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make backing store use rename to atomicly replace entries file

This commit is contained in:
Vincent Sanders 2014-11-19 11:26:27 +00:00
parent 1ddf8215cf
commit a79b30bd6f
1 changed files with 38 additions and 13 deletions
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51
content/fs_backing_store.c
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@ -16,7 +16,8 @@
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/** \file
/**
* \file
* Low-level resource cache persistent storage implementation.
*
* file based backing store.
@ -64,6 +65,9 @@
/** Get store entry from ident. */
#define BS_ENTRY(ident, state) state->entries[state->addrmap[(ident) & ((1 << state->ident_bits) - 1)]]
/** Filename of serialised entries */
#define ENTRIES_FNAME "entries"
enum store_entry_flags {
STORE_ENTRY_FLAG_NONE = 0,
};
@ -699,16 +703,18 @@ build_entrymap(struct store_state *state)
/**
* Write filesystem entries to file.
*
* @todo consider atomic replace using rename.
* Serialise entry index out to storage.
*
* @param state The backing store state to read the entries from.
* @param state The backing store state to serialise.
* @return NSERROR_OK on sucess or error code on faliure.
*/
static nserror write_entries(struct store_state *state)
{
int fd;
char *fname = NULL;
ssize_t written;
char *tname = NULL; /* temporary file name for atomic replace */
char *fname = NULL; /* target filename */
size_t entries_size;
size_t written;
nserror ret;
if (state->entries_dirty == false) {
@ -716,22 +722,41 @@ static nserror write_entries(struct store_state *state)
return NSERROR_OK;
}
ret = netsurf_mkpath(&fname, NULL, 2, state->path, "entries");
ret = netsurf_mkpath(&tname, NULL, 2, state->path, "t"ENTRIES_FNAME);
if (ret != NSERROR_OK) {
return ret;
}
fd = open(fname, O_RDWR | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR);
free(fname);
fd = open(tname, O_RDWR | O_CREAT | O_TRUNC, S_IRUSR | S_IWUSR);
if (fd == -1) {
free(tname);
return NSERROR_SAVE_FAILED;
}
written = write(fd, state->entries,
state->last_entry * sizeof(struct store_entry));
entries_size = state->last_entry * sizeof(struct store_entry);
written = (size_t)write(fd, state->entries, entries_size);
close(fd);
if (written < 0) {
/** @todo Delete the file? */
/* check all data was written */
if (written != entries_size) {
unlink(tname);
free(tname);
return NSERROR_SAVE_FAILED;
}
ret = netsurf_mkpath(&fname, NULL, 2, state->path, ENTRIES_FNAME);
if (ret != NSERROR_OK) {
unlink(tname);
free(tname);
return ret;
}
if (rename(tname, fname) != 0) {
unlink(tname);
free(tname);
free(fname);
return NSERROR_SAVE_FAILED;
}
@ -753,7 +778,7 @@ read_entries(struct store_state *state)
char *fname = NULL;
nserror ret;
ret = netsurf_mkpath(&fname, NULL, 2, state->path, "entries");
ret = netsurf_mkpath(&fname, NULL, 2, state->path, ENTRIES_FNAME);
if (ret != NSERROR_OK) {
return ret;
}