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char: Mark /dev/zero and /dev/kmem as not capable of writeback

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These devices don't do any writeback but their device inodes still can get
dirty so mark bdi appropriately so that bdi code does the right thing and files
inodes to lists of bdi carrying the device inodes.

Cc: stable@kernel.org
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
This commit is contained in:
Jan Kara 2010-09-21 11:49:01 +02:00 committed by Jens Axboe
parent 976e48f8a5
commit 371d217ee1
2 changed files with 5 additions and 2 deletions
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3
drivers/char/mem.c
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@ -788,10 +788,11 @@ static const struct file_operations zero_fops = {
/*
* capabilities for /dev/zero
* - permits private mappings, "copies" are taken of the source of zeros
* - no writeback happens
*/
static struct backing_dev_info zero_bdi = {
.name = "char/mem",
.capabilities = BDI_CAP_MAP_COPY,
.capabilities = BDI_CAP_MAP_COPY | BDI_CAP_NO_ACCT_AND_WRITEBACK,
};
static const struct file_operations full_fops = {

4
fs/char_dev.c
View file

@ -40,7 +40,9 @@ struct backing_dev_info directly_mappable_cdev_bdi = {
#endif
/* permit direct mmap, for read, write or exec */
BDI_CAP_MAP_DIRECT |
BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP),
BDI_CAP_READ_MAP | BDI_CAP_WRITE_MAP | BDI_CAP_EXEC_MAP |
/* no writeback happens */
BDI_CAP_NO_ACCT_AND_WRITEBACK),
};
static struct kobj_map *cdev_map;