From 692c0509fd0719406f8f781d9a9f2e19aa6b7c0a Mon Sep 17 00:00:00 2001 From: Andrew Morton Date: Fri, 21 Apr 2006 01:51:36 -0700 Subject: [PATCH] Simplify proc/devices and fix early termination regression Repair /proc/devices early-termination regression. 2.6.16 broke /proc/devices. An application often gets an EOF before the end of data is reached, if that application uses a series of short read(2)s to access the data. I have used read buffers of varying sizes with varying degrees of unsuccess (larger sizes get further into the data than smaller sizes, following a simple pattern). It appears that the only safe way to get the data is to use a single read buffer larger than all the data in /proc/devices. The following example demonstates the problem: # dd if=/proc/devices bs=1 Character devices: 1 mem 27+0 records in 27+0 records out This patch is a backport of the fix recently accepted to Linus's tree: commit 68eef3b4791572ecb70249c7fb145bb3742dd899 [PATCH] Simplify proc/devices and fix early termination regression It replaces the complex, state-machine algorithm introduced in 2.6.16 with a simple algorithm, modeled on the implementation of /proc/interrupts. [akpm@osdl.org: cleanups, simplifications] Signed-off-by: Joe Korty Signed-off-by: Greg Kroah-Hartman --- block/genhd.c | 103 +++++++--------------------------------------------------- 1 file changed, 11 insertions(+), 92 deletions(-) (limited to 'block') diff --git a/block/genhd.c b/block/genhd.c index db57546a709d..7f406f97c0f3 100644 --- a/block/genhd.c +++ b/block/genhd.c @@ -16,8 +16,6 @@ #include #include -#define MAX_PROBE_HASH 255 /* random */ - static struct subsystem block_subsys; static DECLARE_MUTEX(block_subsys_sem); @@ -30,108 +28,29 @@ static struct blk_major_name { struct blk_major_name *next; int major; char name[16]; -} *major_names[MAX_PROBE_HASH]; +} *major_names[BLKDEV_MAJOR_HASH_SIZE]; /* index in the above - for now: assume no multimajor ranges */ static inline int major_to_index(int major) { - return major % MAX_PROBE_HASH; -} - -struct blkdev_info { - int index; - struct blk_major_name *bd; -}; - -/* - * iterate over a list of blkdev_info structures. allows - * the major_names array to be iterated over from outside this file - * must be called with the block_subsys_sem held - */ -void *get_next_blkdev(void *dev) -{ - struct blkdev_info *info; - - if (dev == NULL) { - info = kmalloc(sizeof(*info), GFP_KERNEL); - if (!info) - goto out; - info->index=0; - info->bd = major_names[info->index]; - if (info->bd) - goto out; - } else { - info = dev; - } - - while (info->index < ARRAY_SIZE(major_names)) { - if (info->bd) - info->bd = info->bd->next; - if (info->bd) - goto out; - /* - * No devices on this chain, move to the next - */ - info->index++; - info->bd = (info->index < ARRAY_SIZE(major_names)) ? - major_names[info->index] : NULL; - if (info->bd) - goto out; - } - -out: - return info; -} - -void *acquire_blkdev_list(void) -{ - down(&block_subsys_sem); - return get_next_blkdev(NULL); -} - -void release_blkdev_list(void *dev) -{ - up(&block_subsys_sem); - kfree(dev); + return major % BLKDEV_MAJOR_HASH_SIZE; } +#ifdef CONFIG_PROC_FS -/* - * Count the number of records in the blkdev_list. - * must be called with the block_subsys_sem held - */ -int count_blkdev_list(void) +void blkdev_show(struct seq_file *f, off_t offset) { - struct blk_major_name *n; - int i, count; + struct blk_major_name *dp; - count = 0; - - for (i = 0; i < ARRAY_SIZE(major_names); i++) { - for (n = major_names[i]; n; n = n->next) - count++; + if (offset < BLKDEV_MAJOR_HASH_SIZE) { + down(&block_subsys_sem); + for (dp = major_names[offset]; dp; dp = dp->next) + seq_printf(f, "%3d %s\n", dp->major, dp->name); + up(&block_subsys_sem); } - - return count; -} - -/* - * extract the major and name values from a blkdev_info struct - * passed in as a void to *dev. Must be called with - * block_subsys_sem held - */ -int get_blkdev_info(void *dev, int *major, char **name) -{ - struct blkdev_info *info = dev; - - if (info->bd == NULL) - return 1; - - *major = info->bd->major; - *name = info->bd->name; - return 0; } +#endif /* CONFIG_PROC_FS */ int register_blkdev(unsigned int major, const char *name) { -- cgit v1.2.3