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irmap: Revalidate irmap entries if required

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We will load some irmap entries in cache from image file,
thus producing potentially stale data in irmap cache. To
handle this, make it possible to mark the entries with
need-revalidation mark and do fstat + numbers comparison
when meeting the entry in cache.

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
This commit is contained in:
Pavel Emelyanov 2014-01-30 13:57:45 +04:00
parent 529f1a099e
commit cc731cb6da
1 changed files with 47 additions and 9 deletions
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56
irmap.c
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@ -39,7 +39,7 @@ struct irmap {
unsigned long ino;
char *path;
struct irmap *next;
bool revalidate;
int nr_kids;
struct irmap *kids;
};
@ -69,6 +69,7 @@ static int irmap_update_stat(struct irmap *i)
return -1;
}
i->revalidate = false;
i->dev = st.st_dev;
i->ino = st.st_ino;
if (!S_ISDIR(st.st_mode))
@ -172,28 +173,65 @@ static struct irmap *irmap_scan(struct irmap *t, unsigned int dev, unsigned long
return NULL;
}
static int irmap_revalidate(struct irmap *c, struct irmap **p)
{
struct stat st;
pr_debug("Revalidate stat for %s\n", c->path);
if (fstatat(mntns_root, c->path + 1, &st, AT_SYMLINK_NOFOLLOW)) {
/* File can be (re)moved, so just treat it as invalid */
pr_perror("Can't stat %s", c->path);
goto invalid;
}
if (c->dev != st.st_dev)
goto invalid;
if (c->ino != st.st_ino)
goto invalid;
c->revalidate = false;
return 0;
invalid:
pr_debug("\t%x:%lx is invalid\n", c->dev, c->ino);
*p = c->next;
xfree(c->path);
xfree(c);
return 1;
}
char *irmap_lookup(unsigned int s_dev, unsigned long i_ino)
{
struct irmap *c, *h;
struct irmap *c, *h, **p;
char *path = NULL;
int hv;
pr_debug("Resolving %x:%lx path\n", s_dev, i_ino);
hv = irmap_hashfn(s_dev, i_ino);
for (c = cache[hv]; c; c = c->next)
if (c->dev == s_dev && c->ino == i_ino) {
pr_debug("\tFound %s in cache\n", c->path);
return c->path;
}
for (p = &cache[hv]; *p; p = &(*p)->next) {
c = *p;
if (!(c->dev == s_dev && c->ino == i_ino))
continue;
if (c->revalidate && irmap_revalidate(c, p))
continue;
pr_debug("\tFound %s in cache\n", c->path);
path = c->path;
goto out;
}
for (h = hints; h->path; h++) {
pr_debug("Scanning %s hint\n", h->path);
c = irmap_scan(h, s_dev, i_ino);
if (c) {
pr_debug("\tScanned %s\n", c->path);
return c->path;
path = c->path;
goto out;
}
}
return NULL;
out:
return path;
}