Re: [PATCH v6 08/33] exec: allow memory to be allocated from any kind of path

[Xiao Guangrong]

On 11/09/2015 06:39 PM, Michael S. Tsirkin wrote:

On Fri, Oct 30, 2015 at 01:56:02PM +0800, Xiao Guangrong wrote:

Currently file_ram_alloc() is designed for hugetlbfs, however, the memory
of nvdimm can come from either raw pmem device eg, /dev/pmem, or the file
locates at DAX enabled filesystem

So this patch let it work on any kind of path

Signed-off-by: Xiao Guangrong 


So this allows regular memory to be specified directly.
This needs to be split out and merged separately
from acpi/nvdimm bits.


Yup, that is in my plan.



Alternatively, if it's possible to use nvdimm with DAX fs
(similar to hugetlbfs), leave these patches off for now.



DAX is a filesystem mount options, it is not easy to get this
info from a file.




---
  exec.c | 56 +---
  1 file changed, 17 insertions(+), 39 deletions(-)

diff --git a/exec.c b/exec.c
index 8af2570..3ca7e50 100644
--- a/exec.c
+++ b/exec.c
@@ -1174,32 +1174,6 @@ void qemu_mutex_unlock_ramlist(void)
  }

  #ifdef __linux__
-
-#include 
-
-#define HUGETLBFS_MAGIC   0x958458f6
-
-static long gethugepagesize(const char *path, Error **errp)
-{
-struct statfs fs;
-int ret;
-
-do {
-ret = statfs(path, );
-} while (ret != 0 && errno == EINTR);
-
-if (ret != 0) {
-error_setg_errno(errp, errno, "failed to get page size of file %s",
- path);
-return 0;
-}
-
-if (fs.f_type != HUGETLBFS_MAGIC)
-fprintf(stderr, "Warning: path not on HugeTLBFS: %s\n", path);
-
-return fs.f_bsize;
-}
-
  static void *file_ram_alloc(RAMBlock *block,
  ram_addr_t memory,
  const char *path,
@@ -1210,20 +1184,24 @@ static void *file_ram_alloc(RAMBlock *block,
  char *c;
  void *area;
  int fd;
-uint64_t hpagesize;
-Error *local_err = NULL;
+uint64_t pagesize;

-hpagesize = gethugepagesize(path, _err);
-if (local_err) {
-error_propagate(errp, local_err);
+pagesize = qemu_file_get_page_size(path);
+if (!pagesize) {
+error_setg(errp, "can't get page size for %s", path);
  goto error;
  }
-block->mr->align = hpagesize;

-if (memory < hpagesize) {
+if (pagesize == getpagesize()) {
+fprintf(stderr, "Memory is not allocated from HugeTlbfs.\n");
+}
+
+block->mr->align = pagesize;
+
+if (memory < pagesize) {
  error_setg(errp, "memory size 0x" RAM_ADDR_FMT " must be equal to "
-   "or larger than huge page size 0x%" PRIx64,
-   memory, hpagesize);
+   "or larger than page size 0x%" PRIx64,
+   memory, pagesize);
  goto error;
  }

@@ -1247,14 +1225,14 @@ static void *file_ram_alloc(RAMBlock *block,
  fd = mkstemp(filename);
  if (fd < 0) {
  error_setg_errno(errp, errno,
- "unable to create backing store for hugepages");
+ "unable to create backing store for path %s", path);
  g_free(filename);
  goto error;
  }
  unlink(filename);
  g_free(filename);


Looks like we are still calling mkstemp/unlink here.
How does this work?


Hmm? We have got the fd so the file can be safely unlinked (kernel does not 
actually unlink
the file since mkstemp() holds a refcount.).

And this patch just renames the variables, no logic changed. Will drop it from 
the serials
for now on.
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Re: [PATCH v6 08/33] exec: allow memory to be allocated from any kind of path

[Michael S. Tsirkin]

On Fri, Oct 30, 2015 at 01:56:02PM +0800, Xiao Guangrong wrote:
> Currently file_ram_alloc() is designed for hugetlbfs, however, the memory
> of nvdimm can come from either raw pmem device eg, /dev/pmem, or the file
> locates at DAX enabled filesystem
> 
> So this patch let it work on any kind of path
> 
> Signed-off-by: Xiao Guangrong 

So this allows regular memory to be specified directly.
This needs to be split out and merged separately
from acpi/nvdimm bits.

Alternatively, if it's possible to use nvdimm with DAX fs
(similar to hugetlbfs), leave these patches off for now.


> ---
>  exec.c | 56 +---
>  1 file changed, 17 insertions(+), 39 deletions(-)
> 
> diff --git a/exec.c b/exec.c
> index 8af2570..3ca7e50 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -1174,32 +1174,6 @@ void qemu_mutex_unlock_ramlist(void)
>  }
>  
>  #ifdef __linux__
> -
> -#include 
> -
> -#define HUGETLBFS_MAGIC   0x958458f6
> -
> -static long gethugepagesize(const char *path, Error **errp)
> -{
> -struct statfs fs;
> -int ret;
> -
> -do {
> -ret = statfs(path, );
> -} while (ret != 0 && errno == EINTR);
> -
> -if (ret != 0) {
> -error_setg_errno(errp, errno, "failed to get page size of file %s",
> - path);
> -return 0;
> -}
> -
> -if (fs.f_type != HUGETLBFS_MAGIC)
> -fprintf(stderr, "Warning: path not on HugeTLBFS: %s\n", path);
> -
> -return fs.f_bsize;
> -}
> -
>  static void *file_ram_alloc(RAMBlock *block,
>  ram_addr_t memory,
>  const char *path,
> @@ -1210,20 +1184,24 @@ static void *file_ram_alloc(RAMBlock *block,
>  char *c;
>  void *area;
>  int fd;
> -uint64_t hpagesize;
> -Error *local_err = NULL;
> +uint64_t pagesize;
>  
> -hpagesize = gethugepagesize(path, _err);
> -if (local_err) {
> -error_propagate(errp, local_err);
> +pagesize = qemu_file_get_page_size(path);
> +if (!pagesize) {
> +error_setg(errp, "can't get page size for %s", path);
>  goto error;
>  }
> -block->mr->align = hpagesize;
>  
> -if (memory < hpagesize) {
> +if (pagesize == getpagesize()) {
> +fprintf(stderr, "Memory is not allocated from HugeTlbfs.\n");
> +}
> +
> +block->mr->align = pagesize;
> +
> +if (memory < pagesize) {
>  error_setg(errp, "memory size 0x" RAM_ADDR_FMT " must be equal to "
> -   "or larger than huge page size 0x%" PRIx64,
> -   memory, hpagesize);
> +   "or larger than page size 0x%" PRIx64,
> +   memory, pagesize);
>  goto error;
>  }
>  
> @@ -1247,14 +1225,14 @@ static void *file_ram_alloc(RAMBlock *block,
>  fd = mkstemp(filename);
>  if (fd < 0) {
>  error_setg_errno(errp, errno,
> - "unable to create backing store for hugepages");
> + "unable to create backing store for path %s", path);
>  g_free(filename);
>  goto error;
>  }
>  unlink(filename);
>  g_free(filename);

Looks like we are still calling mkstemp/unlink here.
How does this work?

>  
> -memory = ROUND_UP(memory, hpagesize);
> +memory = ROUND_UP(memory, pagesize);
>  
>  /*
>   * ftruncate is not supported by hugetlbfs in older
> @@ -1266,10 +1244,10 @@ static void *file_ram_alloc(RAMBlock *block,
>  perror("ftruncate");
>  }
>  
> -area = qemu_ram_mmap(fd, memory, hpagesize, block->flags & RAM_SHARED);
> +area = qemu_ram_mmap(fd, memory, pagesize, block->flags & RAM_SHARED);
>  if (area == MAP_FAILED) {
>  error_setg_errno(errp, errno,
> - "unable to map backing store for hugepages");
> + "unable to map backing store for path %s", path);
>  close(fd);
>  goto error;
>  }
> -- 
> 1.8.3.1
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