diff options
Diffstat (limited to 'drivers/mtd/mtdcore.c')
| -rw-r--r-- | drivers/mtd/mtdcore.c | 49 |
1 files changed, 49 insertions, 0 deletions
diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c index da69bc8a5a7..a50348b60d7 100644 --- a/drivers/mtd/mtdcore.c +++ b/drivers/mtd/mtdcore.c @@ -638,6 +638,54 @@ int default_mtd_writev(struct mtd_info *mtd, const struct kvec *vecs, return ret; } +/** + * mtd_kmalloc_up_to - allocate a contiguous buffer up to the specified size + * @size: A pointer to the ideal or maximum size of the allocation. Points + * to the actual allocation size on success. + * + * This routine attempts to allocate a contiguous kernel buffer up to + * the specified size, backing off the size of the request exponentially + * until the request succeeds or until the allocation size falls below + * the system page size. This attempts to make sure it does not adversely + * impact system performance, so when allocating more than one page, we + * ask the memory allocator to avoid re-trying, swapping, writing back + * or performing I/O. + * + * Note, this function also makes sure that the allocated buffer is aligned to + * the MTD device's min. I/O unit, i.e. the "mtd->writesize" value. + * + * This is called, for example by mtd_{read,write} and jffs2_scan_medium, + * to handle smaller (i.e. degraded) buffer allocations under low- or + * fragmented-memory situations where such reduced allocations, from a + * requested ideal, are allowed. + * + * Returns a pointer to the allocated buffer on success; otherwise, NULL. + */ +void *mtd_kmalloc_up_to(const struct mtd_info *mtd, size_t *size) +{ + gfp_t flags = __GFP_NOWARN | __GFP_WAIT | + __GFP_NORETRY | __GFP_NO_KSWAPD; + size_t min_alloc = max_t(size_t, mtd->writesize, PAGE_SIZE); + void *kbuf; + + *size = min_t(size_t, *size, KMALLOC_MAX_SIZE); + + while (*size > min_alloc) { + kbuf = kmalloc(*size, flags); + if (kbuf) + return kbuf; + + *size >>= 1; + *size = ALIGN(*size, mtd->writesize); + } + + /* + * For the last resort allocation allow 'kmalloc()' to do all sorts of + * things (write-back, dropping caches, etc) by using GFP_KERNEL. + */ + return kmalloc(*size, GFP_KERNEL); +} + EXPORT_SYMBOL_GPL(add_mtd_device); EXPORT_SYMBOL_GPL(del_mtd_device); EXPORT_SYMBOL_GPL(get_mtd_device); @@ -648,6 +696,7 @@ EXPORT_SYMBOL_GPL(__put_mtd_device); EXPORT_SYMBOL_GPL(register_mtd_user); EXPORT_SYMBOL_GPL(unregister_mtd_user); EXPORT_SYMBOL_GPL(default_mtd_writev); +EXPORT_SYMBOL_GPL(mtd_kmalloc_up_to); #ifdef CONFIG_PROC_FS |