From cbc02854331edc6dc22d8b77b6e22e38ebc7dd51 Mon Sep 17 00:00:00 2001 From: "Matthew Wilcox (Oracle)" Date: Wed, 26 Jul 2023 22:58:17 -0400 Subject: XArray: Do not return sibling entries from xa_load() It is possible for xa_load() to observe a sibling entry pointing to another sibling entry. An example: Thread A: Thread B: xa_store_range(xa, entry, 188, 191, gfp); xa_load(xa, 191); entry = xa_entry(xa, node, 63); [entry is a sibling of 188] xa_store_range(xa, entry, 184, 191, gfp); if (xa_is_sibling(entry)) offset = xa_to_sibling(entry); entry = xa_entry(xas->xa, node, offset); [entry is now a sibling of 184] It is sufficient to go around this loop until we hit a non-sibling entry. Sibling entries always point earlier in the node, so we are guaranteed to terminate this search. Signed-off-by: Matthew Wilcox (Oracle) Fixes: 6b24ca4a1a8d ("mm: Use multi-index entries in the page cache") Cc: stable@vger.kernel.org --- lib/xarray.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'lib') diff --git a/lib/xarray.c b/lib/xarray.c index 2071a3718f4e..142e36f9dfda 100644 --- a/lib/xarray.c +++ b/lib/xarray.c @@ -206,7 +206,7 @@ static void *xas_descend(struct xa_state *xas, struct xa_node *node) void *entry = xa_entry(xas->xa, node, offset); xas->xa_node = node; - if (xa_is_sibling(entry)) { + while (xa_is_sibling(entry)) { offset = xa_to_sibling(entry); entry = xa_entry(xas->xa, node, offset); if (node->shift && xa_is_node(entry)) -- cgit v1.2.3-58-ga151 From e7716c74e3882405f9eca16faa6cb1bf19995399 Mon Sep 17 00:00:00 2001 From: Philipp Stanner Date: Mon, 21 Aug 2023 10:21:29 +0200 Subject: xarray: Document necessary flag in alloc functions Adds a new line to the docstrings of functions wrapping __xa_alloc() and __xa_alloc_cyclic(), informing about the necessity of flag XA_FLAGS_ALLOC being set previously. The documentation so far says that functions wrapping __xa_alloc() and __xa_alloc_cyclic() are supposed to return either -ENOMEM or -EBUSY in case of an error. If the xarray has been initialized without the flag XA_FLAGS_ALLOC, however, they fail with a different, undocumented error code. As hinted at in Documentation/core-api/xarray.rst, wrappers around these functions should only be invoked when the flag has been set. The functions' documentation should reflect that as well. Signed-off-by: Philipp Stanner Signed-off-by: Matthew Wilcox (Oracle) --- include/linux/xarray.h | 18 ++++++++++++++++++ lib/xarray.c | 6 ++++++ 2 files changed, 24 insertions(+) (limited to 'lib') diff --git a/include/linux/xarray.h b/include/linux/xarray.h index 741703b45f61..cb571dfcf4b1 100644 --- a/include/linux/xarray.h +++ b/include/linux/xarray.h @@ -856,6 +856,9 @@ static inline int __must_check xa_insert_irq(struct xarray *xa, * stores the index into the @id pointer, then stores the entry at * that index. A concurrent lookup will not see an uninitialised @id. * + * Must only be operated on an xarray initialized with flag XA_FLAGS_ALLOC set + * in xa_init_flags(). + * * Context: Any context. Takes and releases the xa_lock. May sleep if * the @gfp flags permit. * Return: 0 on success, -ENOMEM if memory could not be allocated or @@ -886,6 +889,9 @@ static inline __must_check int xa_alloc(struct xarray *xa, u32 *id, * stores the index into the @id pointer, then stores the entry at * that index. A concurrent lookup will not see an uninitialised @id. * + * Must only be operated on an xarray initialized with flag XA_FLAGS_ALLOC set + * in xa_init_flags(). + * * Context: Any context. Takes and releases the xa_lock while * disabling softirqs. May sleep if the @gfp flags permit. * Return: 0 on success, -ENOMEM if memory could not be allocated or @@ -916,6 +922,9 @@ static inline int __must_check xa_alloc_bh(struct xarray *xa, u32 *id, * stores the index into the @id pointer, then stores the entry at * that index. A concurrent lookup will not see an uninitialised @id. * + * Must only be operated on an xarray initialized with flag XA_FLAGS_ALLOC set + * in xa_init_flags(). + * * Context: Process context. Takes and releases the xa_lock while * disabling interrupts. May sleep if the @gfp flags permit. * Return: 0 on success, -ENOMEM if memory could not be allocated or @@ -949,6 +958,9 @@ static inline int __must_check xa_alloc_irq(struct xarray *xa, u32 *id, * The search for an empty entry will start at @next and will wrap * around if necessary. * + * Must only be operated on an xarray initialized with flag XA_FLAGS_ALLOC set + * in xa_init_flags(). + * * Context: Any context. Takes and releases the xa_lock. May sleep if * the @gfp flags permit. * Return: 0 if the allocation succeeded without wrapping. 1 if the @@ -983,6 +995,9 @@ static inline int xa_alloc_cyclic(struct xarray *xa, u32 *id, void *entry, * The search for an empty entry will start at @next and will wrap * around if necessary. * + * Must only be operated on an xarray initialized with flag XA_FLAGS_ALLOC set + * in xa_init_flags(). + * * Context: Any context. Takes and releases the xa_lock while * disabling softirqs. May sleep if the @gfp flags permit. * Return: 0 if the allocation succeeded without wrapping. 1 if the @@ -1017,6 +1032,9 @@ static inline int xa_alloc_cyclic_bh(struct xarray *xa, u32 *id, void *entry, * The search for an empty entry will start at @next and will wrap * around if necessary. * + * Must only be operated on an xarray initialized with flag XA_FLAGS_ALLOC set + * in xa_init_flags(). + * * Context: Process context. Takes and releases the xa_lock while * disabling interrupts. May sleep if the @gfp flags permit. * Return: 0 if the allocation succeeded without wrapping. 1 if the diff --git a/lib/xarray.c b/lib/xarray.c index 142e36f9dfda..39f07bfc4dcc 100644 --- a/lib/xarray.c +++ b/lib/xarray.c @@ -1802,6 +1802,9 @@ EXPORT_SYMBOL(xa_get_order); * stores the index into the @id pointer, then stores the entry at * that index. A concurrent lookup will not see an uninitialised @id. * + * Must only be operated on an xarray initialized with flag XA_FLAGS_ALLOC set + * in xa_init_flags(). + * * Context: Any context. Expects xa_lock to be held on entry. May * release and reacquire xa_lock if @gfp flags permit. * Return: 0 on success, -ENOMEM if memory could not be allocated or @@ -1850,6 +1853,9 @@ EXPORT_SYMBOL(__xa_alloc); * The search for an empty entry will start at @next and will wrap * around if necessary. * + * Must only be operated on an xarray initialized with flag XA_FLAGS_ALLOC set + * in xa_init_flags(). + * * Context: Any context. Expects xa_lock to be held on entry. May * release and reacquire xa_lock if @gfp flags permit. * Return: 0 if the allocation succeeded without wrapping. 1 if the -- cgit v1.2.3-58-ga151 From 2a15de80dd0f7e04a823291aa9eb49c5294f56af Mon Sep 17 00:00:00 2001 From: Ariel Marcovitch Date: Sat, 26 Aug 2023 20:33:17 +0300 Subject: idr: fix param name in idr_alloc_cyclic() doc The relevant parameter is 'start' and not 'nextid' Fixes: 460488c58ca8 ("idr: Remove idr_alloc_ext") Signed-off-by: Ariel Marcovitch Signed-off-by: Matthew Wilcox (Oracle) --- lib/idr.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'lib') diff --git a/lib/idr.c b/lib/idr.c index 7ecdfdb5309e..13f2758c2377 100644 --- a/lib/idr.c +++ b/lib/idr.c @@ -100,7 +100,7 @@ EXPORT_SYMBOL_GPL(idr_alloc); * @end: The maximum ID (exclusive). * @gfp: Memory allocation flags. * - * Allocates an unused ID in the range specified by @nextid and @end. If + * Allocates an unused ID in the range specified by @start and @end. If * @end is <= 0, it is treated as one larger than %INT_MAX. This allows * callers to use @start + N as @end as long as N is within integer range. * The search for an unused ID will start at the last ID allocated and will -- cgit v1.2.3-58-ga151