[PATCH v3] Retry Large Buffer Allocations
Artem Bityutskiy
dedekind1 at gmail.com
Thu Apr 7 04:13:03 EDT 2011
On Wed, 2011-04-06 at 08:56 -0700, Grant Erickson wrote:
> When handling user space read or write requests via mtd_{read,write}
> or JFFS2 medium scan requests, exponentially back off on the size of
> the requested kernel transfer buffer until it succeeds or until the
> requested transfer buffer size falls below the page size.
>
> This helps ensure the operation can succeed under low-memory,
> highly-fragmented situations albeit somewhat more slowly.
>
> v2: Incorporated coding style and comment feedback from Artem.
> v3: Incorporated more feedback from Artem. Retargeted patch against
> l2-mtd-2.6.
>
> Signed-off-by: Grant Erickson <marathon96 at gmail.com>
Looks good, but I have 2 requests still.
> ---
> drivers/mtd/mtdchar.c | 50 +++++++++++++++++++++-------------------------
> drivers/mtd/mtdcore.c | 41 ++++++++++++++++++++++++++++++++++++++
> fs/jffs2/scan.c | 11 +++++----
> include/linux/mtd/mtd.h | 2 +
> 4 files changed, 72 insertions(+), 32 deletions(-)
>
> diff --git a/drivers/mtd/mtdchar.c b/drivers/mtd/mtdchar.c
> index 145b3d0d..8651a79 100644
> --- a/drivers/mtd/mtdchar.c
> +++ b/drivers/mtd/mtdchar.c
> @@ -166,10 +166,23 @@ static int mtd_close(struct inode *inode, struct file *file)
> return 0;
> } /* mtd_close */
>
> -/* FIXME: This _really_ needs to die. In 2.5, we should lock the
> - userspace buffer down and use it directly with readv/writev.
> -*/
> -#define MAX_KMALLOC_SIZE 0x20000
> +/* Back in April 2005, Linus wrote:
> + *
> + * FIXME: This _really_ needs to die. In 2.5, we should lock the
> + * userspace buffer down and use it directly with readv/writev.
> + *
> + * The implementation below, using mtd_alloc_up_to, mitigates
1. s/mtd_alloc_up_to/mtd_kmalloc_up_to/ here as well.
BTW, It still does not apply on top of l2-mtd-2.6.git, the conflict is
in include/linux/mtd/mtd.h - but well, I can fix that conflict.
2. Please, fix compilation warning:
fs/jffs2/scan.c: In function ‘jffs2_scan_medium’:
fs/jffs2/scan.c:123: warning: passing argument 1 of ‘mtd_kmalloc_up_to’ from incompatible pointer type
include/linux/mtd/mtd.h:351: note: expected ‘size_t *’ but argument is of type ‘uint32_t *’
This is a bug in 64-bit machines because sizeof(size_t) is 8 there.
Could you please fix that, test, and then send the final version.
Thanks!
--
Best Regards,
Artem Bityutskiy (Артём Битюцкий)
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