Date: Thu, 16 Feb 2023 11:56:33 GMT From: =?utf-8?Q?Jean-S=C3=A9bastien=20P=C3=A9dron?= <dumbbell@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-branches@FreeBSD.org Subject: git: 895d286a36cf - stable/13 - linuxkpi: Accept NULL as a value in `linux_xarray` Message-ID: <202302161156.31GBuXXo056366@gitrepo.freebsd.org>
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The branch stable/13 has been updated by dumbbell (ports committer): URL: https://cgit.FreeBSD.org/src/commit/?id=895d286a36cf70fa527538ca3c9a1a545f81a9cd commit 895d286a36cf70fa527538ca3c9a1a545f81a9cd Author: Jean-Sébastien Pédron <dumbbell@FreeBSD.org> AuthorDate: 2023-02-11 10:12:08 +0000 Commit: Jean-Sébastien Pédron <dumbbell@FreeBSD.org> CommitDate: 2023-02-16 11:55:20 +0000 linuxkpi: Accept NULL as a value in `linux_xarray` Linux' XArray allows to store a NULL pointer as a value. `xa_load()` would return NULL for both an unused index and an index set to NULL. But it impacts `xa_alloc()` which needs to find the next available index. However, our implementation relies on a radix tree (see `linux_radix.c`) which does not accept NULL pointers as values. I'm not sure if this is a limitation or a feature, so to work around this, a NULL value is replaced by `NULL_VALUE`, an unlikely address, when we pass it to linux_radix. Reviewed by: emaste, manu Approved by: emaste, manu Differential Revision: https://reviews.freebsd.org/D38543 (cherry picked from commit 3102ea3b15b6c3ed1ea50716d65980b680375ebc) --- sys/compat/linuxkpi/common/src/linux_xarray.c | 38 ++++++++++++++++++++++++++- 1 file changed, 37 insertions(+), 1 deletion(-) diff --git a/sys/compat/linuxkpi/common/src/linux_xarray.c b/sys/compat/linuxkpi/common/src/linux_xarray.c index a41784103852..e8a107fa6f27 100644 --- a/sys/compat/linuxkpi/common/src/linux_xarray.c +++ b/sys/compat/linuxkpi/common/src/linux_xarray.c @@ -31,6 +31,18 @@ __FBSDID("$FreeBSD$"); #include <vm/vm_pageout.h> +/* + * Linux' XArray allows to store a NULL pointer as a value. xa_load() would + * return NULL for both an unused index and an index set to NULL. But it + * impacts xa_alloc() which needs to find the next available index. + * + * However, our implementation relies on a radix tree (see `linux_radix.c`) + * which does not accept NULL pointers as values. I'm not sure this is a + * limitation or a feature, so to work around this, a NULL value is replaced by + * `NULL_VALUE`, an unlikely address, when we pass it to linux_radix. + */ +#define NULL_VALUE (void *)0x1 + /* * This function removes the element at the given index and returns * the pointer to the removed element, if any. @@ -38,9 +50,15 @@ __FBSDID("$FreeBSD$"); void * __xa_erase(struct xarray *xa, uint32_t index) { + void *retval; + XA_ASSERT_LOCKED(xa); - return (radix_tree_delete(&xa->root, index)); + retval = radix_tree_delete(&xa->root, index); + if (retval == NULL_VALUE) + retval = NULL; + + return (retval); } void * @@ -68,6 +86,9 @@ xa_load(struct xarray *xa, uint32_t index) retval = radix_tree_lookup(&xa->root, index); xa_unlock(xa); + if (retval == NULL_VALUE) + retval = NULL; + return (retval); } @@ -109,6 +130,8 @@ __xa_alloc(struct xarray *xa, uint32_t *pindex, void *ptr, uint32_t mask, gfp_t MPASS((mask & (mask + 1)) == 0); *pindex = (xa->flags & XA_FLAGS_ALLOC1) != 0 ? 1 : 0; + if (ptr == NULL) + ptr = NULL_VALUE; retry: retval = radix_tree_insert(&xa->root, *pindex, ptr); @@ -137,6 +160,9 @@ xa_alloc(struct xarray *xa, uint32_t *pindex, void *ptr, uint32_t mask, gfp_t gf { int retval; + if (ptr == NULL) + ptr = NULL_VALUE; + xa_lock(xa); retval = __xa_alloc(xa, pindex, ptr, mask, gfp); xa_unlock(xa); @@ -166,6 +192,8 @@ __xa_alloc_cyclic(struct xarray *xa, uint32_t *pindex, void *ptr, uint32_t mask, MPASS((mask & (mask + 1)) == 0); *pnext_index = (xa->flags & XA_FLAGS_ALLOC1) != 0 ? 1 : 0; + if (ptr == NULL) + ptr = NULL_VALUE; retry: retval = radix_tree_insert(&xa->root, *pnext_index, ptr); @@ -220,6 +248,8 @@ __xa_insert(struct xarray *xa, uint32_t index, void *ptr, gfp_t gfp) int retval; XA_ASSERT_LOCKED(xa); + if (ptr == NULL) + ptr = NULL_VALUE; retry: retval = radix_tree_insert(&xa->root, index, ptr); @@ -262,11 +292,15 @@ __xa_store(struct xarray *xa, uint32_t index, void *ptr, gfp_t gfp) int retval; XA_ASSERT_LOCKED(xa); + if (ptr == NULL) + ptr = NULL_VALUE; retry: retval = radix_tree_store(&xa->root, index, &ptr); switch (retval) { case 0: + if (ptr == NULL_VALUE) + ptr = NULL; break; case -ENOMEM: if (likely(gfp & M_WAITOK)) { @@ -374,6 +408,8 @@ __xa_next(struct xarray *xa, unsigned long *pindex, bool not_first) found = radix_tree_iter_find(&xa->root, &iter, &ppslot); if (likely(found)) { retval = *ppslot; + if (retval == NULL_VALUE) + retval = NULL; *pindex = iter.index; } else { retval = NULL;
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