Messages in this thread | | | Date | Tue, 9 Aug 2022 10:48:29 +0800 | Subject | Re: [PATCH v4] mm/page_owner.c: add llseek for page_owner | From | Kassey Li <> |
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On 8/8/2022 11:33 PM, Vlastimil Babka (SUSE) wrote: > On 8/8/22 09:36, Kassey Li wrote: >> There is usage to dump a given cma region page_owner >> instead of all page's. >> >> This change allows to specify a ppos as start_pfn >> by fseek. >> >> Any invalid ppos will be skipped, so it did not >> broken the origin dump feature. >> >> Suggested-by: Vlastimil Babka (SUSE) <vbabka@kernel.org> > > Thanks, but please change it to Vlastimil Babka <vbabka@suse.cz> > It was some mistake between me and thunderbird that it was sent from @k.o. Ok, will change it. > >> Signed-off-by: Kassey Li <quic_yingangl@quicinc.com> >> --- >> mm/page_owner.c | 20 ++++++++++++++++++-- >> 1 file changed, 18 insertions(+), 2 deletions(-) >> >> diff --git a/mm/page_owner.c b/mm/page_owner.c >> index e4c6f3f1695b..231b1877af99 100644 >> --- a/mm/page_owner.c >> +++ b/mm/page_owner.c >> @@ -497,8 +497,8 @@ read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos) >> return -EINVAL; >> >> page = NULL; >> - pfn = min_low_pfn + *ppos; >> >> + pfn = *ppos; > > Maybe we could still optimize the typical case a bit such that when it's 0, > we skip to min_low_pfn immediately. > >> /* Find a valid PFN or the start of a MAX_ORDER_NR_PAGES area */ >> while (!pfn_valid(pfn) && (pfn & (MAX_ORDER_NR_PAGES - 1)) != 0) >> pfn++; >> @@ -561,7 +561,7 @@ read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos) >> continue; >> >> /* Record the next PFN to read in the file offset */ >> - *ppos = (pfn - min_low_pfn) + 1; >> + *ppos = pfn + 1; >> >> return print_page_owner(buf, count, pfn, page, >> page_owner, handle); >> @@ -570,6 +570,21 @@ read_page_owner(struct file *file, char __user *buf, size_t count, loff_t *ppos) >> return 0; >> } >> >> +static loff_t llseek_page_owner(struct file *file, loff_t offset, int whence) >> +{ >> + loff_t retval = 0; >> + switch (whence) { >> + case SEEK_CUR: > > It's not correct for SEEK_CUR to behave like this, no? > Can we perhaps reuse the existing mem_lseek() ? agree. > > Also we should update Documentation/mm/page_owner.rst to document the lseek > support and that it works with a pfn. will do this in v5 patch set. > > Thanks! > >> + case SEEK_SET: >> + file->f_pos = offset; >> + break; >> + default: >> + retval = -ENXIO; >> + } >> + >> + return retval; >> +} >> + >> static void init_pages_in_zone(pg_data_t *pgdat, struct zone *zone) >> { >> unsigned long pfn = zone->zone_start_pfn; >> @@ -660,6 +675,7 @@ static void init_early_allocated_pages(void) >> >> static const struct file_operations proc_page_owner_operations = { >> .read = read_page_owner, >> + .llseek = llseek_page_owner, >> }; >> >> static int __init pageowner_init(void) >
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