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Reduce stack usage by vn_open() 

We should not put a 4k maxpathlen buffer on the stack, instead
locate it to the heap.  Even in user space we run ztest with 8K
This commit is contained in:
Brian Behlendorf 2010-06-29 10:14:37 -07:00
parent 428870ff73
commit edbb93c11d
3 changed files with 26 additions and 6 deletions
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From: Brian Behlendorf <behlendorf1@llnl.gov>
Subject: [PATCH] fix stack vn_open
We should not put a 4k maxpathlen buffer on the stack, instead
locate it to the heap. Even in user space we run ztest with 8K
stacks to verify correctness
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>

23
lib/libzpool/kernel.c
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@ -327,9 +327,11 @@ vn_open(char *path, int x1, int flags, int mode, vnode_t **vpp, int x2, int x3)
int fd; int fd;
vnode_t *vp; vnode_t *vp;
int old_umask; int old_umask;
char realpath[MAXPATHLEN]; char *realpath;
struct stat64 st; struct stat64 st;
realpath = umem_alloc(MAXPATHLEN, UMEM_NOFAIL);
/* /*
* If we're accessing a real disk from userland, we need to use * If we're accessing a real disk from userland, we need to use
* the character interface to avoid caching. This is particularly * the character interface to avoid caching. This is particularly
@ -343,11 +345,16 @@ vn_open(char *path, int x1, int flags, int mode, vnode_t **vpp, int x2, int x3)
if (strncmp(path, "/dev/", 5) == 0) { if (strncmp(path, "/dev/", 5) == 0) {
char *dsk; char *dsk;
fd = open64(path, O_RDONLY); fd = open64(path, O_RDONLY);
if (fd == -1) if (fd == -1) {
return (errno); err = errno;
free(realpath);
return (err);
}
if (fstat64(fd, &st) == -1) { if (fstat64(fd, &st) == -1) {
err = errno;
close(fd); close(fd);
return (errno); free(realpath);
return (err);
} }
close(fd); close(fd);
(void) sprintf(realpath, "%s", path); (void) sprintf(realpath, "%s", path);
@ -357,8 +364,11 @@ vn_open(char *path, int x1, int flags, int mode, vnode_t **vpp, int x2, int x3)
dsk + 1); dsk + 1);
} else { } else {
(void) sprintf(realpath, "%s", path); (void) sprintf(realpath, "%s", path);
if (!(flags & FCREAT) && stat64(realpath, &st) == -1) if (!(flags & FCREAT) && stat64(realpath, &st) == -1) {
return (errno); err = errno;
free(realpath);
return (err);
}
} }
if (flags & FCREAT) if (flags & FCREAT)
@ -369,6 +379,7 @@ vn_open(char *path, int x1, int flags, int mode, vnode_t **vpp, int x2, int x3)
* FREAD and FWRITE to the corresponding O_RDONLY, O_WRONLY, and O_RDWR. * FREAD and FWRITE to the corresponding O_RDONLY, O_WRONLY, and O_RDWR.
*/ */
fd = open64(realpath, flags - FREAD, mode); fd = open64(realpath, flags - FREAD, mode);
free(realpath);
if (flags & FCREAT) if (flags & FCREAT)
(void) umask(old_umask); (void) umask(old_umask);