[U-Boot] [PATCH v1] fs: fat: dynamically allocate memory for temporary buffer

[U-Boot] [PATCH v1] fs: fat: dynamically allocate memory for temporary buffer

[Stefan Agner]

From: Stefan Agner <stefan.agner@toradex.com>

Drop the statically allocated get_contents_vfatname_block and
dynamically allocate a buffer only if required. This saves
64KiB of memory.

Signed-off-by: Stefan Agner <stefan.agner@toradex.com>
---

 fs/fat/fat.c | 20 ++++++++++++++------
 1 file changed, 14 insertions(+), 6 deletions(-)

diff --git a/fs/fat/fat.c b/fs/fat/fat.c
index 4bc3030ab8..06bcd02835 100644
--- a/fs/fat/fat.c
+++ b/fs/fat/fat.c
@@ -305,9 +305,6 @@ get_cluster(fsdata *mydata, __u32 clustnum, __u8 *buffer, unsigned long size)
  * into 'buffer'.
  * Update the number of bytes read in *gotsize or return -1 on fatal errors.
  */
-__u8 get_contents_vfatname_block[MAX_CLUSTSIZE]
-	__aligned(ARCH_DMA_MINALIGN);
-
 static int get_contents(fsdata *mydata, dir_entry *dentptr, loff_t pos,
 			__u8 *buffer, loff_t maxsize, loff_t *gotsize)
 {
@@ -318,7 +315,7 @@ static int get_contents(fsdata *mydata, dir_entry *dentptr, loff_t pos,
 	loff_t actsize;
 
 	*gotsize = 0;
-	debug("Filesize: %llu bytes\n", filesize);
+	debug("Filesize: %llu bytes, starting at pos %llu\n", filesize, pos);
 
 	if (pos >= filesize) {
 		debug("Read position past EOF: %llu\n", pos);
@@ -350,15 +347,26 @@ static int get_contents(fsdata *mydata, dir_entry *dentptr, loff_t pos,
 
 	/* align to beginning of next cluster if any */
 	if (pos) {
+		__u8 *tmp_buffer;
+
+		tmp_buffer = malloc_cache_aligned(MAX_CLUSTSIZE);
+		if (tmp_buffer == NULL) {
+			debug("Error: allocating buffer\n");
+			return -1;
+		}
+
 		actsize = min(filesize, (loff_t)bytesperclust);
-		if (get_cluster(mydata, curclust, get_contents_vfatname_block,
+		if (get_cluster(mydata, curclust, tmp_buffer,
 				(int)actsize) != 0) {
 			printf("Error reading cluster\n");
+			free(tmp_buffer);
 			return -1;
 		}
 		filesize -= actsize;
 		actsize -= pos;
-		memcpy(buffer, get_contents_vfatname_block + pos, actsize);
+		memcpy(tmp_buffer, buffer + pos, actsize);
+		free(tmp_buffer);
+
 		*gotsize += actsize;
 		if (!filesize)
 			return 0;
-- 
2.19.2

[U-Boot] [PATCH v1] fs: fat: dynamically allocate memory for temporary buffer

[Lukasz Majewski]

On Thu,  6 Dec 2018 14:58:52 +0100
Stefan Agner <stefan@agner.ch> wrote:

> From: Stefan Agner <stefan.agner@toradex.com>
> 
> Drop the statically allocated get_contents_vfatname_block and
> dynamically allocate a buffer only if required. This saves
> 64KiB of memory.
> 
> Signed-off-by: Stefan Agner <stefan.agner@toradex.com>
> ---
> 
>  fs/fat/fat.c | 20 ++++++++++++++------
>  1 file changed, 14 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/fat/fat.c b/fs/fat/fat.c
> index 4bc3030ab8..06bcd02835 100644
> --- a/fs/fat/fat.c
> +++ b/fs/fat/fat.c
> @@ -305,9 +305,6 @@ get_cluster(fsdata *mydata, __u32 clustnum, __u8
> *buffer, unsigned long size)
>   * into 'buffer'.
>   * Update the number of bytes read in *gotsize or return -1 on fatal
> errors. */
> -__u8 get_contents_vfatname_block[MAX_CLUSTSIZE]
> -	__aligned(ARCH_DMA_MINALIGN);
> -
>  static int get_contents(fsdata *mydata, dir_entry *dentptr, loff_t
> pos, __u8 *buffer, loff_t maxsize, loff_t *gotsize)
>  {
> @@ -318,7 +315,7 @@ static int get_contents(fsdata *mydata, dir_entry
> *dentptr, loff_t pos, loff_t actsize;
>  
>  	*gotsize = 0;
> -	debug("Filesize: %llu bytes\n", filesize);
> +	debug("Filesize: %llu bytes, starting at pos %llu\n",
> filesize, pos); 
>  	if (pos >= filesize) {
>  		debug("Read position past EOF: %llu\n", pos);
> @@ -350,15 +347,26 @@ static int get_contents(fsdata *mydata,
> dir_entry *dentptr, loff_t pos, 
>  	/* align to beginning of next cluster if any */
>  	if (pos) {
> +		__u8 *tmp_buffer;
> +
> +		tmp_buffer = malloc_cache_aligned(MAX_CLUSTSIZE);
> +		if (tmp_buffer == NULL) {
> +			debug("Error: allocating buffer\n");
> +			return -1;
> +		}
> +
>  		actsize = min(filesize, (loff_t)bytesperclust);
> -		if (get_cluster(mydata, curclust,
> get_contents_vfatname_block,
> +		if (get_cluster(mydata, curclust, tmp_buffer,
>  				(int)actsize) != 0) {
>  			printf("Error reading cluster\n");
> +			free(tmp_buffer);
>  			return -1;
>  		}
>  		filesize -= actsize;
>  		actsize -= pos;
> -		memcpy(buffer, get_contents_vfatname_block + pos,
> actsize);
> +		memcpy(tmp_buffer, buffer + pos, actsize);
> +		free(tmp_buffer);
> +
>  		*gotsize += actsize;
>  		if (!filesize)
>  			return 0;

Reviewed-by: Lukasz Majewski <lukma@denx.de>


Best regards,

Lukasz Majewski

--

DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany
Phone: (+49)-8142-66989-59 Fax: (+49)-8142-66989-80 Email: lukma at denx.de
-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 488 bytes
Desc: OpenPGP digital signature
URL: <http://lists.denx.de/pipermail/u-boot/attachments/20181206/7c37379d/attachment.sig>

[U-Boot] [PATCH v1] fs: fat: dynamically allocate memory for temporary buffer

[Tom Rini]

On Thu, Dec 06, 2018 at 02:58:52PM +0100, Stefan Agner wrote:

> From: Stefan Agner <stefan.agner@toradex.com>
> 
> Drop the statically allocated get_contents_vfatname_block and
> dynamically allocate a buffer only if required. This saves
> 64KiB of memory.
> 
> Signed-off-by: Stefan Agner <stefan.agner@toradex.com>

Is there a particular issue you're running into here, or just that what
we're doing is just generally not a great idea?  I ask since I need to
poke git history to make sure that the thing at the back of my mind
about us needing to do this for some annoying boot case is intentional.
Thanks!

-- 
Tom
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 819 bytes
Desc: not available
URL: <http://lists.denx.de/pipermail/u-boot/attachments/20181206/8781326a/attachment.sig>

[U-Boot] [PATCH v1] fs: fat: dynamically allocate memory for temporary buffer

[Stefan Agner]

On 06.12.2018 16:13, Tom Rini wrote:
> On Thu, Dec 06, 2018 at 02:58:52PM +0100, Stefan Agner wrote:
> 
>> From: Stefan Agner <stefan.agner@toradex.com>
>>
>> Drop the statically allocated get_contents_vfatname_block and
>> dynamically allocate a buffer only if required. This saves
>> 64KiB of memory.
>>
>> Signed-off-by: Stefan Agner <stefan.agner@toradex.com>
> 
> Is there a particular issue you're running into here, or just that what
> we're doing is just generally not a great idea?  I ask since I need to
> poke git history to make sure that the thing at the back of my mind
> about us needing to do this for some annoying boot case is intentional.

I was in the process checking large global variables since I had issues
on a target with limited SRAM (used pre-relocation). I only after
writing this patch I realized that the space for the .bss section is not
required pre-relocation, so the patch did not help in my particular
case.

That said, in git history I saw that get_contents_vfatname_block has
been used more broadly in earlier FAT implementations. Now it is only
used to handle a corner case: when loading from a file with an offset...
I guess the .bss section is cleared, so we probably safe 64KiB of
zeroing out... I feel it is still worth doing the change, but I don't
have a really strong feeling.

--
Stefan

[U-Boot] [PATCH v1] fs: fat: dynamically allocate memory for temporary buffer

[Tom Rini]

On Thu, Dec 06, 2018 at 04:45:08PM +0100, Stefan Agner wrote:
> On 06.12.2018 16:13, Tom Rini wrote:
> > On Thu, Dec 06, 2018 at 02:58:52PM +0100, Stefan Agner wrote:
> > 
> >> From: Stefan Agner <stefan.agner@toradex.com>
> >>
> >> Drop the statically allocated get_contents_vfatname_block and
> >> dynamically allocate a buffer only if required. This saves
> >> 64KiB of memory.
> >>
> >> Signed-off-by: Stefan Agner <stefan.agner@toradex.com>
> > 
> > Is there a particular issue you're running into here, or just that what
> > we're doing is just generally not a great idea?  I ask since I need to
> > poke git history to make sure that the thing at the back of my mind
> > about us needing to do this for some annoying boot case is intentional.
> 
> I was in the process checking large global variables since I had issues
> on a target with limited SRAM (used pre-relocation). I only after
> writing this patch I realized that the space for the .bss section is not
> required pre-relocation, so the patch did not help in my particular
> case.
> 
> That said, in git history I saw that get_contents_vfatname_block has
> been used more broadly in earlier FAT implementations. Now it is only
> used to handle a corner case: when loading from a file with an offset...
> I guess the .bss section is cleared, so we probably safe 64KiB of
> zeroing out... I feel it is still worth doing the change, but I don't
> have a really strong feeling.

Thanks for checking.  Yes, this is probably a good thing to do overall
and whatever historical reason we needed it like this isn't applicable
now if we're doing offset loading only in this case which isn't an SPL
thing anyhow.

-- 
Tom
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 819 bytes
Desc: not available
URL: <http://lists.denx.de/pipermail/u-boot/attachments/20181206/134eabdf/attachment.sig>

[U-Boot] [PATCH v1] fs: fat: dynamically allocate memory for temporary buffer

[Stefan Agner]

On 06.12.2018 14:58, Stefan Agner wrote:
> From: Stefan Agner <stefan.agner@toradex.com>
> 
> Drop the statically allocated get_contents_vfatname_block and
> dynamically allocate a buffer only if required. This saves
> 64KiB of memory.
> 
> Signed-off-by: Stefan Agner <stefan.agner@toradex.com>
> ---
> 
>  fs/fat/fat.c | 20 ++++++++++++++------
>  1 file changed, 14 insertions(+), 6 deletions(-)
> 
> diff --git a/fs/fat/fat.c b/fs/fat/fat.c
> index 4bc3030ab8..06bcd02835 100644
> --- a/fs/fat/fat.c
> +++ b/fs/fat/fat.c
> @@ -305,9 +305,6 @@ get_cluster(fsdata *mydata, __u32 clustnum, __u8
> *buffer, unsigned long size)
>   * into 'buffer'.
>   * Update the number of bytes read in *gotsize or return -1 on fatal errors.
>   */
> -__u8 get_contents_vfatname_block[MAX_CLUSTSIZE]
> -	__aligned(ARCH_DMA_MINALIGN);
> -
>  static int get_contents(fsdata *mydata, dir_entry *dentptr, loff_t pos,
>  			__u8 *buffer, loff_t maxsize, loff_t *gotsize)
>  {
> @@ -318,7 +315,7 @@ static int get_contents(fsdata *mydata, dir_entry
> *dentptr, loff_t pos,
>  	loff_t actsize;
>  
>  	*gotsize = 0;
> -	debug("Filesize: %llu bytes\n", filesize);
> +	debug("Filesize: %llu bytes, starting at pos %llu\n", filesize, pos);
>  
>  	if (pos >= filesize) {
>  		debug("Read position past EOF: %llu\n", pos);
> @@ -350,15 +347,26 @@ static int get_contents(fsdata *mydata,
> dir_entry *dentptr, loff_t pos,
>  
>  	/* align to beginning of next cluster if any */
>  	if (pos) {
> +		__u8 *tmp_buffer;
> +
> +		tmp_buffer = malloc_cache_aligned(MAX_CLUSTSIZE);
> +		if (tmp_buffer == NULL) {
> +			debug("Error: allocating buffer\n");
> +			return -1;
> +		}
> +
>  		actsize = min(filesize, (loff_t)bytesperclust);
> -		if (get_cluster(mydata, curclust, get_contents_vfatname_block,
> +		if (get_cluster(mydata, curclust, tmp_buffer,
>  				(int)actsize) != 0) {
>  			printf("Error reading cluster\n");
> +			free(tmp_buffer);
>  			return -1;
>  		}
>  		filesize -= actsize;
>  		actsize -= pos;
> -		memcpy(buffer, get_contents_vfatname_block + pos, actsize);
> +		memcpy(tmp_buffer, buffer + pos, actsize);

I somehow managed to mix up copy direction here. Will send a v2.

--
Stefan

> +		free(tmp_buffer);
> +
>  		*gotsize += actsize;
>  		if (!filesize)
>  			return 0;