From: Andrew Morton Date: Fri, 21 Apr 2006 08:51:36 +0000 (-0700) Subject: [PATCH] Simplify proc/devices and fix early termination regression X-Git-Url: http://www.kernel.org/git/?p=linux/kernel/git/stable/linux-2.6.16.y.git;a=commitdiff;h=692c0509fd0719406f8f781d9a9f2e19aa6b7c0a [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 --- --- 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; - - count = 0; + struct blk_major_name *dp; - 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) { --- a/fs/char_dev.c +++ b/fs/char_dev.c @@ -15,6 +15,7 @@ #include #include #include +#include #include #include @@ -26,8 +27,6 @@ static struct kobj_map *cdev_map; -#define MAX_PROBE_HASH 255 /* random */ - static DECLARE_MUTEX(chrdevs_lock); static struct char_device_struct { @@ -38,93 +37,29 @@ static struct char_device_struct { char name[64]; struct file_operations *fops; struct cdev *cdev; /* will die */ -} *chrdevs[MAX_PROBE_HASH]; +} *chrdevs[CHRDEV_MAJOR_HASH_SIZE]; /* index in the above */ static inline int major_to_index(int major) { - return major % MAX_PROBE_HASH; -} - -struct chrdev_info { - int index; - struct char_device_struct *cd; -}; - -void *get_next_chrdev(void *dev) -{ - struct chrdev_info *info; - - if (dev == NULL) { - info = kmalloc(sizeof(*info), GFP_KERNEL); - if (!info) - goto out; - info->index=0; - info->cd = chrdevs[info->index]; - if (info->cd) - goto out; - } else { - info = dev; - } - - while (info->index < ARRAY_SIZE(chrdevs)) { - if (info->cd) - info->cd = info->cd->next; - if (info->cd) - goto out; - /* - * No devices on this chain, move to the next - */ - info->index++; - info->cd = (info->index < ARRAY_SIZE(chrdevs)) ? - chrdevs[info->index] : NULL; - if (info->cd) - goto out; - } - -out: - return info; -} - -void *acquire_chrdev_list(void) -{ - down(&chrdevs_lock); - return get_next_chrdev(NULL); -} - -void release_chrdev_list(void *dev) -{ - up(&chrdevs_lock); - kfree(dev); + return major % CHRDEV_MAJOR_HASH_SIZE; } +#ifdef CONFIG_PROC_FS -int count_chrdev_list(void) +void chrdev_show(struct seq_file *f, off_t offset) { struct char_device_struct *cd; - int i, count; - - count = 0; - for (i = 0; i < ARRAY_SIZE(chrdevs) ; i++) { - for (cd = chrdevs[i]; cd; cd = cd->next) - count++; + if (offset < CHRDEV_MAJOR_HASH_SIZE) { + down(&chrdevs_lock); + for (cd = chrdevs[offset]; cd; cd = cd->next) + seq_printf(f, "%3d %s\n", cd->major, cd->name); + up(&chrdevs_lock); } - - return count; } -int get_chrdev_info(void *dev, int *major, char **name) -{ - struct chrdev_info *info = dev; - - if (info->cd == NULL) - return 1; - - *major = info->cd->major; - *name = info->cd->name; - return 0; -} +#endif /* CONFIG_PROC_FS */ /* * Register a single major with a specified minor range. --- a/fs/proc/proc_misc.c +++ b/fs/proc/proc_misc.c @@ -249,144 +249,60 @@ static int cpuinfo_open(struct inode *in return seq_open(file, &cpuinfo_op); } -enum devinfo_states { - CHR_HDR, - CHR_LIST, - BLK_HDR, - BLK_LIST, - DEVINFO_DONE -}; - -struct devinfo_state { - void *chrdev; - void *blkdev; - unsigned int num_records; - unsigned int cur_record; - enum devinfo_states state; +static struct file_operations proc_cpuinfo_operations = { + .open = cpuinfo_open, + .read = seq_read, + .llseek = seq_lseek, + .release = seq_release, }; -static void *devinfo_start(struct seq_file *f, loff_t *pos) +static int devinfo_show(struct seq_file *f, void *v) { - struct devinfo_state *info = f->private; + int i = *(loff_t *) v; - if (*pos) { - if ((info) && (*pos <= info->num_records)) - return info; - return NULL; + if (i < CHRDEV_MAJOR_HASH_SIZE) { + if (i == 0) + seq_printf(f, "Character devices:\n"); + chrdev_show(f, i); + } else { + i -= CHRDEV_MAJOR_HASH_SIZE; + if (i == 0) + seq_printf(f, "\nBlock devices:\n"); + blkdev_show(f, i); } - info = kmalloc(sizeof(*info), GFP_KERNEL); - f->private = info; - info->chrdev = acquire_chrdev_list(); - info->blkdev = acquire_blkdev_list(); - info->state = CHR_HDR; - info->num_records = count_chrdev_list(); - info->num_records += count_blkdev_list(); - info->num_records += 2; /* Character and Block headers */ - *pos = 1; - info->cur_record = *pos; - return info; + return 0; } -static void *devinfo_next(struct seq_file *f, void *v, loff_t *pos) +static void *devinfo_start(struct seq_file *f, loff_t *pos) { - int idummy; - char *ndummy; - struct devinfo_state *info = f->private; - - switch (info->state) { - case CHR_HDR: - info->state = CHR_LIST; - (*pos)++; - /*fallthrough*/ - case CHR_LIST: - if (get_chrdev_info(info->chrdev,&idummy,&ndummy)) { - /* - * The character dev list is complete - */ - info->state = BLK_HDR; - } else { - info->chrdev = get_next_chrdev(info->chrdev); - } - (*pos)++; - break; - case BLK_HDR: - info->state = BLK_LIST; - (*pos)++; - /*fallthrough*/ - case BLK_LIST: - if (get_blkdev_info(info->blkdev,&idummy,&ndummy)) { - /* - * The block dev list is complete - */ - info->state = DEVINFO_DONE; - } else { - info->blkdev = get_next_blkdev(info->blkdev); - } - (*pos)++; - break; - case DEVINFO_DONE: - (*pos)++; - info->cur_record = *pos; - info = NULL; - break; - default: - break; - } - if (info) - info->cur_record = *pos; - return info; + if (*pos < (BLKDEV_MAJOR_HASH_SIZE + CHRDEV_MAJOR_HASH_SIZE)) + return pos; + return NULL; } -static void devinfo_stop(struct seq_file *f, void *v) +static void *devinfo_next(struct seq_file *f, void *v, loff_t *pos) { - struct devinfo_state *info = f->private; - - if (info) { - release_chrdev_list(info->chrdev); - release_blkdev_list(info->blkdev); - f->private = NULL; - kfree(info); - } + (*pos)++; + if (*pos >= (BLKDEV_MAJOR_HASH_SIZE + CHRDEV_MAJOR_HASH_SIZE)) + return NULL; + return pos; } -static int devinfo_show(struct seq_file *f, void *arg) +static void devinfo_stop(struct seq_file *f, void *v) { - int major; - char *name; - struct devinfo_state *info = f->private; - - switch(info->state) { - case CHR_HDR: - seq_printf(f,"Character devices:\n"); - /* fallthrough */ - case CHR_LIST: - if (!get_chrdev_info(info->chrdev,&major,&name)) - seq_printf(f,"%3d %s\n",major,name); - break; - case BLK_HDR: - seq_printf(f,"\nBlock devices:\n"); - /* fallthrough */ - case BLK_LIST: - if (!get_blkdev_info(info->blkdev,&major,&name)) - seq_printf(f,"%3d %s\n",major,name); - break; - default: - break; - } - - return 0; + /* Nothing to do */ } -static struct seq_operations devinfo_op = { - .start = devinfo_start, - .next = devinfo_next, - .stop = devinfo_stop, - .show = devinfo_show, +static struct seq_operations devinfo_ops = { + .start = devinfo_start, + .next = devinfo_next, + .stop = devinfo_stop, + .show = devinfo_show }; -static int devinfo_open(struct inode *inode, struct file *file) +static int devinfo_open(struct inode *inode, struct file *filp) { - return seq_open(file, &devinfo_op); + return seq_open(filp, &devinfo_ops); } static struct file_operations proc_devinfo_operations = { @@ -396,13 +312,6 @@ static struct file_operations proc_devin .release = seq_release, }; -static struct file_operations proc_cpuinfo_operations = { - .open = cpuinfo_open, - .read = seq_read, - .llseek = seq_lseek, - .release = seq_release, -}; - extern struct seq_operations vmstat_op; static int vmstat_open(struct inode *inode, struct file *file) { --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -1383,6 +1383,7 @@ extern int bd_claim(struct block_device extern void bd_release(struct block_device *); /* fs/char_dev.c */ +#define CHRDEV_MAJOR_HASH_SIZE 255 extern int alloc_chrdev_region(dev_t *, unsigned, unsigned, const char *); extern int register_chrdev_region(dev_t, unsigned, const char *); extern int register_chrdev(unsigned int, const char *, @@ -1390,25 +1391,17 @@ extern int register_chrdev(unsigned int, extern int unregister_chrdev(unsigned int, const char *); extern void unregister_chrdev_region(dev_t, unsigned); extern int chrdev_open(struct inode *, struct file *); -extern int get_chrdev_list(char *); -extern void *acquire_chrdev_list(void); -extern int count_chrdev_list(void); -extern void *get_next_chrdev(void *); -extern int get_chrdev_info(void *, int *, char **); -extern void release_chrdev_list(void *); +extern void chrdev_show(struct seq_file *,off_t); /* fs/block_dev.c */ +#define BLKDEV_MAJOR_HASH_SIZE 255 #define BDEVNAME_SIZE 32 /* Largest string for a blockdev identifier */ extern const char *__bdevname(dev_t, char *buffer); extern const char *bdevname(struct block_device *bdev, char *buffer); extern struct block_device *lookup_bdev(const char *); extern struct block_device *open_bdev_excl(const char *, int, void *); extern void close_bdev_excl(struct block_device *); -extern void *acquire_blkdev_list(void); -extern int count_blkdev_list(void); -extern void *get_next_blkdev(void *); -extern int get_blkdev_info(void *, int *, char **); -extern void release_blkdev_list(void *); +extern void blkdev_show(struct seq_file *,off_t); extern void init_special_inode(struct inode *, umode_t, dev_t);