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Commit 371d217e authored by Jan Kara's avatar Jan Kara Committed by Jens Axboe
Browse files

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



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: default avatarJan Kara <jack@suse.cz>
Signed-off-by: default avatarJens Axboe <jaxboe@fusionio.com>
parent 976e48f8

drivers/char/mem.c

+2 −1
Original line number Diff line number Diff line
@@ -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 = {

fs/char_dev.c

+3 −1
Original line number Diff line number Diff line
@@ -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;