Commit 11d763f0 authored by Andreas Gruenbacher's avatar Andreas Gruenbacher
Browse files

gfs2: Retries missing in gfs2_{rename,exchange} 



Fix a bug in gfs2's asynchronous glock handling for rename and exchange
operations.  The original async implementation from commit ad26967b
("gfs2: Use async glocks for rename") mentioned that retries were needed
but never implemented them, causing operations to fail with -ESTALE
instead of retrying on timeout.

Also makes the waiting interruptible.

In addition, the timeouts used were too high for situations in which
timing out is a rare but expected scenario.  Switch to shorter timeouts
with randomization and exponentional backoff.

Fixes: ad26967b ("gfs2: Use async glocks for rename")
Signed-off-by: default avatarAndreas Gruenbacher <agruenba@redhat.com>
parent f8f04248

fs/gfs2/glock.c

+27 −9
Original line number Diff line number Diff line
@@ -1284,31 +1284,45 @@ static int glocks_pending(unsigned int num_gh, struct gfs2_holder *ghs) 
 * gfs2_glock_async_wait - wait on multiple asynchronous glock acquisitions

 * @num_gh: the number of holders in the array

 * @ghs: the glock holder array

 * @retries: number of retries attempted so far

 *

 * Returns: 0 on success, meaning all glocks have been granted and are held.

 *          -ESTALE if the request timed out, meaning all glocks were released,

 *          and the caller should retry the operation.

 */



int gfs2_glock_async_wait(unsigned int num_gh, struct gfs2_holder *ghs)

int gfs2_glock_async_wait(unsigned int num_gh, struct gfs2_holder *ghs,

			  unsigned int retries)

{

	struct gfs2_sbd *sdp = ghs[0].gh_gl->gl_name.ln_sbd;

	int i, ret = 0, timeout = 0;

	unsigned long start_time = jiffies;

	int i, ret = 0;

	long timeout;



	might_sleep();

	/*

	 * Total up the (minimum hold time * 2) of all glocks and use that to

	 * determine the max amount of time we should wait.

	 */

	for (i = 0; i < num_gh; i++)

		timeout += ghs[i].gh_gl->gl_hold_time << 1;



	if (!wait_event_timeout(sdp->sd_async_glock_wait,

	timeout = GL_GLOCK_MIN_HOLD;

	if (retries) {

		unsigned int max_shift;

		long incr;



		/* Add a random delay and increase the timeout exponentially. */

		max_shift = BITS_PER_LONG - 2 - __fls(GL_GLOCK_HOLD_INCR);

		incr = min(GL_GLOCK_HOLD_INCR << min(retries - 1, max_shift),

			   10 * HZ - GL_GLOCK_MIN_HOLD);

		schedule_timeout_interruptible(get_random_long() % (incr / 3));

		if (signal_pending(current))

			goto interrupted;

		timeout += (incr / 3) + get_random_long() % (incr / 3);

	}



	if (!wait_event_interruptible_timeout(sdp->sd_async_glock_wait,

				!glocks_pending(num_gh, ghs), timeout)) {

		ret = -ESTALE; /* request timed out. */

		goto out;

	}

	if (signal_pending(current))

		goto interrupted;



	for (i = 0; i < num_gh; i++) {

		struct gfs2_holder *gh = &ghs[i];
@@ -1332,6 +1346,10 @@ int gfs2_glock_async_wait(unsigned int num_gh, struct gfs2_holder *ghs) 
		}

	}

	return ret;



interrupted:

	ret = -EINTR;

	goto out;

}



/**

fs/gfs2/glock.h

+2 −1
Original line number Diff line number Diff line
@@ -204,7 +204,8 @@ int gfs2_glock_poll(struct gfs2_holder *gh); 
int gfs2_instantiate(struct gfs2_holder *gh);

int gfs2_glock_holder_ready(struct gfs2_holder *gh);

int gfs2_glock_wait(struct gfs2_holder *gh);

int gfs2_glock_async_wait(unsigned int num_gh, struct gfs2_holder *ghs);

int gfs2_glock_async_wait(unsigned int num_gh, struct gfs2_holder *ghs,

			  unsigned int retries);

void gfs2_glock_dq(struct gfs2_holder *gh);

void gfs2_glock_dq_wait(struct gfs2_holder *gh);

void gfs2_glock_dq_uninit(struct gfs2_holder *gh);

fs/gfs2/inode.c

+14 −4
Original line number Diff line number Diff line
@@ -1495,7 +1495,7 @@ static int gfs2_rename(struct inode *odir, struct dentry *odentry, 
	unsigned int num_gh;

	int dir_rename = 0;

	struct gfs2_diradd da = { .nr_blocks = 0, .save_loc = 0, };

	unsigned int x;

	unsigned int retries = 0, x;

	int error;



	gfs2_holder_mark_uninitialized(&r_gh);
@@ -1545,12 +1545,17 @@ static int gfs2_rename(struct inode *odir, struct dentry *odentry, 
		num_gh++;

	}



again:

	for (x = 0; x < num_gh; x++) {

		error = gfs2_glock_nq(ghs + x);

		if (error)

			goto out_gunlock;

	}

	error = gfs2_glock_async_wait(num_gh, ghs);

	error = gfs2_glock_async_wait(num_gh, ghs, retries);

	if (error == -ESTALE) {

		retries++;

		goto again;

	}

	if (error)

		goto out_gunlock;
@@ -1739,7 +1744,7 @@ static int gfs2_exchange(struct inode *odir, struct dentry *odentry, 
	struct gfs2_sbd *sdp = GFS2_SB(odir);

	struct gfs2_holder ghs[4], r_gh;

	unsigned int num_gh;

	unsigned int x;

	unsigned int retries = 0, x;

	umode_t old_mode = oip->i_inode.i_mode;

	umode_t new_mode = nip->i_inode.i_mode;

	int error;
@@ -1783,13 +1788,18 @@ static int gfs2_exchange(struct inode *odir, struct dentry *odentry, 
	gfs2_holder_init(nip->i_gl, LM_ST_EXCLUSIVE, GL_ASYNC, ghs + num_gh);

	num_gh++;



again:

	for (x = 0; x < num_gh; x++) {

		error = gfs2_glock_nq(ghs + x);

		if (error)

			goto out_gunlock;

	}



	error = gfs2_glock_async_wait(num_gh, ghs);

	error = gfs2_glock_async_wait(num_gh, ghs, retries);

	if (error == -ESTALE) {

		retries++;

		goto again;

	}

	if (error)

		goto out_gunlock;