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Commit 8c7a8d1c authored by Bart Van Assche's avatar Bart Van Assche Committed by Jens Axboe
Browse files

lib/scatterlist: Fix chaining support in sgl_alloc_order() 



This patch avoids that workloads with large block sizes (megabytes)
can trigger the following call stack with the ib_srpt driver (that
driver is the only driver that chains scatterlists allocated by
sgl_alloc_order()):

BUG: Bad page state in process kworker/0:1H  pfn:2423a78
page:fffffb03d08e9e00 count:-3 mapcount:0 mapping:          (null) index:0x0
flags: 0x57ffffc0000000()
raw: 0057ffffc0000000 0000000000000000 0000000000000000 fffffffdffffffff
raw: dead000000000100 dead000000000200 0000000000000000 0000000000000000
page dumped because: nonzero _count
CPU: 0 PID: 733 Comm: kworker/0:1H Tainted: G          I      4.15.0-rc7.bart+ #1
Hardware name: HP ProLiant DL380 G7, BIOS P67 08/16/2015
Workqueue: ib-comp-wq ib_cq_poll_work [ib_core]
Call Trace:
 dump_stack+0x5c/0x83
 bad_page+0xf5/0x10f
 get_page_from_freelist+0xa46/0x11b0
 __alloc_pages_nodemask+0x103/0x290
 sgl_alloc_order+0x101/0x180
 target_alloc_sgl+0x2c/0x40 [target_core_mod]
 srpt_alloc_rw_ctxs+0x173/0x2d0 [ib_srpt]
 srpt_handle_new_iu+0x61e/0x7f0 [ib_srpt]
 __ib_process_cq+0x55/0xa0 [ib_core]
 ib_cq_poll_work+0x1b/0x60 [ib_core]
 process_one_work+0x141/0x340
 worker_thread+0x47/0x3e0
 kthread+0xf5/0x130
 ret_from_fork+0x1f/0x30

Fixes: e80a0af4 ("lib/scatterlist: Introduce sgl_alloc() and sgl_free()")
Reported-by: default avatarLaurence Oberman <loberman@redhat.com>
Tested-by: default avatarLaurence Oberman <loberman@redhat.com>
Signed-off-by: default avatarBart Van Assche <bart.vanassche@wdc.com>
Cc: Nicholas A. Bellinger <nab@linux-iscsi.org>
Cc: Laurence Oberman <loberman@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 9b9c63f7

drivers/target/target_core_transport.c

+1 −1
Original line number Diff line number Diff line
@@ -2300,7 +2300,7 @@ static void target_complete_ok_work(struct work_struct *work) 


void target_free_sgl(struct scatterlist *sgl, int nents)

{

	sgl_free(sgl);

	sgl_free_n_order(sgl, nents, 0);

}

EXPORT_SYMBOL(target_free_sgl);

include/linux/scatterlist.h

+1 −0
Original line number Diff line number Diff line
@@ -282,6 +282,7 @@ struct scatterlist *sgl_alloc_order(unsigned long long length, 
				    gfp_t gfp, unsigned int *nent_p);

struct scatterlist *sgl_alloc(unsigned long long length, gfp_t gfp,

			      unsigned int *nent_p);

void sgl_free_n_order(struct scatterlist *sgl, int nents, int order);

void sgl_free_order(struct scatterlist *sgl, int order);

void sgl_free(struct scatterlist *sgl);

#endif /* CONFIG_SGL_ALLOC */

lib/scatterlist.c

+27 −5
Original line number Diff line number Diff line
@@ -512,7 +512,7 @@ struct scatterlist *sgl_alloc_order(unsigned long long length, 
	if (!sgl)

		return NULL;



	sg_init_table(sgl, nent);

	sg_init_table(sgl, nalloc);

	sg = sgl;

	while (length) {

		elem_len = min_t(u64, length, PAGE_SIZE << order);
@@ -526,7 +526,7 @@ struct scatterlist *sgl_alloc_order(unsigned long long length, 
		length -= elem_len;

		sg = sg_next(sg);

	}

	WARN_ON_ONCE(sg);

	WARN_ONCE(length, "length = %lld\n", length);

	if (nent_p)

		*nent_p = nent;

	return sgl;
@@ -549,22 +549,44 @@ struct scatterlist *sgl_alloc(unsigned long long length, gfp_t gfp, 
EXPORT_SYMBOL(sgl_alloc);



/**

 * sgl_free_order - free a scatterlist and its pages

 * sgl_free_n_order - free a scatterlist and its pages

 * @sgl: Scatterlist with one or more elements

 * @nents: Maximum number of elements to free

 * @order: Second argument for __free_pages()

 *

 * Notes:

 * - If several scatterlists have been chained and each chain element is

 *   freed separately then it's essential to set nents correctly to avoid that a

 *   page would get freed twice.

 * - All pages in a chained scatterlist can be freed at once by setting @nents

 *   to a high number.

 */

void sgl_free_order(struct scatterlist *sgl, int order)

void sgl_free_n_order(struct scatterlist *sgl, int nents, int order)

{

	struct scatterlist *sg;

	struct page *page;

	int i;



	for (sg = sgl; sg; sg = sg_next(sg)) {

	for_each_sg(sgl, sg, nents, i) {

		if (!sg)

			break;

		page = sg_page(sg);

		if (page)

			__free_pages(page, order);

	}

	kfree(sgl);

}

EXPORT_SYMBOL(sgl_free_n_order);



/**

 * sgl_free_order - free a scatterlist and its pages

 * @sgl: Scatterlist with one or more elements

 * @order: Second argument for __free_pages()

 */

void sgl_free_order(struct scatterlist *sgl, int order)

{

	sgl_free_n_order(sgl, INT_MAX, order);

}

EXPORT_SYMBOL(sgl_free_order);



/**