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Date: Fri, 16 Mar 2007 17:57:26 +0100
From: Martin Peschke <mp3@...ibm.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
Wu Fengguang <wfg@...l.ustc.edu.cn>
Subject: [Patch] simplify statistics' debugfs write function
The old code was unnecessarily complex and hard to maintain.
This rewrite disposes of an issue in the old code (probably an
off-by-one bug), seen with the readahead statistics prototype patch
reported by Fengguang Wu.
Patch is against 2.6.21-rc3-mm2.
# uname -a
Linux intel 2.6.21-rc3-mm2 #3 SMP Thu Mar 8 23:28:58 CST 2007 x86_64 GNU/Linux
# echo state=on > /debug/statistics/readahead/definition
[ 694.286926] Unable to handle kernel paging request at ffff80ffa7457a5a RIP:
[ 694.287378] [<ffffffff8115228c>] strnchr+0x2c/0x40
[ 694.287946] PGD 0
[ 694.288117] Oops: 0000 [1] SMP
[ 694.288345] last sysfs file: block/hda/dev
[ 694.288624] CPU 0
[ 694.288785] Modules linked in:
[ 694.289026] Pid: 1051, comm: zsh Not tainted 2.6.21-rc3-mm2 #3
[ 694.289367] RIP: 0010:[<ffffffff8115228c>] [<ffffffff8115228c>] strnchr+0x2c/0x40
[ 694.289835] RSP: 0018:ffff810002669e28 EFLAGS: 00000217
[ 694.290147] RAX: ffff81000260bca8 RBX: ffff81000260bca8 RCX: 000000005aa5a5ae
[ 694.290456] RDX: 000000000000000a RSI: 000000005aa5a5af RDI: ffff80ffa7457a5a
[ 694.290784] RBP: ffff810002669e28 R08: 0000000000000001 R09: 0000000000000000
[ 694.291107] R10: ffff81000260bca8 R11: 0000000000000020 R12: 0000000000000008
[ 694.291452] R13: 00000000a55a5a5a R14: ffff81000260bd18 R15: ffff810002669e68
[ 694.291791] FS: 00002b33b4955e90(0000) GS:ffffffff81420000(0000) knlGS:0000000000000000
[ 694.292156] CS: 0010 DS: 0000 ES: 0000 CR0: 000000008005003b
[ 694.292420] CR2: ffff80ffa7457a5a CR3: 00000000026b6000 CR4: 00000000000006e0
[ 694.292768] Process zsh (pid: 1051, threadinfo ffff810002668000, task ffff81000262a100)
[ 694.293123] Stack: ffff810002669ea8 ffffffff8116561c 0000000000000009 ffff8100026bbe58
[ 694.293576] ffff810001ee37f8 ffff810002674e60 ffffffff813eb280 0000000000000000
[ 694.293972] ffff810002669e68 ffff810002669e68 0000000800000000 0000000000000008
[ 694.294341] Call Trace:
[ 694.294495] [<ffffffff8116561c>] statistic_def_close+0x9c/0x180
[ 694.294793] [<ffffffff81013582>] __fput+0xd2/0x1b0
[ 694.295026] [<ffffffff8102fdd4>] fput+0x14/0x20
[ 694.295253] [<ffffffff81025ca3>] filp_close+0x73/0x90
[ 694.295498] [<ffffffff8104baf8>] sys_dup2+0x148/0x190
[ 694.295752] [<ffffffff8106411e>] system_call+0x7e/0x83
Signed-off-by: Martin Peschke <mp3@...ibm.com>
---
statistic.c | 111 ++++++++++++++----------------------------------------------
1 file changed, 26 insertions(+), 85 deletions(-)
Index: linux/lib/statistic.c
===================================================================
--- linux.orig/lib/statistic.c
+++ linux/lib/statistic.c
@@ -64,8 +64,8 @@
struct statistic_file_private {
struct list_head read_seg_lh;
- struct list_head write_seg_lh;
- size_t write_seg_total_size;
+ size_t w_offset;
+ char *w_buf;
};
struct statistic_merge_private {
@@ -576,30 +576,6 @@ static void statistic_parse_line(struct
kfree(name);
}
-static void statistic_parse(struct statistic_interface *interface,
- struct list_head *line_lh, size_t line_size)
-{
- struct sgrb_seg *seg, *tmp;
- char *buf;
- int offset = 0;
-
- if (unlikely(!line_size))
- return;
- buf = kmalloc(line_size + 2, GFP_KERNEL);
- if (unlikely(!buf))
- return;
- buf[line_size] = ' ';
- buf[line_size + 1] = '\0';
- list_for_each_entry_safe(seg, tmp, line_lh, list) {
- memcpy(buf + offset, seg->address, seg->size);
- offset += seg->size;
- list_del(&seg->list);
- kfree(seg);
- }
- statistic_parse_line(interface, buf);
- kfree(buf);
-}
-
/* sequential files comprising user interface */
static int statistic_generic_open(struct inode *inode,
@@ -612,7 +588,6 @@ static int statistic_generic_open(struct
if (unlikely(!*private))
return -ENOMEM;
INIT_LIST_HEAD(&(*private)->read_seg_lh);
- INIT_LIST_HEAD(&(*private)->write_seg_lh);
file->private_data = *private;
return 0;
}
@@ -622,7 +597,6 @@ static int statistic_generic_close(struc
struct statistic_file_private *private = file->private_data;
BUG_ON(!private);
sgrb_seg_release_all(&private->read_seg_lh);
- sgrb_seg_release_all(&private->write_seg_lh);
kfree(private);
return 0;
}
@@ -658,72 +632,39 @@ static ssize_t statistic_generic_read(st
return transfered;
}
-static ssize_t statistic_generic_write(struct file *file,
- const char __user *buf, size_t len, loff_t *offset)
+static ssize_t statistic_def_write(struct file *file, const char __user *buf,
+ size_t len, loff_t *offset)
{
struct statistic_file_private *private = file->private_data;
- struct sgrb_seg *seg;
- size_t seg_residual, seg_transfer;
- size_t transfered = 0;
+ char *larger;
- BUG_ON(!private);
- if (unlikely(*offset != private->write_seg_total_size))
+ if (unlikely(*offset != private->w_offset))
return -EPIPE;
- while (len) {
- seg = sgrb_seg_find(&private->write_seg_lh, 1);
- if (unlikely(!seg))
- return -ENOMEM;
- seg_residual = seg->size - seg->offset;
- seg_transfer = min(len, seg_residual);
- if (unlikely(copy_from_user(seg->address + seg->offset,
- buf + transfered, seg_transfer)))
- return -EFAULT;
- private->write_seg_total_size += seg_transfer;
- seg->offset += seg_transfer;
- transfered += seg_transfer;
- *offset += seg_transfer;
- len -= seg_transfer;
- }
- return transfered;
+ if (*offset + len > 16 * PAGE_SIZE)
+ return -ENOMEM;
+ larger = kmalloc(*offset + len, GFP_KERNEL);
+ if (!larger)
+ return -ENOMEM;
+ memcpy(larger, private->w_buf, *offset);
+ if (copy_from_user(larger + *offset, buf, len))
+ return -EFAULT;
+ *offset += len;
+ kfree(private->w_buf);
+ private->w_buf = larger;
+ private->w_offset = *offset;
+ return len;
}
static int statistic_def_close(struct inode *inode, struct file *file)
{
struct statistic_interface *interface = inode->i_private;
struct statistic_file_private *private = file->private_data;
- struct sgrb_seg *seg, *seg_nl;
- int offset;
- LIST_HEAD(line_lh);
- char *nl;
- size_t line_size = 0;
-
- list_for_each_entry(seg, &private->write_seg_lh, list) {
- for (offset = 0; offset < seg->offset; offset += seg_nl->size) {
- seg_nl = kmalloc(sizeof(struct sgrb_seg), GFP_KERNEL);
- if (unlikely(!seg_nl))
- goto out;
- seg_nl->address = seg->address + offset;
- nl = strnchr(seg_nl->address,
- seg->offset - offset, '\n');
- if (nl) {
- seg_nl->offset = nl - seg_nl->address;
- if (seg_nl->offset)
- seg_nl->offset--;
- } else
- seg_nl->offset = seg->offset - offset;
- seg_nl->size = seg_nl->offset + 1;
- line_size += seg_nl->size;
- list_add_tail(&seg_nl->list, &line_lh);
- if (nl) {
- statistic_parse(interface, &line_lh, line_size);
- line_size = 0;
- }
- }
- }
-out:
- if (!list_empty(&line_lh))
- statistic_parse(interface, &line_lh, line_size);
- return statistic_generic_close(inode, file);
+ char *p, *q = private->w_buf;
+
+ while ((p = strsep(&q, "\n")))
+ statistic_parse_line(interface, p);
+ kfree(private->w_buf);
+ return 0;
}
static int statistic_def_open(struct inode *inode, struct file *file)
@@ -771,7 +712,7 @@ static int statistic_data_open(struct in
static struct file_operations statistic_def_fops = {
.owner = THIS_MODULE,
.read = statistic_generic_read,
- .write = statistic_generic_write,
+ .write = statistic_def_write,
.open = statistic_def_open,
.release = statistic_def_close,
};
-
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