Messages in this thread Patch in this message | | | Date | Thu, 11 Nov 2004 19:22:16 +0300 | From | Kirill Korotaev <> | Subject | [PATCH]: 4/4GB: Ineffiecency in filemap.c |
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This patch fixes ineffiecency in copying user data in some code pieces when 4GB split is ON: filemap.c tries to call __copy_XXX_user while in atomic, but 4GB split code always fails copying when in atomic. So this optimization for normal kernels doesn't work with 4GB split, moreover, makes lot's of unnessaccary locks/checks.
Signed-Off-By: Kirill Korotaev <dev@sw.ru>
Kirill
P.S. These 4GB split patches are against modified 2.6.8.1 kernel, but should be appliable to last Fedora kernels --- ./mm/filemap.c.4gbcptusr 2004-11-10 18:38:19.000000000 +0300 +++ ./mm/filemap.c 2004-11-11 16:34:24.669739800 +0300 @@ -814,6 +814,7 @@ int file_read_actor(read_descriptor_t *d if (size > count) size = count; +#ifndef CONFIG_X86_UACCESS_INDIRECT /* * Faults on the destination of a read are common, so do it before * taking the kmap. @@ -822,20 +823,23 @@ int file_read_actor(read_descriptor_t *d kaddr = kmap_atomic(page, KM_USER0); left = __copy_to_user(desc->arg.buf, kaddr + offset, size); kunmap_atomic(kaddr, KM_USER0); - if (left == 0) - goto success; } +#else + left = size; +#endif - /* Do it the slow way */ - kaddr = kmap(page); - left = __copy_to_user(desc->arg.buf, kaddr + offset, size); - kunmap(page); - - if (left) { - size -= left; - desc->error = -EFAULT; + if (left != 0) { + /* Do it the slow way */ + kaddr = kmap(page); + left = __copy_to_user(desc->arg.buf, kaddr + offset, size); + kunmap(page); + + if (left) { + size -= left; + desc->error = -EFAULT; + } } -success: + desc->count = count - size; desc->written += size; desc->arg.buf += size; @@ -1615,9 +1619,13 @@ filemap_copy_from_user(struct page *page char *kaddr; int left; +#ifndef CONFIG_X86_UACCESS_INDIRECT kaddr = kmap_atomic(page, KM_USER0); left = __copy_from_user(kaddr + offset, buf, bytes); kunmap_atomic(kaddr, KM_USER0); +#else + left = bytes; +#endif if (left != 0) { /* Do it the slow way */ @@ -1668,10 +1676,14 @@ filemap_copy_from_user_iovec(struct page char *kaddr; size_t copied; +#ifndef CONFIG_X86_UACCESS_INDIRECT kaddr = kmap_atomic(page, KM_USER0); copied = __filemap_copy_from_user_iovec(kaddr + offset, iov, base, bytes); kunmap_atomic(kaddr, KM_USER0); +#else + copied = 0; +#endif if (copied != bytes) { kaddr = kmap(page); copied = __filemap_copy_from_user_iovec(kaddr + offset, iov, --- ./mm/shmem.c.4gbcptusr 2004-11-10 18:38:19.000000000 +0300 +++ ./mm/shmem.c 2004-11-11 14:21:39.919565872 +0300 @@ -1322,6 +1322,7 @@ shmem_file_write(struct file *file, cons break; left = bytes; +#ifndef CONFIG_X86_UACCESS_INDIRECT if (PageHighMem(page)) { volatile unsigned char dummy; __get_user(dummy, buf); @@ -1331,6 +1332,7 @@ shmem_file_write(struct file *file, cons left = __copy_from_user(kaddr + offset, buf, bytes); kunmap_atomic(kaddr, KM_USER0); } +#endif if (left) { kaddr = kmap(page); left = __copy_from_user(kaddr + offset, buf, bytes); | |