[PATCH 1/2] BDI: Provide backing device capability information [try #3]
From: David Howells
Date: Tue Mar 08 2005 - 09:17:32 EST
The attached patch replaces backing_dev_info::memory_backed with capabilitied
bitmap. The capabilities available include:
(*) BDI_CAP_NO_ACCT_DIRTY
Set if the pages associated with this backing device should not be
tracked by the dirty page accounting.
(*) BDI_CAP_NO_WRITEBACK
Set if dirty pages associated with this backing device should not have
writepage() or writepages() invoked upon them to clean them.
(*) Capability markers that indicate what a backing device is capable of
with regard to memory mapping facilities. These flags indicate whether a
device can be mapped directly, whether it can be copied for a mapping,
and whether direct mappings can be read, written and/or executed. This
information is primarily aimed at improving no-MMU private mapping
support.
The patch also provides convenience functions for determining the dirty-page
capabilities available on backing devices directly or on the backing devices
associated with a mapping. These are provided to keep line length down when
checking for the capabilities.
Signed-Off-By: David Howells <dhowells@xxxxxxxxxx>
---
diff -uNrp /warthog/kernels/linux-2.6.11-rc4/include/linux/backing-dev.h linux-2.6.11-rc4-memback/include/linux/backing-dev.h
--- /warthog/kernels/linux-2.6.11-rc4/include/linux/backing-dev.h 2004-06-18 13:44:05.000000000 +0100
+++ linux-2.6.11-rc4-memback/include/linux/backing-dev.h 2005-03-08 11:03:45.000000000 +0000
@@ -25,13 +25,39 @@ typedef int (congested_fn)(void *, int);
struct backing_dev_info {
unsigned long ra_pages; /* max readahead in PAGE_CACHE_SIZE units */
unsigned long state; /* Always use atomic bitops on this */
- int memory_backed; /* Cannot clean pages with writepage */
+ unsigned int capabilities; /* Device capabilities */
congested_fn *congested_fn; /* Function pointer if device is md/dm */
void *congested_data; /* Pointer to aux data for congested func */
void (*unplug_io_fn)(struct backing_dev_info *, struct page *);
void *unplug_io_data;
};
+
+/*
+ * Flags in backing_dev_info::capability
+ * - The first two flags control whether dirty pages will contribute to the
+ * VM's accounting and whether writepages() should be called for dirty pages
+ * (something that would not, for example, be appropriate for ramfs)
+ * - These flags let !MMU mmap() govern direct device mapping vs immediate
+ * copying more easily for MAP_PRIVATE, especially for ROM filesystems
+ */
+#define BDI_CAP_NO_ACCT_DIRTY 0x00000001 /* Dirty pages shouldn't contribute to accounting */
+#define BDI_CAP_NO_WRITEBACK 0x00000002 /* Don't write pages back */
+#define BDI_CAP_MAP_COPY 0x00000004 /* Copy can be mapped (MAP_PRIVATE) */
+#define BDI_CAP_MAP_DIRECT 0x00000008 /* Can be mapped directly (MAP_SHARED) */
+#define BDI_CAP_READ_MAP 0x00000010 /* Can be mapped for reading */
+#define BDI_CAP_WRITE_MAP 0x00000020 /* Can be mapped for writing */
+#define BDI_CAP_EXEC_MAP 0x00000040 /* Can be mapped for execution */
+#define BDI_CAP_VMFLAGS \
+ (BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP)
+
+#if defined(VM_MAYREAD) && \
+ (BDI_CAP_READ_MAP != VM_MAYREAD || \
+ BDI_CAP_WRITE_MAP != VM_MAYWRITE || \
+ BDI_CAP_EXEC_MAP != VM_MAYEXEC)
+#error please change backing_dev_info::capabilities flags
+#endif
+
extern struct backing_dev_info default_backing_dev_info;
void default_unplug_io_fn(struct backing_dev_info *bdi, struct page *page);
@@ -62,4 +88,17 @@ static inline int bdi_rw_congested(struc
(1 << BDI_write_congested));
}
+#define bdi_cap_writeback_dirty(bdi) \
+ (!((bdi)->capabilities & BDI_CAP_NO_WRITEBACK))
+
+#define bdi_cap_account_dirty(bdi) \
+ (!((bdi)->capabilities & BDI_CAP_NO_ACCT_DIRTY))
+
+#define mapping_cap_writeback_dirty(mapping) \
+ bdi_cap_writeback_dirty((mapping)->backing_dev_info)
+
+#define mapping_cap_account_dirty(mapping) \
+ bdi_cap_account_dirty((mapping)->backing_dev_info)
+
+
#endif /* _LINUX_BACKING_DEV_H */
diff -uNrp /warthog/kernels/linux-2.6.11-rc4/drivers/block/ll_rw_blk.c linux-2.6.11-rc4-memback/drivers/block/ll_rw_blk.c
--- /warthog/kernels/linux-2.6.11-rc4/drivers/block/ll_rw_blk.c 2005-02-14 12:18:23.000000000 +0000
+++ linux-2.6.11-rc4-memback/drivers/block/ll_rw_blk.c 2005-03-08 11:09:54.000000000 +0000
@@ -238,7 +238,7 @@ void blk_queue_make_request(request_queu
q->make_request_fn = mfn;
q->backing_dev_info.ra_pages = (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
q->backing_dev_info.state = 0;
- q->backing_dev_info.memory_backed = 0;
+ q->backing_dev_info.capabilities = BDI_CAP_MAP_COPY;
blk_queue_max_sectors(q, MAX_SECTORS);
blk_queue_hardsect_size(q, 512);
blk_queue_dma_alignment(q, 511);
diff -uNrp /warthog/kernels/linux-2.6.11-rc4/drivers/block/rd.c linux-2.6.11-rc4-memback/drivers/block/rd.c
--- /warthog/kernels/linux-2.6.11-rc4/drivers/block/rd.c 2005-01-04 11:13:05.000000000 +0000
+++ linux-2.6.11-rc4-memback/drivers/block/rd.c 2005-03-08 11:14:00.000000000 +0000
@@ -325,7 +325,7 @@ static int rd_ioctl(struct inode *inode,
*/
static struct backing_dev_info rd_backing_dev_info = {
.ra_pages = 0, /* No readahead */
- .memory_backed = 1, /* Does not contribute to dirty memory */
+ .capabilities = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK | BDI_CAP_MAP_COPY,
.unplug_io_fn = default_unplug_io_fn,
};
@@ -336,7 +336,7 @@ static struct backing_dev_info rd_backin
*/
static struct backing_dev_info rd_file_backing_dev_info = {
.ra_pages = 0, /* No readahead */
- .memory_backed = 0, /* Does contribute to dirty memory */
+ .capabilities = BDI_CAP_MAP_COPY, /* Does contribute to dirty memory */
.unplug_io_fn = default_unplug_io_fn,
};
diff -uNrp /warthog/kernels/linux-2.6.11-rc4/drivers/char/mem.c linux-2.6.11-rc4-memback/drivers/char/mem.c
--- /warthog/kernels/linux-2.6.11-rc4/drivers/char/mem.c 2005-01-04 11:13:10.000000000 +0000
+++ linux-2.6.11-rc4-memback/drivers/char/mem.c 2005-03-08 11:15:19.000000000 +0000
@@ -23,6 +23,7 @@
#include <linux/devfs_fs_kernel.h>
#include <linux/ptrace.h>
#include <linux/device.h>
+#include <linux/backing-dev.h>
#include <asm/uaccess.h>
#include <asm/io.h>
@@ -613,6 +614,10 @@ static struct file_operations zero_fops
.mmap = mmap_zero,
};
+static struct backing_dev_info zero_bdi = {
+ .capabilities = BDI_CAP_MAP_COPY,
+};
+
static struct file_operations full_fops = {
.llseek = full_lseek,
.read = read_full,
@@ -659,6 +664,7 @@ static int memory_open(struct inode * in
break;
#endif
case 5:
+ filp->f_mapping->backing_dev_info = &zero_bdi;
filp->f_op = &zero_fops;
break;
case 7:
diff -uNrp /warthog/kernels/linux-2.6.11-rc4/fs/buffer.c linux-2.6.11-rc4-memback/fs/buffer.c
--- /warthog/kernels/linux-2.6.11-rc4/fs/buffer.c 2005-02-14 12:18:50.000000000 +0000
+++ linux-2.6.11-rc4-memback/fs/buffer.c 2005-03-07 13:25:05.000000000 +0000
@@ -876,7 +876,7 @@ int __set_page_dirty_buffers(struct page
if (!TestSetPageDirty(page)) {
spin_lock_irq(&mapping->tree_lock);
if (page->mapping) { /* Race with truncate? */
- if (!mapping->backing_dev_info->memory_backed)
+ if (mapping_cap_account_dirty(mapping))
inc_page_state(nr_dirty);
radix_tree_tag_set(&mapping->page_tree,
page_index(page),
diff -uNrp /warthog/kernels/linux-2.6.11-rc4/fs/fs-writeback.c linux-2.6.11-rc4-memback/fs/fs-writeback.c
--- /warthog/kernels/linux-2.6.11-rc4/fs/fs-writeback.c 2005-02-14 12:18:51.000000000 +0000
+++ linux-2.6.11-rc4-memback/fs/fs-writeback.c 2005-03-07 13:27:24.000000000 +0000
@@ -315,7 +315,7 @@ sync_sb_inodes(struct super_block *sb, s
struct backing_dev_info *bdi = mapping->backing_dev_info;
long pages_skipped;
- if (bdi->memory_backed) {
+ if (!bdi_cap_writeback_dirty(bdi)) {
list_move(&inode->i_list, &sb->s_dirty);
if (sb == blockdev_superblock) {
/*
@@ -566,7 +566,7 @@ int write_inode_now(struct inode *inode,
.sync_mode = WB_SYNC_ALL,
};
- if (inode->i_mapping->backing_dev_info->memory_backed)
+ if (!mapping_cap_writeback_dirty(inode->i_mapping))
return 0;
might_sleep();
diff -uNrp /warthog/kernels/linux-2.6.11-rc4/fs/hugetlbfs/inode.c linux-2.6.11-rc4-memback/fs/hugetlbfs/inode.c
--- /warthog/kernels/linux-2.6.11-rc4/fs/hugetlbfs/inode.c 2005-02-14 12:18:51.000000000 +0000
+++ linux-2.6.11-rc4-memback/fs/hugetlbfs/inode.c 2005-03-08 11:09:21.000000000 +0000
@@ -40,7 +40,7 @@ static struct inode_operations hugetlbfs
static struct backing_dev_info hugetlbfs_backing_dev_info = {
.ra_pages = 0, /* No readahead */
- .memory_backed = 1, /* Does not contribute to dirty memory */
+ .capabilities = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
};
int sysctl_hugetlb_shm_group;
diff -uNrp /warthog/kernels/linux-2.6.11-rc4/fs/ramfs/inode.c linux-2.6.11-rc4-memback/fs/ramfs/inode.c
--- /warthog/kernels/linux-2.6.11-rc4/fs/ramfs/inode.c 2005-02-14 12:18:53.000000000 +0000
+++ linux-2.6.11-rc4-memback/fs/ramfs/inode.c 2005-03-08 11:08:09.000000000 +0000
@@ -45,7 +45,9 @@ static struct inode_operations ramfs_dir
static struct backing_dev_info ramfs_backing_dev_info = {
.ra_pages = 0, /* No readahead */
- .memory_backed = 1, /* Does not contribute to dirty memory */
+ .capabilities = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK |
+ BDI_CAP_MAP_DIRECT | BDI_CAP_MAP_COPY |
+ BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP,
};
struct inode *ramfs_get_inode(struct super_block *sb, int mode, dev_t dev)
diff -uNrp /warthog/kernels/linux-2.6.11-rc4/fs/sysfs/inode.c linux-2.6.11-rc4-memback/fs/sysfs/inode.c
--- /warthog/kernels/linux-2.6.11-rc4/fs/sysfs/inode.c 2005-01-04 11:13:43.000000000 +0000
+++ linux-2.6.11-rc4-memback/fs/sysfs/inode.c 2005-03-08 11:12:24.000000000 +0000
@@ -23,7 +23,7 @@ static struct address_space_operations s
static struct backing_dev_info sysfs_backing_dev_info = {
.ra_pages = 0, /* No readahead */
- .memory_backed = 1, /* Does not contribute to dirty memory */
+ .capabilities = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
};
struct inode * sysfs_new_inode(mode_t mode)
diff -uNrp /warthog/kernels/linux-2.6.11-rc4/mm/filemap.c linux-2.6.11-rc4-memback/mm/filemap.c
--- /warthog/kernels/linux-2.6.11-rc4/mm/filemap.c 2005-02-14 12:19:04.000000000 +0000
+++ linux-2.6.11-rc4-memback/mm/filemap.c 2005-03-07 13:25:50.000000000 +0000
@@ -172,7 +172,7 @@ static int __filemap_fdatawrite_range(st
.end = end,
};
- if (mapping->backing_dev_info->memory_backed)
+ if (!mapping_cap_writeback_dirty(mapping))
return 0;
ret = do_writepages(mapping, &wbc);
@@ -269,7 +269,7 @@ int sync_page_range(struct inode *inode,
pgoff_t end = (pos + count - 1) >> PAGE_CACHE_SHIFT;
int ret;
- if (mapping->backing_dev_info->memory_backed || !count)
+ if (!mapping_cap_writeback_dirty(mapping) || !count)
return 0;
ret = filemap_fdatawrite_range(mapping, pos, pos + count - 1);
if (ret == 0) {
@@ -295,7 +295,7 @@ int sync_page_range_nolock(struct inode
pgoff_t end = (pos + count - 1) >> PAGE_CACHE_SHIFT;
int ret;
- if (mapping->backing_dev_info->memory_backed || !count)
+ if (!mapping_cap_writeback_dirty(mapping) || !count)
return 0;
ret = filemap_fdatawrite_range(mapping, pos, pos + count - 1);
if (ret == 0)
diff -uNrp /warthog/kernels/linux-2.6.11-rc4/mm/page-writeback.c linux-2.6.11-rc4-memback/mm/page-writeback.c
--- /warthog/kernels/linux-2.6.11-rc4/mm/page-writeback.c 2005-02-14 12:19:04.000000000 +0000
+++ linux-2.6.11-rc4-memback/mm/page-writeback.c 2005-03-07 13:26:25.000000000 +0000
@@ -605,7 +605,7 @@ int __set_page_dirty_nobuffers(struct pa
mapping2 = page_mapping(page);
if (mapping2) { /* Race with truncate? */
BUG_ON(mapping2 != mapping);
- if (!mapping->backing_dev_info->memory_backed)
+ if (mapping_cap_account_dirty(mapping))
inc_page_state(nr_dirty);
radix_tree_tag_set(&mapping->page_tree,
page_index(page), PAGECACHE_TAG_DIRTY);
@@ -691,7 +691,7 @@ int test_clear_page_dirty(struct page *p
page_index(page),
PAGECACHE_TAG_DIRTY);
spin_unlock_irqrestore(&mapping->tree_lock, flags);
- if (!mapping->backing_dev_info->memory_backed)
+ if (mapping_cap_account_dirty(mapping))
dec_page_state(nr_dirty);
return 1;
}
@@ -722,7 +722,7 @@ int clear_page_dirty_for_io(struct page
if (mapping) {
if (TestClearPageDirty(page)) {
- if (!mapping->backing_dev_info->memory_backed)
+ if (mapping_cap_account_dirty(mapping))
dec_page_state(nr_dirty);
return 1;
}
diff -uNrp /warthog/kernels/linux-2.6.11-rc4/mm/readahead.c linux-2.6.11-rc4-memback/mm/readahead.c
--- /warthog/kernels/linux-2.6.11-rc4/mm/readahead.c 2005-02-14 12:19:04.000000000 +0000
+++ linux-2.6.11-rc4-memback/mm/readahead.c 2005-03-08 11:05:04.000000000 +0000
@@ -23,6 +23,7 @@ EXPORT_SYMBOL(default_unplug_io_fn);
struct backing_dev_info default_backing_dev_info = {
.ra_pages = (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE,
.state = 0,
+ .capabilities = BDI_CAP_MAP_COPY,
.unplug_io_fn = default_unplug_io_fn,
};
EXPORT_SYMBOL_GPL(default_backing_dev_info);
diff -uNrp /warthog/kernels/linux-2.6.11-rc4/mm/shmem.c linux-2.6.11-rc4-memback/mm/shmem.c
--- /warthog/kernels/linux-2.6.11-rc4/mm/shmem.c 2005-02-14 12:19:04.000000000 +0000
+++ linux-2.6.11-rc4-memback/mm/shmem.c 2005-03-08 11:34:52.000000000 +0000
@@ -184,8 +184,8 @@ static struct vm_operations_struct shmem
static struct backing_dev_info shmem_backing_dev_info = {
.ra_pages = 0, /* No readahead */
- .memory_backed = 1, /* Does not contribute to dirty memory */
- .unplug_io_fn = default_unplug_io_fn,
+ .capabilities = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
+ .unplug_io_fn = default_unplug_io_fn,
};
static LIST_HEAD(shmem_swaplist);
diff -uNrp /warthog/kernels/linux-2.6.11-rc4/mm/swap_state.c linux-2.6.11-rc4-memback/mm/swap_state.c
--- /warthog/kernels/linux-2.6.11-rc4/mm/swap_state.c 2005-02-14 12:19:04.000000000 +0000
+++ linux-2.6.11-rc4-memback/mm/swap_state.c 2005-03-08 11:07:41.000000000 +0000
@@ -29,7 +29,7 @@ static struct address_space_operations s
};
static struct backing_dev_info swap_backing_dev_info = {
- .memory_backed = 1, /* Does not contribute to dirty memory */
+ .capabilities = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
.unplug_io_fn = swap_unplug_io_fn,
};
-
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