sizeof(WCHAR));
+
+ return hash_path_name ((ino_t) 0, &prefix);
+}
+
/* Beginning with Samba 3.0.28a, Samba allows to get version information using
the ExtendedInfo member returned by a FileFsObjectIdInformation request.
We just store the samba_version information for now. Older versions than
@@ -106,14 +132,16 @@ class fs_info_cache
struct {
fs_info fsi;
uint32_t hash;
+uint32_t prefix_hash;
} entry[MAX_FS_INFO_CNT];
uint32_t genhash (PFILE_FS_VOLUME_INFORMATION);
public:
fs_info_cache () : count (0) { fsi_lock.init ("fsi_lock"); }
+ fs_info *search (uint32_t);
fs_info *search (PFILE_FS_VOLUME_INFORMATION, uint32_t &);
- void add (uint32_t, fs_info *);
+ void add (uint32_t, fs_info *, uint32_t);
};
static fs_info_cache fsi_cache;
@@ -142,22 +170,31 @@ fs_info_cache::search (PFILE_FS_VOLUME_INFORMATION pffvi,
uint32_t &hash)
return &entry[i].fsi;
return NULL;
}
+fs_info*
+fs_info_cache::search (uint32_t prefix_hash)
+{
+ for (uint32_t i = 0; i < count; ++i)
+if (entry[i].prefix_hash == prefix_hash)
+ return &entry[i].fsi;
+ return NULL;
+}
void
-fs_info_cache::add (uint32_t hashval, fs_info *new_fsi)
+fs_info_cache::add (uint32_t hashval, fs_info *new_fsi, uint32_t prefix_hash)
{
fsi_lock.acquire ();
if (count < MAX_FS_INFO_CNT)
{
entry[count].fsi = *new_fsi;
entry[count].hash = hashval;
+ entry[count].prefix_hash = prefix_hash;
++count;
}
fsi_lock.release ();
}
bool
-fs_info::update (PUNICODE_STRING upath, HANDLE in_vol)
+fs_info::update (PUNICODE_STRING upath, HANDLE in_vol, bool use_prefix_hash)
{
NTSTATUS status = STATUS_OBJECT_NAME_NOT_FOUND;
HANDLE vol;
@@ -178,6 +215,17 @@ fs_info::update (PUNICODE_STRING upath, HANDLE in_vol)
UNICODE_STRING fsname;
clear ();
+
+ if (use_prefix_hash)
+{
+ fs_info *fsi = fsi_cache.search (hash_prefix (upath));
+ if (fsi)
+{
+ *this = *fsi;
+ return true;
+}
+}
+
/* Always caseinsensitive. We really just need access to the drive. */
InitializeObjectAttributes (&attr, upath, OBJ_CASE_INSENSITIVE, NULL, NULL);
if (in_vol)
@@ -233,27 +281,7 @@ fs_info::update (PUNICODE_STRING upath, HANDLE in_vol)
a unique per-drive/share hash. */
if (ffvi_buf.ffvi.VolumeSerialNumber == 0)
{
- UNICODE_STRING path_prefix;
- WCHAR *p;
-
- if (upath->Buffer[5] == L':' && upath->Buffer[6] == L'\\')
- p = upath->Buffer + 6;
- else
- {
- /* We're expecting an UNC path. Move p to the backslash after
-"\??\UNC\server\share" or the trailing NUL. */
- p = upath->Buffer + 7; /* Skip "\??\UNC" */
- int bs_cnt = 0;
-
- while (*++p)
- if (*p == L'\\')
- if (++bs_cnt > 1)
- break;
- }
- RtlInitCountedUnicodeString (&path_prefix, upath->Buffer,
- (p - upath->Buffer) * sizeof (WCHAR));
- ffvi_buf.ffvi.VolumeSerialNumber = hash_path_name ((ino_t) 0,
-&path_prefix);
+ ffvi_buf.ffvi.VolumeSerialNumber = hash_prefix(upath);
}
fs_info *fsi = fsi_cache.search (&ffvi_buf.ffvi, hash);
if (fsi)
@@ -460,7 +488,7 @@ fs_info::update (PUNICODE_STRING upath, HANDLE in_vol)
if (!in_vol)
NtClose (vol);
- fsi_cache.add (hash, this);
+ fsi_cache.add (hash, this, hash_prefix (upath));
return true;
}
diff --git a/winsup/cygwin/mount.h b/winsup/cygwin/mount.h
index 122a679a8..86b72fb4c 100644
--- a/winsup/cygwin/mount.h
+++ b/winsup/cygwin/mount.h
@@ -124,7 +124,7 @@ class fs_info
const char *fsname () const { return fsn[0] ? f
